nwdsm section 04 - civil engineering_a5 (18 apr 2013).pdf

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Section 4: Civil Engineering D/MTRC/NW/DSM/ST/400/A5

NWDSM-Section 4(Cover)-A5 April 2013

New Works Design Standards ManualSection 4: Civil EngineeringRevision Record Sheet

Version Date of Issue

ClauseNo(s)

Brief Description of Change ApprovedBy

A1 Jan 1997 All First issue PEM

A2 Apr 1997 All Underground openings, groutpressures, water loads, grounddefinitions and references amended

PEM

A3 March2008 All General update. See TMSG paper dated 19 March 2008 for details. PjD onbehalf of TMSG

A4 April2009

All General update. See TMSG paper dated 15 April 2009 for details.

HPE onbehalf of TMSG

A5 April2013

All General update. See TMSG paper dated 18 April 2013 for details

HPE onbehalf of TMSG




NWDSM-Section 4(Contents)-A5 i April 2013

CONTENTS

4.1 INTRODUCTION 4.1/1

4.1.1 General 4.1/1

4.1.2 Definitions 4.1/1

4.1.3 Synopsis 4.1/1

4.1.4 Design Deliverables 4.1/3

4.1.5 Abbreviations 4.1/4

4.2 GENERAL DESIGN CRITERIA 4.2/1

4.2.1 Scope and General Requirements 4.2/1

4.2.2 Design Life, Standards, Codes, and Regulations 4.2/1

4.2.3 Structure Gauge, Headroom and Setting Out 4.2/3

4.2.4 Structure Movements 4.2/4

4.2.5 Hazard on Existing Buildings and Structures 4.2/4

4.2.6 Structure, Ground and Temporary Works Movement Monitoring 4.2/7

4.2.7 Drainage and Flood Protection 4.2/9

4.2.8 Design for Fire 4.2/12

4.2.9 Design for Durability 4.2/12

4.2.10 Water Tightness Control 4.2/17

4.2.11 Void Access and Void Ventilation 4.2/19

4.2.12 Precast Parapet Finishes 4.2/20

4.2.13 Perimeter Fence and Parapet Requirements 4.2/20

4.2.14 Utility and Services Connections 4.2/21

4.2.15 Design For Collision From Railway 4.2/21

4.2.16 Electrical and Mechanical Services Requirements 4.2/22

4.2.17 Specialised Construction Elements 4.2/24

4.2.18 Envisaged Method and Sequence of Construction 4.2/24




NWDSM-Section 4(Contents)-A5 ii April 2013

Figure Number

4.2.9.F1 Stray Current Monitoring Point

4.2.9.F2 Overhead Line Mast - Foundation Details

4.2.9.F3 Corrosion Monitoring

4.2.12.F1 Precast Parapet

4.2.15.F1 Collision Protection – Wall Details

4.2.15.F2 Collision Protection – Pier Details

4.3 SPECIFIC DESIGN CRITERIA 4.3/1

4.3.1 Scope 4.3/1

4.3.2 Cut and Cover Structures 4.3/1

4.3.3 Underground Openings 4.3/2

4.3.4 Immersed Tube Tunnels 4.3/16

4.3.5 Ground Level and Overhead Structures 4.3/23

4.3.6 Structural Movement Joints 4.3/28

Figure Number

4.3.5.F1 Abutment Movement Joint - Access and Details

4.3.6.F1 Structural Movement Joint Details

4.4 DESIGN LOADS 4.4/1

4.4.1 Scope and General Requirements 4.4/1

4.4.2 Combination of Loads and Partial Safety Factors 4.4/1

4.4.3 Dead Loads 4.4/3

4.4.4 Imposed Loads 4.4/4

4.4.5 E&M Loads 4.4/6

4.4.6 Railway Live Loads 4.4/8

4.4.7 Highway Live Loads 4.4/10

4.4.8 Soil and Water Loads 4.4/11

4.4.9 Flotation Loads 4.4/13




NWDSM-Section 4(Contents)-A5 iii April 2013

4.4.10 Wind Loads 4.4/15

4.4.11 Temperature, Shrinkage and Creep Loads 4.4/16

4.4.12 Collision and Impact Loads 4.4/16

4.4.13 Earthquake Loads 4.4/18

4.4.14 Parapet Loads 4.4/20

4.4.15 Crowd Loads 4.4/20

4.4.16 Air Pressure 4.4/21

4.4.17 Construction Loads 4.4/22

Figure Number

4.4.5.F1 Not Used

4.4.5.F2 Not Used

4.4.5.F3 Escalator Hoisting Hooks - Arrangement of Cast-in-Sockets

4.4.6.F1 Nominal Rolling Stock Loading

4.4.6.F2 Derailment Loading Configuration

4.5 SITE INVESTIGATION 4.5/1

4.5.1 Scope 4.5/1

4.5.2 Definitions 4.5/1

4.5.3 General 4.5/2

4.5.4 Extent 4.5/3

4.5.5 Contaminated Land 4.5/3

4.5.6 Pumping Test 4.5/3

4.6 GEOTECHNICAL DESIGN 4.6/1

4.6.1 Scope 4.6/1

4.6.2 Reclamations 4.6/1

4.6.3 Waste Landfills 4.6/2

4.6.4 Slopes and Embankments 4.6/5

4.6.5 Surface Excavation 4.6/6




NWDSM-Section 4(Contents)-A5 iv April 2013

4.6.6 Underground Excavations 4.6/9

4.6.7 Retaining Structures 4.6/10

4.6.8 Foundations 4.6/11

4.6.9 Trackform Substructure 4.6/12

4.6.10 Ground Bolts and Anchors 4.6/14

4.6.11 Blast Design and Vibrations 4.6/16

4.7 INSTRUMENTATION AND MONITORING 4.7/1

4.7.1 Scope 4.7/1

4.7.2 Instrumentation & Monitoring Design 4.7/1

4.7.3 Monitoring 4.7/3

4.8 STRUCTURAL DESIGN 4.8/1

4.8.1 Scope 4.8/1

4.8.2 Dynamic Analysis 4.8/1

4.8.3 Earthquake Analysis 4.8/1

4.8.4 Fatigue Analysis 4.8/4

4.8.5 Design For Flotation 4.8/5

4.8.6 Design for Durability - Steelwork 4.8/7

4.8.7 Design for Durability - Concrete 4.8/8

4.8.8 Prestressed Concrete Structures 4.8/13

4.8.9 Reinforced and Prestressed Concrete Detailing 4.8/14

Figure Number

4.8.9.F1 Column Tie Details for Seismic Design

4.8.9.F2 Ductility Detailing Provision for Seismic Design

4.9 DRAINAGE 4.9/1

4.9.1 Scope 4.9/1

4.9.2 General 4.9/2




NWDSM-Section 4(Contents)-A5 v April 2013

4.9.3 Drainage Water Volume Estimation 4.9/6

4.9.4 Drainage System – Hydraulic Analysis 4.9/8

4.9.5 Station and Ancillary Buildings 4.9/10

4.9.6 Tunnel, Shaft and Cavern Systems 4.9/12

4.9.7 Bridges and Elevated Structures 4.9/13

4.9.8 Building, Line and Portal Sumps 4.9/14

4.9.9 Culverts 4.9/15

4.9.10 Surface Water Groundwater and Foulwater Pumps 4.9/16

4.9.11 Viaducts 4.9/16

Figure Number

4.9.2.F1 Drainage Channel at Diaphragm Wall and Slab Connection

4.9.5.F1 Trackbed Drainage – Stations Base Slab

4.9.5.F2 Trackbed Drainage – Stations Intermediate Slab

4.9.7.F1 Viaduct Drains Emergency Overflow

4.9.8.F1 Drainage – Pump Sump Arrangement

4.9.8.F2 Tunnel Drainage – Sump Pump Arrangement (Sheet 1)

4.9.8.F3 Tunnel Drainage – Sump Pump Arrangement (Sheet 2)

4.10 TEMPORARY WORKS 4.10/1

4.10.1 Scope 4.10/1

4.10.2 General 4.10/1

4.10.3 Design Interfaces with EBS 4.10/2

4.10.4 Design Interfaces with New MTR Structure 4.10/2




4.1 Introduction

NWDSM-Section 4(4.1)-A5 April 2013

4.1/1

4.1 INTRODUCTION

4.1.1 GENERAL

4.1.1.1 All subsections of this Section 4 of the New Works Design Standards Manual(NWDSM) shall be read in conjunction with each other and all other sections of the NWDSM. In some subsections guidance is given with regard to the work tobe undertaken in each stage of the design. However, it shall not be assumed

that the work in previous design stages has been completed or that deliverablesrequired by the NWDSM or Scope of Services Document are available. In thisrespect, reference shall be made to the documents forming the Contract or Agreement for the design of the Works, where any previously produced andavailable documents will be noted.

4.1.2 DEFINITIONS

4.1.2.1 Civil Engineering and Building terms used within this section of the NWDSM arein accordance with BS 6100 “Glossary of Building and Civil Engineering Terms”,unless noted otherwise. Where terms are apparently contradictory or their useis unclear, clarification from the Corporation shall be sought before proceedingwith the design.

4.1.3 SYNOPSIS

4.1.3.1 Section 4 of the NWDSM sets out the design requirements for all underground,surface and above ground civil engineering and building works. It is divided intosubsections as listed below:

i) Subsection 4.2 - General Design Criteria

This subsection defines the general criteria and lists the principal designstandards, codes of practice and government regulations to be used for the design of all civil engineering and building works. It includes theminimum design requirements for the following:

a) surface and groundwater flood protection;b) fire resistant design;c) durability of structures;d) stray current and corrosion;

e) crack control;f) void access;g) precast parapet finishes;h) perimeter fence and parapet;i) utilities and services connections;

j) collision from railway vehicles;k) electrical and mechanical services provisions; andl) construction sequence.




4.1 Introduction


4.1/2

ii) Subsection 4.3 - Specific Design Criteria

This subsection defines additional requirements for the design of specific underground, surface and above-ground structures such as

tunnels, shafts and bridges.

iii) Subsection 4.4 - Design Loads

This subsection defines the particular requirements for loadings to be

used in the design of all civil engineering and building structures.

iv) Subsection 4.5 - Site Investigation

This subsection defines the amount of ground investigation required,

sampling pattern for contaminated land, supervision and data format to

be used in investigations for all civil engineering and building works.

v) Subsection 4.6 - Geotechnical Design

This subsection defines the particular requirements for geotechnicaldesign standards and methods to be used in the design of all civilengineering and building works which include geotechnical processes,slopes and earthworks.

vi) Subsection 4.7 - Instrumentation and Monitoring

This subsection defines the particular requirements for instrumentation

and monitoring of structures and structural movements as well asground and water movements for all civil engineering and building works.

vii) Subsection 4.8 - Structural Design

This subsection defines the minimum requirements for the design,

detailing and analysis of reinforced or prestressed concrete, steelworkand other materials for all civil engineering and building works.

viii) Subsection 4.9 – Drainage

This subsection defines the specific requirements for civil engineeringgroundwater, surface water and foul water drainage systems andconstruction details, including the parameters to be used in the selectionand sizing of surface water pumping systems. It also contains thegeneral requirements for the estimation of surface water flows.

ix) Subsection 4.10 - Temporary Works

This subsection gives general guidance on the design and constructionof temporary works. This subsection is also intended to assist in the

assessment of submissions from contractors for temporary worksdesign.




4.1 Introduction


4.1/3

4.1.4 DESIGN DELIVERABLES

4.1.4.1 The requirements for design deliverables are defined in the Scope of ServicesDocument. These shall be produced during the design process along with the

drawings, calculations and other deliverables required under the particular agreement or contract.

4.1.4.2 The purpose of the sequence of reporting required is to provide sufficientinformation for the design to progress through the design process in a

sequential, logical and controlled manner. This is to ensure that the designdevelopment from the Works conception to completion of construction isadequately undertaken, documented, follows the usual design process andthereby reduces the possibility of unnecessary redesign.

4.1.4.3 Each and every report shall be cross-referenced to the preceding and

corresponding reports where these are available. Reports from previous stagesshall not be assumed to be available unless specifically noted as such by theCorporation before the start of each new design stage.

4.1.4.4 The Scope of Services Document defines the scope of each deliverable andgive the required format and content. It is anticipated that the outline of thereport deliverables will be developed from the given format in the appendices. Allowance shall be made for flexibility of format to meet the specific demands of the Works. For the case of protracted and/or complex Works the report

deliverables may be divided into sections for clarity. Item headings andnumbering shall be developed to suit both the quantity of information availableand the stage of the Works. Where amendments to the requirements are

requested, these shall be approved in writing by the Corporation.




4.1 Introduction


4.1/4

4.1.5 ABBREVIATIONS

AASHTO American Association of State Highway Transport Officials AIP Approval In Principle

CADD Computer Aided Design and DraftingCPF Controlled Permeability FormworkCSF Condensed Silica FumeDES Design StatementDSD Drainage Services Department

DFT Dry Film ThicknessE&M Electrical and MechanicalEBS Existing Buildings and StructuresECS Environmental Control SystemEPB Earth Pressure Balancing

EPD Environmental Protection Department

FOS Factor of SafetyFRP Fire Resistance PeriodGGBS Ground Granulated Blast furnace SlagGEO Geotechnical Engineering Office

HAT Highest Astronomical TideHKPWDM Hong Kong Port Works Design ManualHKSDM Hong Kong Structures Design ManualHKSWDM Hong Kong Stormwater Drainage ManualIMT Immersed Tube Tunnel

M&W Materials and WorkmanshipNATM New Austrian Tunnelling MethodNDL Net Downward Load

NSF Negative Skin FrictionNWDSM New Works Design Standards Manual

OHL Over Head LinePIP Packed-in-place PilesRMJ Rail Movement JointRPM Railway Protection Manual

SCLM Sprayed Concrete Lining MethodSCR Station Control RoomSGI Spheroidal Graphite Cast IronSLS Serviceability Limit StateSMJ Structural Movement Joint

SPC Seismic Performance CategoryTBM Tunnel Boring MachineTE Tunnel ElementULS Ultimate Limit StateWSD Water Supplies Department




4.2 General Design Criteria


4.2/1

4.2 GENERAL DESIGN CRITERIA

4.2.1 SCOPE AND GENERAL REQUIREMENTS

Scope

4.2.1.1 This subsection defines the general design criteria and the principal designstandards, codes of practice, and government regulations to be used for thedesign of all civil engineering works and building works.

4.2.2 DESIGN LIFE, STANDARDS, CODES, AND REGULATIONS

General

4.2.2.1 The design life and principal standards given in this subsection and theFunctional Requirements Manual shall be complied with, except where theseare amended by other clauses or in specific written instructions from the

Corporation.

4.2.2.2 The Corporation may direct that different or further criteria be adopted inadditional to those laid down in this subsection, or other documents it refers to,at its discretion. However, the clauses, or other documents it refer to, may not

be modified or waived without the prior written approval of the Corporation.

4.2.2.3 Any reference to a Standard, Code of Practice or Manual shall be the latest

issue thereof including all amendments, unless noted otherwise.

Design Life

4.2.2.4 In the design of structures for loadings, durability, and safety within a givenreturn period, the design life shall be taken as 120 years for all structures. In

the design for durability of all structures reliance shall not be placed solely onthe recommendations of International Standards. In selecting materials andtaking measures for durability due account shall be taken of the generallyaggressive environment in which the Corporation's structures are placed. Dueconsideration shall be given to the monitoring and maintenance works required

to maximise the life of the structure.

4.2.2.5 Where elements of the structures are to be maintained and/or are replaceablewithin the overall design life of the structure, the design shall include provisionfor ease of inspection, maintenance and replacement during ‘non-traffic hours’.

These hours are generally from 0100 hrs to 0500 hrs on any day, exceptseveral “special days” during the course of a year in which 24-hour train serviceis required. Such maintenance or replaceable elements shall be minimisedproviding that the life cycle cost of the structure is also minimised.






4.2/2

Hong Kong Standards and Regulations

4.2.2.6 In certain cases the design shall comply with Hong Kong GovernmentRegulations, Standards or Ordinances in addition to the requirements of this

NWDSM.

4.2.2.7 For structures subject to the requirements of the Buildings Ordinance andBuilding Regulations, the most onerous structural design requirements of theBuildings Ordinance, the Building Regulations or the provisions of the NWDSMshall apply.

Principal Design Standards, Codes, and Regulations

4.2.2.8 Underground structures, shall be designed in accordance with “Hong Kong

Code of Practice for the Structural Use of Concrete”, and, BS EN 1992-3: Liquidretaining and containment structures.

4.2.2.9 Bridges shall be designed in accordance with BS 5400: “Steel, Concrete andComposite Bridges” and the Hong Kong Structures Design Manual (HKSDM).

4.2.2.10 Surface and above ground structures, other than bridges, shall be designed inaccordance with “Hong Kong Code of Practice for the Structural Use of Concrete”.

4.2.2.11 Structural Steel within Stations, Depots and Ancillary Buildings shall bedesigned in accordance with “Hong Kong Code of Practice for the StructuralUse of Steel”.

4.2.2.12 Foundations shall comply with “Hong Kong Code of Practice for Foundations”,.Limit state philosophy, using BS 5400, “Hong Kong Code of Practice for theStructural Use of Steel” or “Hong Kong Code of Practice for the Structural Useof Concrete” as appropriate, may be used for the design of the foundationstructures.

4.2.2.13 The design of highway and pedestrian structures, including parapets andassociated pedestrian ways (other than those supported by structures),miscellaneous road works, traffic signs, and road markings shall be inaccordance with the relevant sections of the HKSDM.

4.2.2.14 The design of seawalls associated with reclamation and miscellaneous marineworks shall be in accordance with relevant sections of the Hong Kong PortWorks Design Manual (HKPWDM).

4.2.2.15 The design of geotechnical works, which support or are adjacent to railwaystructures, such as embankments or cuttings and the like, shall be inaccordance with the various references given in the NWDSM and relevant GEOGuides published by Geotechnical Engineering Office (GEO).

4.2.2.16 Drainage of surface water and foul water shall be designed in accordance withthe NWDSM and the following codes and regulations as appropriate:






4.2/3

i) BS EN 752: “Drain and Sewer Systems Outside Buildings” Parts 1 to 4(successor to BS 8005: “Sewerage”);

ii) Hong Kong Buildings Ordinance and Building Regulations;

iii) Hong Kong Government Drainage Services Department’s Stormwater Drainage Manual (HKSWDM) and Sewerage Manual;

iv) PNAP183: “Keeping Buried Services out of Slopes”;

v) Hong Kong Code of Practice on Inspection and Maintenance of Water Carrying Services Affecting Slopes; and

vi) Environmental Protection Department (EPD) requirements.

4.2.2.17 In certain circumstances, the recommendations of other internationally

recognised design standards and codes of practice may be adopted with theprior written approval from the Corporation.

4.2.2.18 Due cognisance shall be taken of the requirements of the Corporation’s RailwayProtection Manual (RPM) when constructing works adjacent to the existing MTRrailway system.

4.2.2.19 The Designer is expected to be fully conversant with all proposal/contract

documents and other sections of the NWDSM. The Designer shall be requiredto reflect the intentions of these documents in the design, but shall also drawthe Corporation's attention to any special conditions or developments which

may require modification of these documents. Where requirements areduplicated and are required to be applied, the more onerous shall be adopted.

4.2.3 STRUCTURE GAUGE, HEADROOM AND SETTING OUT

4.2.3.1 All structures, permanent or temporary, adjacent to the track shall be designed

and constructed such that no part of any structure, cladding or finish shall at anytime under any condition of loading, settlement or creep, encroach within thestructure or construction gauge as defined in Section 3 of the NWDSM.

4.2.3.2 Apart from the general clearances to areas adjacent to track, the provision for

minimum headroom shall be in accordance with Section 5 of the NWDSM for stations and ancillary buildings; Section 3 of the NWDSM for bridges over railways and HKSDM for any other bridge, viaduct or elevated structure. Allowance shall be made for foundation movement, shrinkage and creep, where

appropriate, in the determination of minimum headroom.

4.2.3.3 Railway structures shall be set out relative to the railway alignment. Fullaccount of the constraints imposed by the railway alignment shall be allowed for in designs. Any change to the proposed setting out of a railway structure shall

be cross-referenced to the alignment and shall be submitted for the approval of the Corporation before implementation. Due allowance shall be made in the

setting out details and design for the movement of the works during the






4.2/4

operational stage and that may occur during the construction of the works.

4.2.4 STRUCTURE MOVEMENTS

General

4.2.4.1 The design shall include an assessment of movements induced by the workson Existing Building and Structures (EBS), new Permanent Works and

Temporary Works movements. Recommendations from the movementassessment shall be incorporated into the Tender and Contract documents.

Railway Structure Movements

4.2.4.2 The adopted designs and construction methods shall limit new PermanentWorks structure movements to less than those specified in the RPM after

commencement of trackform installation in new railway structures, or at anytime in existing railway structures.

Other Structure Movements

4.2.4.3 Detailed assessments shall be carried out on EBS based on the availablerecords so as to evaluate the structural implications and required movement /

distortion limits from the proposed Works.

Differential Settlements

4.2.4.4 The general requirement for differential settlement analysis shall be taken intoconsideration in the structural design calculations and details for all structures.This is particularly important where restrictions in ground support systems andground parameters can lead to large changes in support stiffness.

4.2.5 HAZARD ON EXISTING BUILDINGS AND STRUCTURES

General

4.2.5.1 All Corporation structures, particularly underground structures, shall bedesigned so that they can be constructed in a practical manner which

minimises any ground movements arising from construction works which areliable to cause damage to any EBS, slopes and utilities. In order todemonstrate that this is the case, ground movements shall be estimated using

methods which have been approved in principle by the Corporation and thelikely effects on structures reported in the EBS reports defined in the Scope of Services Document or Contract documents. Ground movement shall meanmovement or distortion of the ground in any direction, subsidence or collapse.

4.2.5.2 Although the following clauses are specifically for EBS, a similar procedureshall be used for identifying the risks of damage to all other civil engineeringworks and features which may be sensitive to ground movements such as

slopes, retaining walls, services, utilities, drainage, pavements and street






4.2/5

furniture and reported in a similar manner to that required for EBS.

4.2.5.3 Each design stage will require an increased level of detail to reflect thedevelopment of the project with the aim of eliminating from further consideration:

i) those EBS which fall into a damage assessment category which are of acceptably low risk;

ii) those EBS which fall into a damage assessment category which isconsidered to be totally unacceptable such that the design or method of

construction must be changed.

4.2.5.4 The design of Permanent Works and Temporary Works shall ensure that thedegree of damage to EBS falls within the limits set in Risk Category 0, 1 or 2 of the Building and Structure Damage Classifications given in Table 4.2.5.T1.

The empirical nature of the classification should be noted.

Buildings should be reviewed to ensure that the theory is applicable, and the

application of the classification made primarily with respect to the ease of repair.






4.2/6

Table 4.2.5.T1 Building and Structure Risk Categories

Building and Structure Damage Classification

(after Burland et al (1977) and Boscardin and Cording (1989)

Approximately

Equivalent Ground

Settlements andSlopes

(after Rankin (1987))

Risk

Category

Description

of Degree

of Damage

Description of Typical

Damage and Likely Forms of

Repair for Typical Masonry

Buildings

Approx

Crack

Width

(mm)

Max.

Tensile

Strain

(%)

Max.

Slope

of

Ground

Maximum

Settlement

of

Building

(mm)

0 Negligible Hairline cracks Less than

0.05

1 Very Slight Fine cracks easily treated during

normal redecoration. Perhaps

isolated slight fracture in building.

Cracks in exterior brickwork visible

upon close inspection.

0.1 to 1 0.05 to

0.075

Less

than

1:500

Less than

10

2 Slight Cracks easily filled. Redecoration

probably required. Several slight

fractures inside building. Exterior

cracks visible: some repointing

may be required for weather-

tightness. Doors and windows

may stick slightly.

1 to 5 0.075 to

0.15

1:500 to

1:200

10 to 50

3 Moderate Cracks may require cutting out and

patching. Recurrent cracks can be

masked by suitable linings. Re-

pointing and possibly replacement

of a small amount of exterior

brickwork may be required. Doors

and windows sticking. Utility

services may be interrupted.

Weather-tightness often impaired.

5 to 15 or

a number

of cracks

greater

than 3

0.15 to

0.3

1:200 to

1:50

50 to 75

4 Severe Extensive repair involving removal

and replacement of sections of

walls, especially over doors and

windows required. Windows and

frames distorted. Floor slopes

noticeably. Walls lean or bulge

noticeably, some loss of bearing in

beams. Utility services disrupted.

15 to 25

but also

depends

on number

of cracks

Greater

than 0.3

1:200 to

1:50

Greater than

75

5 Very Severe Major repair required involving

partial or compete reconstruction.

Beams lose bearing, walls lean

badly and require shoring.

Windows broken by distortion.

Danger of instability.

Greater

than 25

but also

depends

on number

of cracks

Greater

than 1:50

Greater than

75






4.2/7

Table 4.2.5.T1 Building and Structure Risk Categories (Continued)

Notes: 1) The table is based on the work of Burland et al (1977) and includestypical maximum tensile strains for the various damage categories

(column 5) used in the Building and Structure Classification.

2) Crack width is only one aspect of damage and should not be used on itsown as a direct measure of it.

3) Columns 6 and 7 also indicate the 'green-field' settlements and

settlement trough slopes and are based on the methods of Rankin(1987). Risk Categories using the Rankin method areapproximately equivalent to those proposed by Burland, although insome cases there may be significant differences.

EBS Condition And Structural Surveys

4.2.5.5 The Corporation will arrange for a detailed condition survey to be carried out byan independent surveyor on all EBS in Risk Category 1 to 5 inclusive, primarily

for insurance purposes. However, a review by the Designer of these surveysshall be carried out and advice be given on the implications/considerations, if any, with respect to the proposed construction options and designs, if differentto those contained within the detailed evaluations carried out previously.

4.2.5.6 The Corporation will arrange for a condition survey to be carried out for EBSadjacent to the work sites. Generally, EBS subject to at least 10mm groundmovement or induced vibrations of 13mm/s will be surveyed, but exceptional

buildings and structures outside such zone of influence should be consideredon their merits.

4.2.6 STRUCTURE, GROUND AND TEMPORARY WORKS MOVEMENTMONITORING

4.2.6.1 Materials and Workmanship (M&W) Specification requires movements of allmajor temporary works including cofferdams, excavations and adjacent EBS asspecified in the Contract to be monitored within and adjacent to the Worksduring the Contract period. Therefore Temporary Works, new Permanent

Works, ground areas and EBS adjacent to new Permanent Works equivalent to

or defined as Category 2 to 5 shall be defined as requiring monitoring (hereafter referred to as 'monitored elements') in the Design and Tender or Contractdocuments as appropriate.

4.2.6.2 In accordance with the M&W Specification the Contractor is also required toestablish survey reference points on both sides of the front and back, top andbottom of adjacent EBS forming at least 8 reference points per buildingidentified as requiring monitoring. Readings of all monitoring points at regular

(at least weekly) intervals are required to be taken and submitted to theCorporation promptly throughout the duration of the Contract. However where itis considered that the building sensitivity or the predicted rate of movement

warrants more stringent requirements, the extent of monitoring and frequency






4.2/8

shall be subject to the approval of the Corporation and specified in the Designand Tender or Contract documents as appropriate.

4.2.6.3 The frequency and extent of monitoring for monitored elements shall be defined

and shall be in all cases sufficient to give a comprehensive picture of overallmovements. Measures shall be subject to the approval of the Corporation.

4.2.6.4 Structure, ground and Temporary Works movement monitoring drawings shallbe produced for both the Tender and Contract documentation. The drawingsshall incorporate the various movement control levels and requirements of the

M&W Specification. These drawings will form the basis for monitoring anddefine the minimum requirements that the Contractor shall undertake.

4.2.6.5 Movement control levels for the monitored elements shall be defined inaccordance with the following criteria.

i) Alert Level - Remedial measures agreed.

ii) Alarm Level - Remedial measures instituted and revised Alert

and Alarm levels set.

iii) Action Level - Serviceability limit, stop work.

4.2.6.6 " Alert Level" shall initially be set as 0.5 times the serviceability limit movementfor the monitored elements. The serviceability limit movement for a monitoredelement shall be the lesser of:

i) the calculated design value for the serviceability limit movement for theTemporary Works element;

ii) the Temporary Works element movement which would theoreticallycause services disruption, RPM, Buildings Ordinance (BO), EBS

allowable structure or ground limits as defined in Cl.4.2.5.4 and Table4.2.5.T1 to be compromised; and

iii) allowable movement of the monitored element in accordance with RPM,

BO, EBS or ground limits as defined in Subsection 4.2.5 and Table4.2.5.T1.

4.2.6.7 The M&W Specification requires that following "Alert Level" movement at anylocation the Contractor shall immediately submit a written report to the

Corporation reviewing all total and differential movements/distortions to date,assessing the effects of the movements/distortions on monitored elements andpredicting further movements and their effect on monitored elements based onthe trend to date. Where it is considered and agreed by the Engineer thatmovement trends indicate that "Alarm Level" may be reached during the course

of the Works, the Contractor is required to submit proposals for remedialmeasures to limit further movement for the approval of the Engineer. Theremedial proposals shall be reviewed and the Engineer advised as to their likelyefficacy. Notwithstanding the above a change between consecutive readings

greater than 5mm shall necessitate the imposition of "Alert Level" status






4.2/9

regardless of the global movements.

4.2.6.8 " Alarm Level" shall be set at 0.7 times the serviceability limit movement for the

monitored element. In accordance with the M&W Specification "Alarm Level" of

movement at any location requires the Contractor to immediately instigate theapproved remedial measures in accordance with the Contractor's method of construction and Temporary Works, agreed at the "Alert Level" status. Work

may then only proceed if the remedial measures have been implemented andare in the opinion of the Engineer shown to be effective.

4.2.6.9 Upon reaching "Alarm Level' status the Contractor is required by the M&WSpecification to submit an updated report reviewing the movements including

differential movements and distortion. The report shall assess the effects onmonitored elements and predict further movement and their subsequent effecton monitored elements. In addition, revised "Alert Level" and "Alarm Level"values which take into account the implemented remedial works shall be

submitted and approved by the Engineer before work may continue.

4.2.6.10 " Action Level" shall initially be set at the serviceability limit movement for the

monitored element. In accordance with the M&W Specification movementgreater than the "Action Level" at any location will, subject to agreement by TheEngineer, necessitate an immediate cessation to work. Requirements for building resumption, resumption of construction and a complete review of theTemporary Works and construction methods will be required as instructed by

the Engineer.

4.2.6.11 Upon reaching "Action Level" status in accordance with the M&W Specification

the Contractor will be required to provide a report detailing the full history of movements and remedial measures adopted in relation to the actual

construction sequence. The report shall contain a review and interpretation of the events and give recommendations for enabling the work to proceed. Workmay only resume upon the written instruction of the Engineer.

4.2.7 DRAINAGE AND FLOOD PROTECTION

Flood Protection to Structures

4.2.7.1 All openings into underground or surface structures shall be located

above the 1 in 200 year flood level. The effects of burst water mains andblocked surface water drainage systems shall be included in thedetermination of the design flood level. An analysis of the flood paths for thearea surrounding the structures shall be carried out in order to determine the

appropriate design flood level. In general, structures located on flat land shallhave a minimum flood protection of 1.2 m above the surrounding ground levelor natural ground water level. Flood protection requirements for structureslocated on slopes shall be assessed individually.

4.2.7.2 Structure entrances shall be protected by a combination of steps or slopes asappropriate up to a landing of at least 450 mm above street level, combined

with removable flood boards to provide the remaining minimum margin to the






4.2/10

design flood level. Standard flood board and the associated cast in fixingdetails are given in Section 5 of the NWDSM.

4.2.7.3 Entrances to underground structures shall be protected by flood doors

designed to withstand the full head of water to the design flood level. Suchdoors shall be designed to be operated manually by a maximum of twopersons.

4.2.7.4 Vehicle ramps into underground structures shall have a crest at or above thedesign flood level. A separate drainage system leading to the structure

drainage system shall be provided on the structure side of the crest.

4.2.7.5 All civil engineering and building works shall be provided with drainagesystems designed to cope with water from all sources such as rainfall,seawater overtopping, broken services, nominal seepage through

underground structures and track wash down water in accordance with

Subsection 4.9.

Flood Protection for At-Grade Tracks

4.2.7.6 At grade tracks shall be protected against groundwater flooding by raising therailway formation (underside of sub-ballast) to above the 1 in 200 year floodlevel. Where the railway formation is unavoidably below this level or wherethe sub grade softening or movement may otherwise occur then, sumps,

pumps, and subsurface drainage system shall be provided to prevent water levels rising exceeding 1 meter below the formation level.

4.2.7.7 Notwithstanding the above, a drainage system shall be incorporated into thedesign for draining surface water.

Flood Protection Adjacent to Seawalls

4.2.7.8 The location of the 'Railway Boundary' and the necessity for protection

against seawall overtopping shall be agreed with the Corporation at the startof the design process.

4.2.7.9 Where the Railway Boundary may be affected by seawall overtopping water,measures shall be adopted to ensure the following are complied with:

i) emergency personnel/detraining and accessing to/from the landwardside of the Railway Boundary during storm events shall be providedwhere possible. Where this is not possible, overtopping protectionshall be provided to the emergency access path, as defined in (iii) below, on the seaward side to the same degree as required within theRailway Boundary, as given in Cl.4.2.7.11;

ii) no maintenance access shall be allowed during storm events from the

seaward side of the Railway Boundary; and

iii) a paved promenade/maintenance path with a minimum width of 4 m

(or up to the Railway Boundary, whichever is less), shall be provided






4.2/11

at the back of the seawall.

4.2.7.10 If any of the requirements of Cl.4.2.7.9 cannot be complied with, morestringent criteria than those given in Cl.4.2.7.11 may be required and specific

approval from the Corporation shall be obtained. Reference should also bemade to Cl.4.9.2 for the provision of drainage inside the Railway Boundary.

4.2.7.11 Measures shall be adopted to ensure the following limitations on wave andwind driven overtopping water volumes are complied with:

i) Operational limit (no damage)Up to 1 in 10 year event return periods:Railway Boundary average overtopping limit ≤ 0.001l/s/m.

ii) Normal storm (limited damage)

1 in 10 year to 1 in 100 year event return periods:

Railway Boundary average overtopping limit ≤ 0.02 l/s/m.

iii) Extreme storm (significant damage)

1 in 100 year to 1 in 200 year event return periods:Seawall Crest average overtopping limit ≤ 200 l/s/m.

4.2.7.12 The terms and values given above have been determined from the guidancegiven in CIRIA Special Publication 83, Manual on the Use of Rock in Coastal

and Shoreline Engineering.

4.2.7.13 When designing sensitive / fragile components within the Railway Boundary, it

should be noted that instantaneous overtopping rates over a single waveperiod can be 500 to 1000 times average rates (derived over a period of 100

to 1000 waves) given in Cl.4.2.7.11.

4.2.7.14 Areas of the Railway shall be identified which may be particularly sensitive tothe risks of overtopping for reasons of :

i) coastline geography and seabed hydrography;

ii) seawall structural form; and

iii) transitions between structures and the like.

4.2.7.15 The Corporation shall identify similar particularly sensitive locations due toprovision of :

i) E&M equipment, which is more sensitive than usual;

ii) sensitive operational requirements; and

iii) sensitive maintenance requirements.

4.2.7.16 The probability of inundation in the areas noted in Cl.4.2.7.14 and Cl.4.2.7.15

and the desirability for more stringent mitigation measures than those stated






4.2/12

in Cl.4.2.7.11 shall be identified. The provision of any mitigation measuresshall be agreed with the Corporation for each situation.

4.2.8 DESIGN FOR FIRE

4.2.8.1 All structures shall be designed to satisfy the fire safety requirements asspecified in Section 5 of the NWDSM.

4.2.8.2 Materials specified for the Works shall be non-combustible and do not emittoxic fumes when subject to heat or fire, except where specifically allowedwithin the NWDSM, for example pipework. In all cases where there is asignificant fire risk, materials shall be self-extinguishing, low flammability, low

smoke and low toxicity type.

4.2.8.3 The detailing of structural elements shall be in accordance with “Hong Kong

Code of Practice for the Structural Use of Concrete” to achieve the FireResistance Periods specified in Section 5 of the NWDSM, or those requiredunder the Buildings Ordinance, whichever is more onerous.

4.2.8.4 The minimum thickness of reinforced concrete walls or slabs separatingrailway structures from structures owned or controlled by any other party shall

be 200 mm.

4.2.8.5 Fire protection steel mesh is required within the nominal concrete cover zonefor the concrete cover greater than 40mm according to the Code of Practicefor Fire Safety in Buildings. The fire protection steel mesh shall be either hot

dipped galvanised steel or stainless steel. However, fire protection steelmesh shall not be used in the soffit of tunnel lining above running tunnels towhich there is no access during traffic hours. In this case the risks to trainoperation of spalling concrete due to mesh corrosion are considered morelikely to occur than fire damage.

4.2.8.6 With respect to the condition as stated in CI.4.2.8.5 where fire protection steelmesh shall not be used, to prevent the threat of concrete spalling during atunnel fire, a passive fire protection system by the addition of monofilamentpolypropylene fibres (PPF) in the concrete shall be provided in lieu of the

required fire protection steel mesh. PPF shall be complied with therequirements of BS EN 14889-2:2006.

4.2.8.7 Acceptance for the use of PPF including material properties and concrete mixshall be obtained from the Corporation and relevant government authorities.

4.2.9 DESIGN FOR DURABILITY

General

4.2.9.1 Particular care should be taken to ensure that:

i) designs and details are capable of being executed to the required






4.2/13

standard, with due allowance for dimensional tolerances and thecapabilities of the workforce;

ii) there are clear instructions on permissible deviations; and

iii) elements which are critical to workmanship, structural performance,durability, and appearance are clearly identified on the drawings.

4.2.9.2 In carrying out structural designs, the Designer shall ensure that both theultimate and serviceability limit-states have been checked in accordance with

the NWDSM and other adopted relevant standards and codes of practices.

Soil and Groundwater Conditions

4.2.9.3 The Designer shall take full account of the prevailing soil and groundwater conditions and those predicted to occur within the design life of the Works, in

designing to achieve durability.

4.2.9.4 Table 4.2.9.T1 gives indicative values from which the Designer can assess

the degree of severity of soil and groundwater conditions.

Table 4.2.9.T1 Soil and Groundwater Criteria

SOIL GROUNDWATER

Chloride

(Cl)

Sulphate

(SO4)

pH Resistivity

Ohm/cm

Chloride

(CI)

Sulphate

(SO4)

pH Resistivity

Ohm/cm

NON

AGGRESSIVE

Soil or

groundwater must satisfy all

criteria

⟨0.05% ⟨0.24% ⟩5.5 ⟩10 000 ⟨200 ppm ⟨0.4 g/L ⟩5.5

⟩10 000

AGGRESSIVE

Soil or

groundwater

exceeding any

limit

⟩0.05% ⟩0.24% ⟨5.5 ⟨10 000 ⟩200 ppm ⟩0.4 g/L ⟨5.5

⟨10 000

Notes: 1) Sites with low pH or where sulphate reducing bacteria or

industrial pollutants occur require special consideration.

2) This table should not be confused with the ground conditions

for earthing mat design where high resistivity (>10,000Ohm/cm) implies ‘aggressive’ conditions requiring a larger earthing mat and a low resistivity implies ‘non aggressive’conditions (<10,000 Ohm/cm) or a smaller earthing mat.

4.2.9.5 Where 'Aggressive' conditions are determined, a statement describing themethods proposed to be adopted to enable the structures to achieve thespecified design life shall be submitted. Account shall also be taken of theenvironmental exposure conditions of the structure when designing for durability. For example, the inside face of a tunnel wall or lining which is

exposed to constant wetting and drying is more at risk of attack than theoutside of the lining which is permanently in contact with the groundwater in

areas where oxygen will not be present.






4.2/14

Sulphates

4.2.9.6 In general Hong Kong soils contain negligible amounts of naturally occurring

sulphate. However, if the results of the sulphate tests carried out during thesite investigation indicate that attack on the cement in the concrete is likely tooccur, appropriate preventive measures shall be taken. In areas of reclamation; other marine environments; leaking salt water mains and/or service reservoirs particular attention shall be paid to the presence of water borne sulphates.

Chlorides

4.2.9.7 Full account of the prevailing chloride concentrations in soil and groundwater

at each location shall be taken in the selection of concrete class, cover anddesign crack width and the necessity for external waterproof membranes and

coatings.

4.2.9.8 Particular attention shall be paid to the detailing of underground structures

and their joints, where capillary rise and rapid drying conditions created bytrain-induced air movements lead quickly to an accumulation of chlorides fromany groundwater even with relatively low salt concentrations.

Acidity

4.2.9.9 Although the acidity of Hong Kong soils is generally low, the Corporation'sattention shall be drawn to situations where pollution or other contaminants

are likely to have altered the acidity of the soil.

Addi tional Durabil ity Measures

4.2.9.10 In structural elements subject to aggressive water wetting and drying,aggressive water spray or other aggressive environments, conditions will be

such that adequate durability cannot be achieved through use of themeasures defined in Subsection 4.8. A range of secondary measures toimprove durability is available and should be considered in specific locations.Examples of these secondary measures are:

i) controlled permeability formwork (CPF);

ii) epoxy-coated, stainless steel or galvanized reinforcement bars;

iii) moderate heat cement which conforms to BS 1370: “Specification for Low Heat Portland Cement”;

iv) water repellent surface penetrants such as Silane;

v) surface coatings or membranes such as epoxy paint or polymer-modified cementitious coatings;

vi) Installed impressed or sacrificial cathodic protection;






4.2/15

vii) hydrophobic pore-blocking/lining additives to concrete;

viii) use of 37.5 mm aggregate for very large structural elements where

limitation of temperature rise in the interior is important. Suchconcrete normally contains a higher volume fraction of aggregate thanconcrete made with 20 mm maximum size aggregate and, as a result,would offer advantages in lower w/c ratio for the same workability,lower creep and shrinkage, higher elastic modulus, and lower cementitious content and have lower heat evolution;

ix) Condensed Silica Fume (CSF) or Ground Granulated Blast furnaceSlag (GGBS); and

x) waterproof membranes and protective coatings.

4.2.9.11 The specification of any secondary measures must not be taken as justification for a relaxation of the primary requirements for durability.

4.2.9.12 Where secondary measures are proposed a detailed justification shall begiven and the approval of the Corporation obtained for their incorporation intothe Works. A revised materials and workmanship or performancespecification which takes the secondary measure(s) into account shall also beprovided.

Stray Current Collection System, Monitoring System and MitigationMeasures

4.2.9.13 A Stray Current Collection System, i.e. stray current collection steel mesh,

shall be provided in the trackform to minimise the leaking of traction returncurrents from the rail into adjacent reinforced structures. The effectiveness of the stray current collection steel mesh depends on the continuity betweenmeshes.

4.2.9.14 In addition, a Stray Current Monitoring System shall be provided in thesupporting structures to measure the effectiveness of the stray currentcollection steel mesh and detect any build up of local 'hotspots' of currentdensity in the reinforced structures during the train operation. The E&M

design requirements are contained in Section 7 of the NWDSM. An example

of a stray current monitoring point is shown in Fig 4.2.9. F1.

4.2.9.15 Several civil provisions for the Stray Current Monitoring System such assuperstructure isolation, rebar bonding and terminal point shall be provided.

The reinforcement cage of both underground structure external envelope andbridge superstructures shall be isolated from earth; prestressing strand; steelcast-in plates or other steel elements so that the reinforcement cagemaintains a high resistance to earth and other electrically conductiveelements.

4.2.9.16 Bridge structures shall be electrically isolated from their supports. Particular

attention shall be paid to ensure that mechanical bearings have dedicated






4.2/16

insulated layers and that no ancillary metalwork, such as joint covers or drainage pipes, compromise this isolation. In addition, prestressing systemsshall be electrically isolated from concrete and reinforcement using isolatingwashers, plastic sheathing, plastic trumpets and plastic coupler covers to

further protect these critical systems from stray currents. Further details andrequirements of prestressing system are given in Subsection 4.3.

4.2.9.17 Overhead line mast concrete supports shall be detailed so that the holdingdown bolts are electrically isolated from reinforcement within the support. SeeFig 4.2.9.F2.

4.2.9.18 Continuity bars shall be provided in one longitudinal direction at approximately6m centres on inside faces around sections by welding bars at laps. At everysecond longitudinal lap location, one inside and outside face transversecontinuity bar shall be welded to the longitudinal continuity bars at transverse

laps. For both transverse and longitudinal laps welding shall be carried out at

two separate locations along the lap at least 500mm apart, the cross-sectionof the weld at the weld throat shall not be less than twice the area of thesmaller bar being welded to ensure that the electrical resistance of the

connection is equivalent or less than the parent bar.

4.2.9.19 For bridge substructures such as piers and abutments, two transversecontinuity bars shall be provided at link / horizontal bar and at approximately500 mm above finish ground level as described in Cl.4.2.9.18. These link /

horizontal bar shall both be welded to two vertical continuity reinforcing bar,also welded at laps.

4.2.9.20 For tunnels where precast concrete segmental linings are proposed, therequirements of stray current control and monitoring shall be discussed with

and agreed by the Corporation.

Enablement Works for Cathodic Protection

4.2.9.21 To enable the future installation of a cathodic protection system, the terminal

points, similar details as a stray current monitoring point, shall be provided ineach pier and at 21m maximum centres along the alignment in each room,cell or trackside of underground structures as appropriate. Refer to Fig.4.2.9.F1 for details.

Corrosion Monitoring System

4.2.9.22 In addition to general monitoring by normal visual checks, half cell checks,concrete samples and the like, the installation of corrosion monitoring systems

shall be considered where they will provide useful data and can be readilymaintained.

Examples are the joint of a station box to a tunnel, or adjacent to joints inunderground structures where aggressive conditions are known to exist.

4.2.9.23 Cables from components shall be terminated in the surface mounted

termination box at each location to enable local manual reading of corrosion






4.2/17

monitoring data. The system shall be designed and supplied by theSystemwide E&M Contractor. A typical arrangement is shown in Fig 4.2.9.F3.The cast-in items shall be installed by the Civil Contractor and incorporated inthe design and Tender or Contract documents as appropriate.

4.2.10 WATER TIGHTNESS CONTROL

General

4.2.10.1 The following requirements of water tightness control shall be applied to allstructural elements as defined in Table 4.2.10.T1 and Table 4.2.10.T2.

Table 4.2.10.T1 Water Tightness Control Applications

Structu ral Element Class

- Roof slabs for stations, entrances, ancillary buildings and reinforced cast

in situ tunnels

- Suspended slabs over tracks, concourses, car parks, and any other

similar sensitive zones which are subject to wash down, train air

conditioning condensate, leakage, or rain water

- Buried or submerged perimeter walls to which finishes are applied on the

interior

I

- In situ building and tunnel base slabs

- In situ external and internal walls with no finishes

- In situ abutments and retaining walls

- Unreinforced in situ or reinforced segmentally lined tunnels or shafts

II

- Diaphragm walls, secant or contiguous piled walls. III

Table 4.2.10.T2 Water Tightness Control Requi rements

Class Description

I Free from all visible leakage, seepage, and damp patches.

II Leakage shall be restricted to minor damp patches with no visible flow of water.

III Leakage shall be restricted to damp patches on the face of the concrete, at

horizontal construction joints and to minor weeping of vertical construction joints in walls.

Jetting of water will not be acceptable.

The total inflow over a given area of structure shall not exceed 0.12 l/m² per

day overall and 0.24 l/day on any separate square metre.

Note: 1) For the purposes of this table, ‘damp’ shall be defined as wet with no visible film of water.

4.2.10.2 If it is considered that a relaxation may be warranted, taking all factors including

initial and recurrent costs into account, a full justification shall be submitted for the approval of the Corporation before proceeding with the detailed design.






4.2/18

4.2.10.3 In selecting an alternative class of water tightness control for a structuralelement, account shall be taken of; the ground and groundwater conditions; thelikely construction method; the structural element form and the function of theroom / area adjacent.

Minimum Requirements for Structures

4.2.10.4 For the underground structures, the waterproof membrane shall be taken to 225mm above ground level.

4.2.10.5 All movement joints shall include a heavy duty water bar and the movement gapshall be filled and sealed with an Approved non-rotting filler material and internalsealant. Particular attention shall be paid to the joint between station entrancesand the station box and piled structure to non-piled structure interfaces where

relative movement can occur.

Class I Structural Element Requirements

4.2.10.6 Special care shall be taken in the design and detailing to ensure a

homogeneous dense concrete. In addition the following specific provisionsshall apply :

i) an external waterproof membrane shall be provided for the structural

element. The membrane shall be protected by a 75mm thick screed of Class 20/20 concrete on horizontal or sloping upper faces and byproprietary protection boards or block work on vertical faces; and

ii) construction joints shall have a water bar or hydrophilic waterproofingstrip or resin injection tube as appropriate and shall be sealed on theinternal face.

Class II Structural Element Requirements

4.2.10.7 Design, detailing and specific provisions shall be as for Class I elements exceptthat internal joint sealant is not required.

Class III Structural Element Requirements

4.2.10.8 Class I requirements shall apply except that water bars, waterproof membranes

and sealant shall be provided only where the particular circumstances demandit.

Waterproofing Membranes and Surface Falls

4.2.10.9 All cast underground structures that are required to be watertight, water retaining or water excluding, except bored tunnels with precast concrete

segmental linings, shall have an external waterproofing membrane consisting of a two coat, high quality, spray applied elastomeric, jointless system, at least 2mm thick, unless otherwise approved by the Corporation. The waterproof membrane shall be applied directly to the concrete substrate before the laying

of any screed.






4.2/19

Alternatively, performed sheet membrane, not less than 2 mm thick, may beproposed when all factors such as excavation depth, hydrostatic pressure,working space, risk and consequences of damage during construction,

access for repair etc are considered. Particular attention shall be given topreparation of the substrate.

4.2.10.10 Waterproof membranes for building or tunnel base slabs shall be provided witha robust, preformed, continuously keyed or bonded, sheet polymer membraneof 2 mm minimum thickness, fixed directly to the base slab underside.

Preformed membrane seams shall be heat welded together to form animpermeable joint. Keys of preformed membranes shall be orientated parallelto the least horizontal dimension of the base slab.

4.2.10.11 All structural elements which are not required to have membranes but which are

below ground, such as pile caps and retaining walls, shall be provided with two

coats of a general purpose bituminous protective coating complying with Type1A of BS 3416: “Specification for Bitumen-based Coatings for Cold Application,Suitable for use in Contact with Portable Water”, to the soil faces to a minimum

dry film thickness of 400 Microns.

4.2.10.12 It is good practice to provide a minimum fall of 1 in 40 for all external horizontalsurfaces exposed to the weather, where water may pond. Should this requiredstructural fall of 1 in 40 cause detailing / buildability difficulties then it is

acceptable to have a minimum fall of 1 in 80. Provided that the short-fall in thegradient is to be made up in the protecting screed (75 mm minimum).

4.2.11 VOID ACCESS AND VOID VENTILATION

General

4.2.11.1 Access panels or doors shall be provided into all structure voids to facilitate

inspection and maintenance. All voids shall be provided with means to ensureventilation, in accordance with BS 8313: “Code of Practice for Accommodationof Building Services in Ducts”, and recorded in the Civil O&M Manual.Inspection openings shall not be smaller than 800mm in diameter or squaredimensions, but the minimum shall be determined from a risk assessment..

Access

4.2.11.2 Where the vertical dimension of voids is greater than 2 m from the level of the

access hole cover, vertical ladders shall be provided in accordance with therecommendations of BS 5395: “Stairs, Ladders and Walkways”, Part 3,amended as follows:-

i) ladders shall be continuous to the void invert, in one vertical plane;

ii) where it is possible for persons to fall 2 m or more within the void,ladders shall be equipped with a fixed vertical rail for use with a sliding

fall arrest system and harness. No safety hoops shall be provided;






4.2/20

iii) the vertical distance between two successive landings shall not exceed6 m. The landings shall be provided with access holes for the user,which shall not exceed 500 mm in width, and shall be as small as

practicable in the other direction;

iv) all intermediate landings (where required) shall have an upward openingtrap-door fitted with a lock open device. The size of landing openingshall allow the clear passage of a stretcher; and

v) at the point of access, provision shall be made to accommodate the useof a man-rescue device over the centre of the opening.

vi) The design of all ladders higher than 2m shall be subject to a riskassessment to determine the need for a fall arrest system.

4.2.11.3 Access shall be provided to all levels and locations in all shafts such as vent,pier and emergency access shafts and vent tunnels to facilitate their inspectionand maintenance.

4.2.11.4 Ladder materials shall be coated galvanised mild steel in accordance with theM&W Specification in exposure conditions 1 or 2 and non metallic or stainlesssteel in exposure conditions 3, 4 or 5 as defined in Subsection 4.8.

4.2.12 PRECAST PARAPET FINISHES

4.2.12.1 Precast concrete parapets to railway viaducts and bridges shall have a profiledfinish with exposed aggregate, see Fig. 4.2.12.F1. On large exposed areas

greater than 10 m², which are otherwise unfinished concrete areas, a patternedfinish shall be specified. Special details around construction joints should alsobe implemented to improve the appearance of the element. In all cases,proposals for patterned finishes shall be subject to the Corporation's approval.

4.2.12.2 Details of the quality of finish required for concrete structures are given inSection 9 of the M&W Specification. Where it is considered that alternativefinishes are necessary or desirable approval of the Corporation shall beobtained before adopting such alternatives.

4.2.13 PERIMETER FENCE AND PARAPET REQUIREMENTS

4.2.13.1 Every part of the system where trains run, except station platforms, shall be

protected from access by, or objects placed, or thrown by, or vehicles driven bymembers of the public. The location and general arrangement of parapets,missile screens, anti-dazzle screens, security fences and noise barriers shall bein accordance with Section 3 of the NWDSM.

4.2.13.2 The foundation design for missile screens, anti-dazzle screens, security fencesand noise barriers shall allow for easy replacement of damaged or faulty parts.

All the above barriers in close proximity to the tracks (i.e. within 2.5 m from the






4.2/21

centre line of the track) shall be designed to be removable to facilitate trackmaintenance.

4.2.13.3 Parapets to railway viaduct shall be formed reinforced concrete. Glass fibre

reinforced concrete shall not be used.

4.2.14 UTILITY AND SERVICES CONNECTIONS

Utility and Services Connections at Stations

4.2.14.1 In general, the Designer shall be responsible for incorporating into their designthe requirements of the Corporation for utilities and services into and from thestations and other elements of the system. All provisions for utility and service

connections shall conform to the requirements of the relevant controllingauthority.

Water and Drainage Pipes

4.2.14.2 To mitigate against the effects of a pipe burst in a station or ancillary building,all incoming water supply pipes shall be provided with secure but accessibleisolating valves and chambers located within the Corporation's premises topermit closure of the supply by Corporation staff. The chamber shall be

positioned and detailed such that water from a burst in the supply pipe to thevalve cannot drain into the structure. In addition, the connections to the supplypipe shall be electrically isolated by providing a non-conducting pipe, not lessthan 1 m in length, at the interface. Consideration and liaison shall be given to

the NWDSM Section 7 requirements regarding these requirements.

Utilities and Services Crossings for At Grade Track

4.2.14.3 Where any utility or service crosses beneath tracks which are on ballasted

formation, a culvert or sleeve shall be provided around the utility or service inorder to prevent erosion of the railway formation due to leakage or pipe burstsand the like. The culvert or sleeve shall extend for a sufficient distance oneither side of the railway reserve, so that any excavation to expose the utility or service will not result in loss of stability of the railway formation. The top of the

culvert or sleeve shall be located below the maximum depth specified for therailway drainage.

4.2.15 DESIGN FOR COLLISION FROM RAILWAY

4.2.15.1 Structural elements within 10m of the centre line of track associated with Depotbuildings and facilities with no development above shall be designed with a highdegree of redundancy, so that the removal of one individual column will not lead

to progressive collapse of the remaining structure under all permanent andassociated live loads. However, no other collision amelioration measures or loads need be applied.

4.2.15.2 Structural elements within 10m of the track associated with Depot buildings and






4.2/22

facilities with development above shall be designed in accordance with collisionload requirements in Subsection. 4.4. Other collision amelioration measures inthe following clauses shall be adopted where practicable. However, these maybe relaxed on a case-by-case basis, subject to the approval of the Corporation,

to suit Depot operational requirements.

4.2.15.3 All other structural elements within 10m of the track centre line shall bedesigned for collision from railway vehicles in accordance with the following:-

i) structural elements shall not be located within 5m of the track centre line.

However, where space limitations or structural framing considerationsmake this impracticable, the structural elements shall be continuouswalls or beams, rather than discrete columns, so as to mitigate impactloads. Elements shall not be pin-jointed at both ends. Where E&Mopenings are required in structural walls, the invert level of the opening

shall be 1.2 m above adjacent rail level, leaving a stub wall which shall

be designed for the loading given in Subsection 4.4. Essential andoccasional access gaps in walls, up to a maximum of 1.5 m wide, maybe provided to E&M areas without providing specific collision mitigation;

ii) where discrete columns cannot be avoided within 5 m of the trackcentre line, the column shall be designed for collision loading inaccordance with Subsection 4.4 and the structure designed so that theremoval of one individual column will not lead to the progressive

collapse of the remaining structure under all relevant permanent andassociated live loads;

iii) the ends of structural walls within 5 m of the track centre line shall be'cut-water' shaped or chamfered, as is consistent with track geometry, to

deflect derailed rail vehicles back towards the track centre line and tomitigate impact loads. Typical details are shown in Fig. 4.2.15.F1; and

iv) discrete columns within 5 m of the track centre line shall be providedwith a solid mass concrete cut-water or chamfered plinth, as is

consistent with track geometry, to a height of 1.2 m above adjacent raillevel to mitigate impact loads. Plinths shall be made structurallydiscontinuous from the columns by the provision of a 25mm gap.Typical details are shown in Fig. 4.2.15.F2.

4.2.15.4 Notwithstanding the requirements of Cl.4.2.15.1 to Cl.4.2.15.3, greater railwaycollision loads may need to be considered if there is a low degree of redundancy in the structure. In this case the collision loading and mitigationmeasures to be used shall be subject to the approval of the Corporation.

4.2.16 ELECTRICAL AND MECHANICAL SERVICES REQUIREMENTS

General

4.2.16.1 The requirements for Electrical and Mechanical (E&M) services comprising

equipment and cables and the like must be considered in the development of






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the structural design and the detailing of civil engineering works. Theserequirements may be liable to change as the E&M designs are developed for each specific element of the system.

4.2.16.2 All current requirements for E&M services shall be incorporated into the designas they become available. All provisions in the structural design for E&Mservices must be approved by the Corporation.

Typical Requirements

4.2.16.3 Consideration shall be given to, but shall not be limited to, the following:

i) the positions and detailing of structural opening for electrical andmechanical services;

ii) the fixing position of electrical and mechanical plant and the delivery

route for installation and removal during operation;

iii) stray current monitoring and mitigation;

iv) the incorporation of an adequate water drainage system;

v) the design of reinforcement in rail plinths and deck to avoid interferencewith and attenuation of the signalling circuits;

vi) special care to be taken with the location of gullies in points andcrossing areas;

vii) the incorporation of earth mats below the building structure boxes;

viii) in certain areas, reinforced concrete air ducts formed, in part, by theprimary structure;

ix) plinths for mounting of electrical and mechanical plant;

x) specific durability measures (in terms of concrete cover, protectivecoatings for walls, slabs and plinths etc) for rooms housing aggressivechemicals, as noted in the room data sheets in Sections 5 and 8 of the

NWDSM or areas handling sea-water, e.g. pump houses and vent

buildings;

xi) the incorporation of 100 mm high upstands to service openings toprevent water seepage, making due allowance for floor finishes as

necessary; and

xii) structure openings, OHL recesses, SAB/TAB recesses and the like.

4.2.16.4 Confirmation of the detailed requirements shall be sort at the earliest stage of

the design of the requirements given in Cl.4.2.15.2. All designs shallincorporate these requirements.






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Fixings for Cable Brackets and other E&M Services

4.2.16.5 Fixings for cable brackets shall generally be provided at the following intervalsin tunnels, stations, and bridge or viaduct structures:

Power cables 2 mPilot and control cables 1 m

However specific requirements will vary, therefore requirements for fixings shallbe agreed with the Corporation early in the design process.

4.2.16.6 Non-metallic sockets for cable bracket and other light duty E&M bracketsupports shall be used in reinforced concrete. Hot dip galvanized fixings shallbe used in unreinforced concrete. For precast segmental linings the

requirements of Subsection 4.3 apply.

4.2.16.7 Safe working loads for fixings shall be derived from the characteristic failureloads using the following factors of safety (FOS) :

Fixings (Required FOS) Dead load = 3.0Dynamic load = 6.0

Where fixings are subject to a combination of dead and live load the FOS maybe interpolated between the values given above.

Plant Access

4.2.16.8 All structures shall be adequately designed and detailed to cater for the delivery,temporary storage, positioning, installation, and removal of heavy electrical andmechanical plant, such as temporary openings and access routes.

4.2.17 SPECIALISED CONSTRUCTION ELEMENTS

4.2.17.1 Some Contractors have developed specialised methods or designs for theconstruction of particular elements of structures, such as diaphragm walls andpiling. For such elements, design drawings shall indicate the forces andmoments to be resisted, in sufficient detail to allow alternative designs to be

produced by the Contractors. Particular elements or structures to which this

applies shall be identified and agreed with the Corporation prior to preparationof the drawings.

4.2.18 ENVISAGED METHOD AND SEQUENCE OF CONSTRUCTION

4.2.18.1 The method and sequence of construction assumed in the design shall beclearly defined on a separate set of Envisaged Construction Sequence and

Temporary Works' drawings to be made available at tender stage 'for information only'. However, any constraints that the design may place on theconstruction sequence or on temporary loading conditions shall be identified

and clearly marked in the Design and Tender or Contract documents as






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appropriate. Full account shall be taken of any temporary loading byconstruction plant, in accordance with Subsection 4.4.






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4.2/27






4.2/28






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FIGURE 4.2.15.F1

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FIGURE 4.2.15.F2

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Section 4: Civil Engineering D/MTRC/NW/DSM/ST/403/A54.3 Specific Design Criteria


4.3/1

4.3 SPECIFIC DESIGN CRITERIA

4.3.1 SCOPE

4.3.1.1 This Subsection defines the specific requirements for the design of thefollowing structures:

- cut and cover structures;- underground openings;- immersed tube tunnels;- ground level and overhead structures; andstructural movement joints.

4.3.2 CUT AND COVER STRUCTURES

General

4.3.2.1 This subsection sets out the specific requirements for the design of cut andcover structures such as tunnels and ancillary buildings of this form.

4.3.2.2 The preferred method of construction is conventional, ‘bottom-up’ withinexcavations. ‘Top-down’ construction shall only be used where it can beshown to have significant programme and whole-life cost benefits, and wherecontrol of ground movement is critical.

4.3.2.3 Where top-down construction is shown to provide sufficient benefits towarrant its use, subject to the approval of the Corporation, particular consideration shall be given to the following:

i) the design and detailing of practical slab to diaphragm wallconnections;

ii) the possibility of top-down walls being constructed out of plumb by upto 1 in 80. All tolerances must be allowed for in the effective length of the slab spans and due allowance must be made to overcome theloss of clearance to the structure gauge;

iii) a rebate shall be provided in the wall section at all slab/wall interfacesto ensure an adequate seating arrangement;

iv) watertightness of external joints. At wall/slab joints, a hydrophilic stripshall be glued with resin mortar on the surface of the rebate nearestthe ground, at a minimum distance of 40 mm from all reinforcement,before casting the slab; and

v) a drainage channel and hydrophilic strip shall be provided above theslab/wall connections. A typical detail is shown in Fig. 4.9.2.F1.

vi) Notwithstanding the above, the wall joints shall always be considered

a source of leakage. The wall shall be designed such that leakage isstemmed or controlled to prevent corrosion of reinforcement.





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Compatibility with Method of Construction

4.3.2.4 The design of tunnels and underground structures in which the permanentwalls and slabs are also used as temporary supports to excavations shall be

fully compatible with the method of construction likely to be adopted.

4.3.2.5 Permissible methods of construction, including contiguous bored pile, secantpiles, packed-in-place piles (PIP), and diaphragm walling shall utilise groundtreatment where necessary to control ground-water flows which may affectstability. In shallower excavations alternative methods may be used. Theuse of ground treatment to control water flows by reducing permeability inthese shallower excavations shall be kept to a minimum.

4.3.2.6 Different methods of construction, including form and sequence, type of plantand programme, will produce different design requirements. Full details of the proposed methods of analyses for the permanent walls when these areused as retaining walls in the temporary condition shall be submitted in theDesign Statement (DES). Well-proven methods shall be used and these shalltake full account of the construction methods proposed, the relative rigidity of the structure, any relevant structure-soil interaction and adjacent groundmovement limitations.

4.3.2.7 The method and sequence of construction assumed in the design shall beclearly defined. Any constraints that the design may place on theconstruction sequence shall also be identified and clearly marked on theTender and Contract drawings. Minimum support load, pre-load, stiffness,and permissible deflection limitations shall be defined in the design and/or

tender and/or contract documents as appropriate. Details of the requiredpresentation style of construction sequence drawings are given in the CADDManual.

4.3.2.8 If any cut and cover structures are constructed within the harbour or open seaareas then the requirements as specified for immersed tube tunnel buoyancydetailed in Subsection 4.3.4 shall additionally apply to the cut and cover structures.

4.3.3 UNDERGROUND OPENINGS

Definitions

4.3.3.1 Underground openings are defined as tunnels, caverns, shafts, adits and allother excavations formed below ground that are not basements, cut andcover tunnels or immersed tube tunnels and the like.

4.3.3.2 The following definitions for support and lining shall be used in this section.

i) Temporary or Initial Support

- Support installed to stabilise an undergroundexcavation by controlling deformations due to soil,groundwater pressures, rock mass in situ stresses,rock loosening or adjacent underground openings.

Normally installed close to the working face or within





4.3/3

the rear of the tunnel shield. Typically comprise steelrib supports or lattice arch girders with or withoutlagging; dowels; nails or rock bolts; plain or reinforcedshotcrete, canopy tube and forepoling spiles, or anycombination of these.

ii) Primary Lining - Permanent support constructed either close to theworking face or within the rear of the tunnel shield or tunnel boring machine and comprise either segmentallinings of precast concrete, spheroidal-graphite cast-iron (SGI) or steel; or plain or reinforced, cast in situor sprayed concrete. Primary linings may also controldeformations of the opening due to ground and/or groundwater pressures.

iii) SecondaryLining

- Permanent support typically comprising plain or reinforced poured in-situ concrete or plain or fibrereinforced sprayed concrete which are constructed ata distance from the working face or from the rear of ashield where deformation of the opening has beenstabilised by temporary support and/or primary lining.

General

4.3.3.3 This subsection sets out the specific requirements for the design of permanent underground openings.

4.3.3.4 All underground openings shall be designed and constructed in accordancewith BS 6164: “Code of Practice for Safety in Tunnelling in the ConstructionIndustry” and the NWDSM.

4.3.3.5 All permanent underground openings shall have a design life of 120 years.

4.3.3.6 The permanent support and lining to the underground opening may comprisethe primary lining, the secondary lining or a combination of the two. Thepermanent support and lining may also comprise permanent dowels, nails or bolts, fibre or mesh or rebar reinforced or plain shotcrete, cast-in-situ concreteand steel segments.

4.3.3.7 It shall be assumed that the temporary support does not contribute to thecapacity of the permanent support or lining in any way, unless agreedotherwise by the Corporation.

4.3.3.8 Generally all underground openings shall be designed to be sealed against allwater ingress and the full water pressure head occurring around the openingperiphery. The design shall include the provision of a waterproof membraneand a durable structural lining. However, for underground openings in rock(as defined in Subsection 4.6) where the structural invert slab is above thehighest astronomical tide level (HAT), or where it is uneconomical or technically impractical to either design the invert permanent lining towithstand the full water pressure, or to provide other means for dissipating thewater pressure, then a permanent pressure relief system may be incorporatedinto the design located outside the permanent lining, subject to the approvalof the Corporation, providing that it can be demonstrated that:





4.3/4

i) water inflows will not cause unacceptable drawdown or settlement;

ii) the 120 year design life of the structure will not be affected; and

iii) the associated whole-life maintenance and operating costs are more

than compensated by the reduction in construction costs, and accessfor inspection and maintenance is provided.

4.3.3.9 Generally, all permanent underground openings shall be designed for the fullwater pressure head around the opening periphery. The minimum water pressure head to be considered shall be equivalent to a water level 10 m abovethe crown of the underground opening. Where a pressure relieved openingform is accepted by the Corporation the lining shall be designed for theminimum water pressure head as defined above down to axis level, reducing tozero water pressure head at the invert.

4.3.3.10 In all underground openings where a pressure relieved system is used apositive drainage system of collecting pipes shall be designed to draingroundwater or pressure relieved water from behind the permanent lining and,within and from beneath the structural invert slab to the tunnel sump(s). Access holes for maintenance to the drainage system shall be providedthrough the structural invert slab at a maximum longitudinal spacing of 50 m.Pressure relief holes through the permanent lining of underground openings,including the invert, will not be permitted under any circumstances.

4.3.3.11 In all underground openings, provision shall be made for back grouting(contact grouting) between the permanent lining extrados and anywaterproofing membrane.

4.3.3.12 Where possible, consideration should be given to co-locating niches, e.g.sumps, passageways, fan niches and suchlike, to minimise the need for manyindividual niches.

4.3.3.13 Where it is impractical to design the rock permanent lining to withstand the fullloading then, subject to the approval of the Corporation, permanent rockdowels or bolts shall be designed in accordance with the relevant provisions of subsection 4.6.10.

Lining Types

4.3.3.14 All linings to underground openings shall be designed in accordance with theNWDSM and the following:

i) the British Tunnel Society / Institution of Civil Engineers, TunnelLining Design Guide; and

ii) “Hong Kong Code of Practice for the Structural Use of Concrete”.

4.3.3.15 All permanent underground openings shall have permanent and durablestructural linings which, depending on the nature of the surrounding ground,shall be formed from one of the following options:

i) in situ unreinforced or reinforced concrete





4.3/5

ii) Segmental precast concrete linings.

A minimum structural lining thickness of 250 mm shall be adopted.

4.3.3.16 Segmental lined underground openings shall possess measures to ensurewater tightness. Gaskets shall be purpose-designed EPDM rubber and ahydrophilic strip shall be incorporated in the joints. The concrete mix shallcontain river sand and the maximum water: cement ratio shall be limited to0.35 maximum. Other measures to promote construction quality shall be theuse of plastic spacers and welded reinforcement cages.

4.3.3.17 The following will not be accepted as permanent linings unless fully justified tothe Corporation and other approving authorities as appropriate:

i) unreinforced concrete segments;

ii) fibre reinforced concrete segments;

iii) Spheroidal – graphite cast iron bolted segments.

4.3.3.18 Where it can be demonstrated to the Corporation’s satisfaction that thepreferred options in Cl. 4.3.3.15 are technically impractical, the options in Cl.4.3.3.17 will be considered. Full details of the option shall be submitted to theCorporation for approval before proceeding with the detailed design. Thesedetails shall include an explanation of why the preferred options aretechnically impractical, how the design life will be achieved and how accessfor long-term monitoring and maintenance will be provided.

4.3.3.19 Other underground structures (such as portals, head-walls, ventilation or outfall works, sump pits, and invert concrete) which do not form a part of thefinal lining structure of underground openings may be constructed of reinforced concrete in accordance with the NWDSM only if it can bedemonstrated to the satisfaction of the Corporation that the use of plainconcrete is impractical.

4.3.3.20 SGI lining, where permitted, shall conform to BS EN 1563: “FoundingSpheroidal Graphite Cast Irons”. Depending on ground conditions, methodsof construction, and specific location in the works, precast concrete or SGIsegment lining may be either a bolted or expanded articulated type and may

also be parallel (plain) or tapered.

4.3.3.21 Segmental shafts sunk as caissons shall have choker rings and cutting edgesprovided.

4.3.3.22 In specific locations, SGI and bolted concrete segment pans may need to beinfilled to provide a smooth internal surface to aid air flow. Bolt pockets inwhich water may possibly accumulate shall be filled with concrete.

4.3.3.23 Where steel bar reinforced precast concrete segments are permitted for permanent lining, the bars shall be electrically connected within eachsegment and between adjacent segments to allow for the collection of stray





4.3/6

currents and for the possibility of installing a cathodic protection system in thefuture; details shall be discussed with and agreed by the Corporation.

Temporary Lining Loads

4.3.3.24 All temporary linings shall be designed to withstand all environmental andapplied loadings and effects appropriate to the needs of its design Life withoutdistress. Linings shall be designed for, but not be limited to, the followingloadings and situations:

i) superimposed surface loading based on traffic loading and theloading due to existing buildings over and/or adjacent to theunderground openings;

ii) appropriate ground loads;

iii) groundwater pressures;

iv) the structural requirements for resisting buckling;

v) short-term ground yield or squeeze;

vi) unequal grouting pressures;

vii) adjacent excavation(s);

viii) openings in or extensions to the lining;

ix) short-term loads induced by the construction procedure including, butnot be limited to, localised de-watering, ground freezing, compressedair working, compensation grouting etc;

x) temperature, shrinkage and creep;

xi) handling loads, especially in the case of unreinforced or reinforcedsegments;

xii) loads (impact and thrust) from construction equipment such as theTBM; and

xiii) installation loads such as bolted segment connections.

Permanent Lining Loads

4.3.3.25 The final permanent structural lining shall be designed to withstand allenvironmental and applied loadings and effects without distress. Linings shallbe designed for, but not be limited to, the following loadings and situations:

i) superimposed surface loading based on traffic loading and theloading due to existing buildings over and/or adjacent to the opening,or any specified future loading whichever is the greatest;

ii) the possibility of future developments (refer to Subsection 4.4);





4.3/7

iii) ground and ground water loads (using Ultimate and ServiceabilityLimit States for deepest and shallowest sections; highest and lowesthydrostatic heads, differing geological conditions etc);

iv) earthquake loading;

v) railway loading including loading due to derailment and constructionvehicles;

vi) the structural requirements for resisting buckling;

vii) short and long-term ground yield or squeeze;

viii) unequal grouting pressures;

ix) adjacent excavation(s) including tunnel to tunnel (or other opening)interaction;

x) openings in or extensions to the lining;

xi) short and long-term loads induced by the construction procedure;

xii) temperature, shrinkage and creep;

xiii) segment handling and stacking (including single point or vacuumlifting / erector devices, eccentric segment stacking and allowablestacking heights), especially in the case of unreinforced or reinforced

segments;

xiv) loads (impact and thrust) from construction equipment such as theTBM (including eccentric loading of shove ram jacks due to segmentmisalignment);

xv) installation loads such as bolted segment connections (including thepossible effects of shear on the circumferential joint connections fromhaving staggered longitudinal joints);

xvi) imposed distortion caused by lack of circularity;

xvii) annulus and subsequent back-grouting;

xviii) poor segment ring build (including analysis of out of planecircumferential loading and bursting stresses due to axial loadingcaused by ‘birds-mouthing’ and stepping of segment joints);

xix) segment casting inaccuracies;

xx) prevention of floatation (including possibility of ground heave);

xxi) temporary and permanent services; and





4.3/8

xxii) reinforced concrete design (including checks on: hoop stresses,bursting, overall buckling, torsion load from TBM head rotation,compression of gaskets by bolts, circumferential groove capacity,rotation at each segment joint under load etc).

xxiii) Loss of strength due to a fire.

4.3.3.26 In addition to the loadings noted in Cl. 4.3.3.25, permanent soft ground liningsutilising segmental sections shall be designed to accommodate an additionaldeflection of ± 20mm on diameter to allow for future development. This shallbe achieved by amending the horizontal/vertical load as specified in Cl.4.3.3.25 to produce the aforementioned ± 20mm deflection on diameter. Alternative ways of analysing the effects of additional deflection may beproposed for the acceptance of the Engineer.

Tunnel Excavation and Lin ing Design Methods

4.3.3.27 The design of underground opening excavations, linings and related worksshall take into consideration the method of construction, the required life span,the proposed use, the ground conditions, the sequence and timing of construction and the proximity of adjacent structures.

4.3.3.28 The underground opening shall be of sufficient size to accommodate alloperational envelope requirements and provision for services, fittings, plant,walkways, ventilation, drainage etc. In addition, due cognisance should bemade to the construction tolerances given within the M&W Specificationparticularly in relation to TBM drive tolerances.

4.3.3.29 The analysis or design methods for underground openings excavation andlinings shall take into account all interactions including, but not be limited to,those detailed in Cl. 4.3.3.24 to Cl.4.3.3.26 above. The Designer shall use arecognised design method. The following are considered to be acceptablemethods for analysis:

i) Soft ground (homogenous and stratified soils):

a) Continuum model by Muir Wood A M, 1975, The Circular Tunnel in Elastic Ground, Géotechnique, Vol. 25, combinedwith the discussion by Curtis D J, 1976, Discussion on Muir Wood, Géotechnique, Vol. 26;

b) Anagnostou G & Kovári K, 1996, Face Stability in Slurry andEPB Shield Tunnelling, Geotechnical Aspects of UndergroundConstruction in Soft Ground, Balkema;

c) Leca E and Dormieux L, 1990, Upper and Lower BoundSolutions for the Face Stability of Shallow Circular Materials inFrictional Material, Géotechnique, Vol. 40;

d) Morgan H D, 1961, A Contribution to the Analysis of Stress ina Circular Tunnel, Géotechnique, Vol. 11;





4.3/9

e) Duddeck H and Erdmann J (1982) Structural design modelsfor tunnels. Tunnelling 1982 1M1;

f) Terzaghi’s equation (lowerbound) or full overburden(upperbound) taking into account the ground arching effect;

and

g) Finite element methods.

ii) Hard rock

a) Grimstad E and Barton N et al, Q-System;

b) GEO, Guide to Cavern Engineering; and

c) Finite element methods.

4.3.3.30 In the event that computer analyses are used for the design, the Designer shall also provide manual check calculations using established engineeringand geotechnical principles to verify the results.

Incremental Excavation and Support Techniques

4.3.3.31 Tunnelling methods that involve incremental excavation and support, such asthe New Austrian Tunnelling Method (NATM) or the Sprayed Concrete LiningMethod (SCLM), require continuous observation of both the ground andsupport. Such underground openings shall be designed and constructed inaccordance with the NWDSM and the following:

i) the Institution of Civil Engineers design and practice guide, SprayedConcrete Linings (NATM) for Tunnels in Soft Ground;

ii) the UK Health & Safety Executive report, Safety of the New AustrianTunnelling Method (NATM) tunnels; and

iii) “Hong Kong Code of Practice for the Structural Use of Concrete”.

4.3.3.32 The design and construction methodology shall take account of the following:

i) length of advance;

ii) whether advance should be partial face or full face;

iii) inclination of face;

iv) speed of ring closure;

v) face support; and

vi) adjacent activities, such as excavations and ground treatment.

4.3.3.33 The design shall be reviewed and modified during and after construction as a

result of comprehensive monitoring and interpretation of the following:





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i) the behaviour of the ground at the tunnel face in comparison with thedesign assumptions;

ii) surface settlements;

iii) lining deformations; and

iv) measurement of ground loadings and displacements.

Appropriate contingency plans shall be prepared and implemented to modifythe design and construction should the behaviour of the ground or the liningbe shown by the monitoring to be substantially different or in excess of thosepermitted.

Ribs and Lagging

4.3.3.34 The design of a temporary support system using ribs and lagging in rock shalluse a recognised design model. The following are considered to beacceptable methods for analyses:

i) Terzaghi K, 1946, Rock Tunnelling with Steel Supports, Section 1,Commercial Shearing and Stamping Co.;

ii) Proctor and White, 1946, Rock Tunnelling with Steel Supports,Section 1, Commercial Shearing and Stamping Co.; and

iii) “Hong Kong Code of Practice for the Structural Use of Steel”.

4.3.3.35 The design of the temporary support system using ribs and lagging shall takeinto consideration, but not be limited to, the following:

i) axial and bending stresses in the steel arch ribs induced by the rockloads;

ii) lateral stability and bracing of the steel arch ribs;

iii) amount of preload to be applied to steel arch ribs and methods of supplying this load;

iv) method of blocking and spacing of blocking points;

v) length of advance;

vi) whether advance should be partial face or full face;

vii) face support;

viii) bearing capacity of the rock at blocking points and, in the case of horseshoe-shaped cross section, under the footplates;

ix) the stand up time of the unsupported part of the excavation;





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x) the method of lagging between ribs to prevent ravelling and/or softening of the ground; and

xi) the ground water regime and permeability of the ground.

Grouting Pressures

4.3.3.36 The design of both temporary and permanent linings shall be such that uponcompletion they are capable of withstanding the grouting pressures andpressure distribution during the following:

i) construction (primary grouting); and

ii) future maintenance/remedial works (secondary grouting).

4.3.3.37 The design grout pressures and the pressure distribution to be adopted for primary and secondary grouting shall be stated in the DES and subject to theCorporation's acceptance.

4.3.3.38 The grouting pressure must be greater than the external hydrostatic pressureacting on the lining at the time of grouting. For precast segmental segments,the designed grout pressures and loading cases shall be adopted as follows:

i) for the primary annulus a grouting pressure of not less than 1.5 Bar above hydrostatic applied fully around the annulus of the tunnel.

As the lining has just been built it can be assumed that ground loadingdoes not apply and there is no shear resistance between the lining

and ground.

ii) for secondary grouting a pressure of not less than 2 Bar abovehydrostatic applied locally.

As the lining would have been in place for some time it can beassumed that full ground loading applies and there is full shear resistance between the lining and ground due to previous annulusgrouting.

4.3.3.39 The annular void between segmental linings and the ground should begrouted as soon as practicable. In shield-driven underground openings this

should be taken to mean simultaneously with shield advance. In undergroundopenings excavated by hand this should be taken to mean after eachsegment ring is completed. The grout system should be devised to ensurethat all voids are filled and to minimise ground movements from closure of theannulus.

Lining Waterproofing and Details

4.3.3.40 The detail design of all linings shall ensure the standard of watertightnessrequired in Subsection 4.2. Notwithstanding these requirements, linings shallbe designed and detailed such that the underground opening shall be freefrom drips and seepage. Water ingress shall be minimised such that the

underground opening above axis is dry and only damp patches shall develop





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at any time elsewhere. Drain pipe systems on the tunnel intrados to divertleakage water will not be permitted.

4.3.3.41 Underground openings shall have a waterproof membrane around the fullperiphery, except underground openings which have a pressure relieved

drained invert where a drainage fleece shall additionally be provided betweenthe membrane and the excavated face; both extending from ‘crown' to ‘invertformation level'. The permanent pressure relief system shall be provided over the whole width of the formation at invert. This shall take the form of adrainage layer with a minimum thickness of 200 mm comprising compacted(20-40 mm) clean aggregate. A porous transverse cross drain, of minimumdiameter 75 mm, shall also be provided within the drainage layer at amaximum of 20 m centres laid to a fall of 1:50, to a porous, centre longitudinaldrain of 200 mm minimum diameter with a minimum fall of 1:100. Catchpitsshall be provided to the centre drain with minimum internal size 500 mm longx 500 mm wide at maximum 50 m centres.

4.3.3.42 Poured in situ concrete lining shall have an approved external waterstopwelded to waterproofing membrane at all longitudinal and circumferentialconstruction joints.

4.3.3.43 Where a precast reinforced concrete lining is permitted for permanent support,segment details shall include the following protective coatings if groundconditions are defined as 'aggressive' in accordance with Subsection 4.2:

i) extrados: barrier coating, capable of withstanding abrasion (similar or equivalent to 400 microns of epoxy based coating applied in aminimum of two coats); and

ii) intrados and other surfaces: surface impregnation by a hydrophobic,pore-blocking agent; or

iii) Alternatively, the use of silica fume in concrete mix for precastreinforced concrete lining may also be considered as a measure toimprove durability subject to the results on relevant material test,including Chloride Diffusion Test in according with ASTM C1202-05.

4.3.3.44 Segmental lining whether for Temporary, or Permanent Works support, shallinclude cast-in threaded grout ports which do not penetrate the full depth of the segment. The threaded section of the grouting ports shall be deep enough

to allow the inclusion of a non-return valve and a screw-in cap. Intrados jointsof the segments shall be provided with grooves for caulking. All bolts, plugsand caps shall be hot dip galvanized and bolts shall be sealed against water ingress with rubber / hydrophilic grommets. Segments shall be fitted with asuitably designed waterproofing gasket, moulded in one piece and bonded tothe segment within a dedicated precast groove on all segment to segmentfaces located outside any bolts used to connect segments. A secondarywaterproofing hydrophilic strip shall be included on all segment to segmentfaces.

4.3.3.45 Bolted SGI lining shall be machined on all joint faces and grooves shall beprovided for caulking and gaskets or hydrophilic joint sealing material.

Gaskets and sealing materials shall be designed to resist infiltration of





4.3/13

groundwater under pressure and chemical attack from water-borne pollutants.Caulking grooves should not be filled after installation of the lining. Theyshould only be caulked if seepage starts. The preferred caulking compoundis a cementitious asbestos free cord, dampened and packed into the caulkinggroove. Grout holes should be fitted with one-way valve screw plugs to

maintain the integrity of the outer waterproof seal.

Lining E&M Requirements

4.3.3.46 Linings cast in-situ shall preferably have cast-in inserts for E&M fixings. Alternatively inserts may be drilled and grouted. Inserts within the cover concrete zone shall be stainless steel. Where baseplates or fixings aregrouted and effectively provide cover, inserts shall be galvanised. All boltsmay be galvanized if painted, otherwise bolts shall be stainless steel wherethere is a stainless steel insert. Stainless steel shall be separated fromcarbon steel when exposed to the atmosphere.

4.3.3.47 Inserts to segmental linings shall be drilled and grouted as described insection 4.3.3.46. For SGI lining, 30 mm diameter holes shall be cast into thecentral ribs of each segment where there is a central rib, or into the insidesurface of the segment. Alternatively, fixings shall be achieved by the use of long bolts at selected positions around the opening perimeter. For segmentalconcrete lining, 16 mm diameter non-metallic sockets shall be cast-in at thequarter point of each ring to avoid clashing with the grout plug.

4.3.3.48 The permanent lining shall be designed so that any required penetrations(such as overhead line fixings) do not penetrate to closer than 100 mm of thepermanent lining extrados.

4.3.3.49 The location and number of fixings shall be in accordance with Section 7 of the NWDSM and agreed with the Corporation on a case-by-case basis for alllinings types.

Poured In situ Concrete Lining Construct ion Constraints

4.3.3.50 Particular attention shall be paid to detailing control shrinkage cracks byspecifying as a minimum:

i) low cementitious and water content in concrete mixes; and

ii) temperature control of placed concrete.

4.3.3.51 The Tender and Contract drawings shall specify that overbreak must be filledbefore casting of the nominal lining thickness, in order to avoid differentiallining thickness and consequential shrinkage and cracking. The permissibletolerance on the nominal lining thickness is -0 mm +100 mm. Combinedoverbreak fill and lining pours shall not be permitted.

Ground Treatment and Temporary Suppor t

4.3.3.52 A statement shall be included in the anticipated Construction Method, basedon all the available ground information, of the expected need for and method

of providing: ground treatment in advance of the underground openings





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excavation, and temporary support during excavation. This informationtogether with the assumptions on which it is based shall also be shown on theenvisaged construction sequence drawings described in Subsection 4.10.

4.3.3.53 If the use of sprayed concrete and/or rock bolts/dowels is proposed as part of

any permanent support system, a detailed materials and workmanshipspecification and method of measurement shall be produced, based on theM&W Specification outlines, for incorporation in the design and/or tender and/or contract documents as appropriate.

Compressed-air Working

4.3.3.54 When the use of compressed air is envisaged, consideration should be givenduring the design and construction phases to the safety risks involved in itsuse from both a structural and personnel well-being viewpoint. Compressedair installations shall be planned and operated in accordance with theNWDSM and the following:

i) BS 6164, Code of Practice for Safety in Tunnelling in the ConstructionIndustry;

ii) BS EN 12110 and BS EN 12336 when using compressed air withintunnelling machines;

iii) Anagnostou G & Kovári K, 1996, Face Stability in Slurry and EPBShield Tunnelling, Geotechnical Aspects of Underground Constructionin Soft Ground, Balkema; and

iv) Hong Kong, Factories and Industrial Undertakings (Work inCompressed Air) Regulations, Cap. 59M.

4.3.3.55 Compressed air is often applied for temporary excavation support when thepressurising fluid is removed from the face of a Slurry or Earth PressureBalance TBM for inspection / maintenance of the cutter-head or removal of obstacles. The design of the compressed air support system should takecognisance of the seepage of the compressed air into the ground at the faceand through the lining behind the face, and for the potential for the water saturation level of the ground at the face to be affected. Suitable methods areto be designed, e.g. bentonite-slurry filter cake, shotcrete, rapid hardeningcement, to prevent instability of the face and consequentially affect adjacent

ground or structures.

4.3.3.56 When using compressed air throughout the underground opening, such asduring hand-excavation or open-face shield tunnelling, the pressurebulkheads, and their connection to the lining, separating the working chamber from areas of lower pressure shall be designed to be of sufficient strength tosafely withstand the maximum pressure to which they may be subjected.

4.3.3.57 Bulkhead locations should be designed taking due cognisance for theprevention of ground bursts (‘blow-outs’), ground heave and safety of workers within the working chamber. Where there is a possibility of rapidflooding of the working chamber, for instance in subaqueous underground





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openings, the bulkhead shall be located sufficiently close to the face or shieldto permit escape of the workers in case of an emergency.

4.3.3.58 Whilst site investigation boreholes should be sited close to the line of theproposed underground opening, they should not be sited so close as to

intersect it, unless for some specific reason.

Ground Freezing

4.3.3.59 The design of artificial ground freezing techniques use within shafts or underground openings shall allow for soil, structure and ice interaction using arecognised thermal and structural design model taking due cognisance of thefollowing:

i) in situ ground water movement (decreasing the effect of the frozenground and potentially causing incomplete ice-walls);

ii) structural changes in the soil material, for instance compactionresulting from frost heave, ice lenses, thaw weakening and thawsettlement; and

iii) the effect of changes in the soil material and the resultantconsequence to the excavation opening, and on adjacent utilities andstructures.

4.3.3.60 Guidance on design methods for ground freezing may be found within thefollowing documents:

i) Harris J S, 1995, Ground Freezing in Practice, Thomas Telford; and

ii) Bickel T R, 1996, Tunnel Engineering Handbook, Chapman & Hall.

Tunnel Boring Machines

4.3.3.61 Tunnel boring machines (TBMs) shall be designed to withstand the loadsimposed by the surrounding ground and ground water through which themachine is intended to be used together with any loads imposed by the actionof driving the machine.

4.3.3.62 TBMs shall be provided with face support systems designed to be appropriate

to the ground conditions for which the machines are intended. Such systemsinclude: face rams, hydraulically-operated poling plates, face plates or faceboards, breasting plates or by the application of compressed air with asuitable face sealing material, e.g. bentonite cake, shotcrete, or rapidhardening cement, application of slurry pressure, or application of EarthPressure Balancing (EPB) mechanisms.

Safety requirements for the construction of TBMs and associated back-upequipment shall conform to:

i) BS 6164: “Code of Practice for Safety in Tunnelling in theConstruction Industry”;





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ii) BS EN 815: ”Safety of Unshielded Tunnel Boring Machines andRodless Shaft Boring Machines for Rock”;

iii) BS EN 12110: “Tunnelling Machines – Air locks – SafetyRequirements”; and

iv) BS EN 12336: “Tunnelling machines – Shield Machines, ThrustboringMachines, Auger Boring Machines, Lining Erection Equipment – Safety requirements”.

4.3.4 IMMERSED TUBE TUNNELS

General

4.3.4.1 This subsection sets out the specific requirements for the design of ImmersedTube Tunnels (IMT).

4.3.4.2 The following general criteria shall be adopted for the design of the IMT:

i) the method of design shall be based on limit-state philosophy;

ii) reinforced and prestressed concrete structures shall be designed inaccordance with “Hong Kong Code of Practice for the Structural Use of Concrete” as modified by the NWDSM. Structural steel design shallbe in accordance with “Hong Kong Code of Practice for the StructuralUse of Steel”. Where no specific requirement is given in the NWDSM,the design shall be to a recognised and proven code or standard and

to the approval of the Corporation;

iii) the form of IMT construction shall be steel shell or reinforced concrete.Concrete structures shall, as a minimum, include electrically isolatedprestressing in the longitudinal tunnel direction. Longitudinalprestress shall be designed to exclude longitudinal stresses from SLSand to give adequate ultimate flexural capacity;

iv) except as otherwise required by Section 3 of the NWDSM, railwaytracks shall be contained within separate cells by structural dividingwalls;

v) the structure shall make allowance for construction tolerances,placement tolerances and future movement of the IMT; and

vi) The Corporation will entertain value engineering proposals whichrequire alteration of the defined track alignments, subject tomaintenance of navigation clearances and the like. For instance,dredging levels may be proposed to minimize dredging or obtain thebenefit of a deeper founding layer. Any modification shall beexercised at the sole discretion of the Corporation.





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Hydraulic Regime - Model Tests

4.3.4.3 Physical hydraulic modelling shall be undertaken to determine the followingeffects of the construction and existence for the design life of the IMT:

i) variation in flow regime, taking particular care in the shore areas andthose areas affected by the IMT's presence;

ii) variation in the sedimentation regime identifying areas of accretionand erosion in the area of the IMT and those areas affected by theIMT's presence taking particular care in the shore areas. Effects onadjacent or far field areas, in particular those areas where the marineactivities are in progress, or planned to be;

iii) variation in the water quality regime in the IMT area and in areasaffected by the presence of the IMT; and

iv) effects on navigation shall be determined in any area where thepresence of the IMT affects the flow regime.

4.3.4.4 It is expected that any existing relevant hydraulic modelling will be usedwherever possible to determine the above factors rather than to instigatespecific studies. However consideration and presentation of the above detailsshall be given to the Corporation at the earliest time in the design stagedemonstrating how the above factors will be addressed, taking duecognizance of the time required to undertake such studies.

4.3.4.5 A detailed report shall be produced describing the model tests, results,

drawing conclusions and recommending design solutions and methods of construction that will mitigate against any unacceptable consequences of thescheme. A method statement shall be produced accordingly and included inthe design and/or tender and/or contract documents as appropriate.

IMT Hydraul ic Performance - Model Tests

4.3.4.6 The IMT performance shall be model tested hydraulically under all stages of float up, transportation, mooring and immersion. Particular care shall betaken to accurately model the influence of the ambient conditions existing atthe time of the various activities as well as extreme typhoon conditions thatmight exist if mooring during fit out is proposed. Similarly the influence of

immersion and transportation equipment that maybe present during thesetimes shall be accurately modelled. The physical model tests shall beundertaken using prototype/model scales that will allow the following factorsto be accurately determined:-

i) hydraulic stability of the IMT and equipment; and

ii) towing capacity required and the loads actually applied to the IMT.

4.3.4.7 A detailed report shall be produced describing the model tests, results,drawing conclusions and recommending design solutions and methods of construction that will mitigate against any unacceptable consequences of the





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scheme. A method statement shall be produced accordingly and included inthe design and/or tender or contract documents as appropriate.

IMT Foundation - Model Tests

4.3.4.8 If sand jetting or sand flow foundations are proposed then physical modeltests shall be undertaken at appropriate prototype/model scales that will allowthe following factors to be accurately determined:

i) proof that the pancake pattern provides adequate and stable IMTfoundation, consistent with the foundation assumptions;

ii) proof that delivery equipment including any discharge pipe usedwithin the IMT walls or outside the IMT, are adequate to produce therequired pancake pattern and foundation consistency; and

iii) proof that the IMT foundations are able to be formed without theinclusion of any silting process. Particular care shall be taken toensure that silts, as well as sands, are not included in the IMTfoundations.

4.3.4.9 A detailed model test report shall be produced detailing the model tests,results and giving details of the proposed works required to complete theWorks. A method statement shall be produced accordingly and included inthe design and/or tender and/or contract documents as appropriate.

Buoyancy

4.3.4.10 The factors to be used for determining required displacements and ballastingshall be as follows:

i) During Flotation and Towing

The minimum factor of safety against sinking of the completedimmersed tunnel unit, fully outfitted with temporary installations or other Temporary Works, and including the effects of any flotationdevices used, shall be not less than 1.02.

However the Tunnel Element (TE) shall have an adequate freeboardtaking cognizance of the sea state to which the unit will be subjected.

ii) During Sinking

The immersed TE shall have sufficient minimum negative buoyancy toensure stability during the sinking operation. The minimum negativebuoyancy shall be not less than 300 tonnes for a nominal 100 m longTE and of similar proportions for other lengths.

iii) After Sinking and Placing

The minimum factor of safety against flotation, without considerationof the backfill, shall be not less than 1.04.





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This factor of safety may be reduced to 1.02 for short periods duringconstruction under careful supervision and subject to the approval of the Corporation on a case by case basis.

iv) Completed Structure Without Trackform

For the temporary condition prior to placement of the track slab in thecompleted structure the factor of safety against flotation, withoutconsideration of backfill, shall be not less than 1.03.

v) Completed Structure

a) The minimum factor of safety against flotation, withoutconsideration of backfill, shall be not less than 1.04.

b) The minimum factor of safety against flotation, including theeffects of 1.5 m of backfill over the plan area of the unit, shallbe not less than 1.20.

4.3.4.11 In the above calculations the rails and their support system, E&M installations,and other removable or degradable items together with the frictionalresistance of the backfill shall not be considered. External ballast concrete onthe roof of the tunnel may be used providing that it is structurally connected tothe units. The required minimum thickness of tunnel protection and tunnelbackfill shall be placed above this external ballast concrete. This externalballast concrete shall be placed prior to immersion of the units.

4.3.4.12 The minimum requirements of the above Cl.4.3.4.10 shall be satisfied taking

into consideration the range of possible variations in densities of materials,seawater and their critical combinations. Reference shall be made to Table4.3.4.T1 for the range of the unit weight of seawater to be assumed.

4.3.4.13 All parameters affecting buoyancy shall be measured during TE constructionand appropriate calculations completed and submitted to the Corporation, toensure that the required buoyancy requirements noted in Cl.4.3.4.10 areachieved during construction and in the following stages of installation andoperation. Determination of buoyancy shall consider, but not be limited to,the following parameters and sensitivity thereof:

i) Concrete density and variation;

ii) Steel density and variation;

iii) Actual sea water density range;

iv) TE structural member actual volumes or theoretical volumes withallowable variations; and

v) Reinforced concrete weight.

4.3.4.14 The buoyancy, weight, and density monitoring requirements required shall bespecified in the Design and/or Tender and/or Contract documents as

appropriate in order for the Contractor to be able to demonstrate compliance.





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a) Anchor Impact (reference shall be made to Subsection 4.4)

b) Sunken Ship (reference shall be made to Subsection 4.4)

c) Flooded Tunnel

The situation of either one or both bores flooded shall beassumed. When considering one bore flooded, a hydrostatichead equivalent to the internal height of the bore shall beassumed. When considering both bores flooded, the fullhydrostatic head corresponding to the appropriate sea-water level shall be assumed.

d) Silting Loads

For sections of the tunnel beneath the seabed, not less than2m of additional depth of overburden shall be considered indetermining the imposed loads to account for possible futuresilt deposits.

4.3.4.20 The seawater design levels and densities for Victoria Harbour shall be thosegiven in Table 4.3.4.T1. The design levels for other locations shall besubmitted for the approval of the Corporation. The maximum seawater levelsinclude an allowance of 0.5 m for a rise in sea level due to climatic changeand therefore may not be applicable to the construction stage.

Table 4.3.4.T1 Design Seawater Levels and Densi ties

Condition Design Seawater Level (mPD) Weight kN/m³SLS ULS

Maximum +3.0 +5.0 10.05

Minimum +0.5 -0.5 9.900

Secondary Loads

4.3.4.21 Allowance shall be made for uneven foundation support of the tunnel unitswhich shall take account of the foundation conditions and method of installation to be used. Loss of support over a length of 10 m measured alongthe longitudinal axis of the tunnel, in stages up to the full width of tunnel shall

be assumed beneath sea or land areas.

4.3.4.22 The effects of differential movement in any direction shall be taken intoaccount in determining the imposed deformations. A minimum deflection of ±25 mm for a tunnel length of 100 m shall be assumed.

4.3.4.23 When determining longitudinal load effects, a seasonal change in the averagetemperature of the structure of at least 15°C shall be assumed. Whenconsidering the effects of temperature variation, a differential temperature of +16°C shall be taken between the inside and outside of the tunnel.

4.3.4.24 Design for durability shall be in accordance with Subsections 4.2 and 4.8

except as amended by this subsection. The IMT structure shall be





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considered as a Category A structure for concrete temperature control inaccordance with the M&W Specification.

4.3.4.25 Prestressing shall be designed to “Hong Kong Code of Practice for theStructural Use of Concrete” Class 2 requirements under all permanent loads.

4.3.4.26 The TE shall be enveloped in a waterproof membrane around the fullperiphery. However the TE shall be designed without regard to thiswaterproof membrane when considering corrosion of reinforcement and steelfittings, and the durability of concrete. The design life of any steel shell andits corrosion protection system shall be taken into account when determiningthe effective structural steel available during the design life of the IMTstructure. Appropriate additional steel thickness shall be provided in order toprovide adequate strength and stiffness for the design life given in Subsection4.2.

4.3.4.27 Steel used as TE external shell or as a waterproof membrane shall beprovided with a corrosion protection system of proven performance for asimilar design in an environment of comparable exposure. Alternatively or additionally, the thickness of the steel may be increased to allow for corrosion;the assumed rate of corrosion shall be submitted for the approval of theCorporation.

4.3.4.28 The class of concrete and corresponding cover to the reinforcement on bothfaces of the tunnel units external elements shall be specified in accordancewith the requirements for the exposure condition 4 as defined in Subsection4.8 Table 4.8.7.T2 - Concrete Durability Requirements in order to takeaccount of the possibility of seawater contamination. Internal walls may be

designed for the requirements of the exposure condition 1.

4.3.4.29 The need for provision of cathodic protection systems shall be consideredduring the design process. However, cathodic protection enablement works,as described in Subsection 4.2, shall be provided whether or not cathodicprotection is considered necessary.

Joints

4.3.4.30 The TE shall be provided with permanent flexible joints to reduce the stressesarising from shrinkage and creep, seasonal variations in temperature, and theimposed deformations due to differential movement of the foundations.

4.3.4.31 The joints shall incorporate at least two flexible water barriers of provendesign and material. At least one of the water barriers shall be installed in amanner which permits repair and replacement during the life of the structure.The space between the joints shall also be capable of being monitored for leakage past the external water barrier. The non-replaceable water barrier shall have a design life as noted in Subsection 4.2, while the replaceablewater barrier shall have a design life of not less than 40 years.

4.3.4.32 To avoid disruption to the rail alignment, the TE joints shall be designed torestrain differential vertical and lateral movements across the TE joint in thepermanent condition.





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4.3.4.33 Electrical isolation shall exist between individual TE, although provision shallbe made for making these units electrically continuous in the future by theprovision of external electrical connections.

4.3.4.34 Flexible joints shall be finished to present a smooth internal surface using

corrosion protected steel cover plates or other method as agreed with theCorporation. The finish shall provide a two-hour fire resistance period to the joint materials.

Walkways

4.3.4.35 The design shall provide for a walkway in each tunnel bore adjacent to thedividing wall. Reference shall be made to Section 3 of the NWDSM.

4.3.4.36 For loading purposes, the walkways shall be considered as platforms inaccordance with Subsection 4.4.

4.3.4.37 The top surface of the walkways shall be provided with a U4 concrete finishas defined in the M&W Specification.

Drainage

4.3.4.38 Drainage sumps with a minimum capacity of 25 m³, or that which is suitablefor the predicted inflow, whichever is greater shall be provided at the tunnellow point to accept tunnel wash down water and water draining into the tunnel.The number, layout, and location of drainage sumps and the provision for pumps and pipework for discharging the sumps shall be in accordance withSection 7 of the NWDSM and to the approval of the Corporation.

Emergency Access Doors

4.3.4.39 Emergency access doors may be required to be provided in the dividing wallbetween tunnel bores, at Evacuation Walkway level. All such emergencyaccess doors will be located as directed by the Corporation.

4.3.4.40 The doors shall have a two-hour fire resistance period and shall be designedto withstand the maximum pressure fluctuations caused by two trains passingat their design speeds.

4.3.5 GROUND LEVEL AND OVERHEAD STRUCTURES

General

4.3.5.1 This subsection sets out the specific requirements for the design of groundlevel and overhead structures such as bridges, footbridges and similar components of building structures.

Bridge Deck Continu ity

4.3.5.2 The type of trackform may determine the articulation arrangements of viaducts and bridges. However, deck continuity shall be adopted wherever

possible, as it possesses other beneficial features, such as reductions in deck





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construction depths, pier bearing widths and foundations, in addition to abetter running quality. Cantilever spans and half-joint arrangements will notbe permitted in bridges or other structures.

4.3.5.3 Deck continuity in prestressed structures generally requires prestressing

tendons located in the deck slab or in the top flange and top of web locationsof box girders. Account shall be taken of the increased vulnerability of thetendons to corrosion due to water which may penetrate the deck throughconstruction joints or cracks. Therefore, the number of vertical construction joints shall be minimised and, wherever possible, they shall be located awayfrom zones subject to hogging moments. All such vertical construction jointsshall be waterproofed in accordance with Cl.4.3.5.14.

Bridge Deck End Joints

4.3.5.4 Several design measures may be adopted to minimise the deleterious effectof water penetrating through the joints.

4.3.5.5 Fig. 4.3.5.F1 shows a typical arrangement at an abutment movement jointwhich shall, unless otherwise agreed by the Corporation, be adopted to avoidsome of the problems caused by leakage and to provide access for inspectionand maintenance. The abutment curtain wall is set back and the abutmentshelf dropped as necessary to provide sufficient access at the back of thedeck for inspection and maintenance. Short reinforced concrete corbelscantilevering from the deck and the curtain wall shall be provided to containthe movement joint. The deck waterproofing membrane shall be carrieddown the vertical/inclined edges of this joint and tucked into a drip grooveformed under the corbel, providing rundown protection. The inclined edges

allow hand access to the joint and assist in attaching or maintaining themembrane.

4.3.5.6 The abutment movement joint corbels soffit and the deck vertical edge shallbe treated with a 2 coat 2 mm thick polymer modified cementitiouswaterproofing material to protect the prestressing anchorage recess. Similar waterproofing treatment shall be applied on all internal surfaces of theabutment gallery including the curtain wall, cheek walls and bearing shelf. Afall of at least 1 in 40 shall be provided to a substantial drain at the back of theabutment to prevent any rundown on the abutment face.

4.3.5.7 Structural Movement Joints (SMJ) above intermediate piers shall not include

the inspection gallery. However, the joint must be accessible from within thedeck voids for inspection purposes. Intermediate piers beneath SMJ shall bedetailed such that the top surface of the pier shall be laid to fall towards thedrainage hopper. Bearings shall be seated on reinforced concrete plinths andthe top surface of the pier and the bearing plinths shall be treated with a 2coat 2mm thick polymer-modified cementitious waterproofing material.Similarly, all piers incorporating deck-drainage down pipes shall be laid tofalls and waterproofed as described above.

4.3.5.8 A drip groove, at least 25 mm deep and 25 mm wide, shall be provided at allSMJ in the superstructure soffit between the throat of the joint and the bearingtop plate to prevent any moisture migration across the deck soffit, care in

detailing shall be taken to ensure full concrete cover is maintained at the drip.





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Moisture migration might occur due to the failure of the drainagearrangements or excessive condensation within the access chamber.

Access to Bridge Voids

4.3.5.9 Access shall be provided into all structure voids whether in bridges, buildingstructures, superstructures or substructures to the approval of the Corporationin accordance with Subsection 4.2.

4.3.5.10 In addition to the requirements in Subsection 4.2., there shall be access holesin each bridge span from the top slab and continuous access from abutmentgalleries along the deck within the voids, unless it can be shown to beimpracticable. If this level of access is shown to be impracticable, thenalternative access arrangements shall be proposed for the approval of theCorporation. Voids shall be provided with a permanent lighting and electricitysupply for use during inspection and maintenance.

4.3.5.11 Covers shall be water-tight, lockable with a security key whilst maintaining theminimum clear opening specified above. Each opening shall be installed suchthat the opening is at least 100 mm above the adjacent concrete level, theactual level may be constrained by the trackform design.

4.3.5.12 Where access holes are required directly beneath the trackform, liaison withthe trackform Designer shall be carried out. The underground openings shallnot be located beneath a turnout slab or areas of floating trackform. Thetrackform Designers will specify the covers. However, the superstructuredesigner shall specify a temporary cover which shall prevent ingress of water and shall also be robust enough to prevent personnel and materials from

falling into the void.

4.3.5.13 Where access holes are outside the trackform, the superstructure Designer shall specify the covers.

Precast Segmental Bridge Construction

4.3.5.14 To prevent water penetrating the joints between segments a liquid appliedpolymer waterproofing membrane shall be applied across the joints and to thedeck surface extending at least 250 mm on both sides of each joint.

External (Unbonded) Tendons in Bridges

4.3.5.15 In view of the problems which can be caused by the corrosion of tendons, thedesign of prestressed concrete bridge decks which use external (unbonded)tendons shall allow for the tendons to be fully accessible for inspection,maintenance and replacement. The design shall allow for all these threeoperations to be carried out without affecting the safety of the structures, inaddition if practicable design shall allow these operations to be carried outwithout causing disruption to railway operations either. Consideration shall begiven to individual strand replacement systems.

4.3.5.16 Bridges designed to these principles shall be of box or beam and slabconstruction using external prestressing tendons located between the webs.





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The tendons shall typically be deflected or anchored at the soffits of crossbeam diaphragms and the tops of pier diaphragms beneath the deck slab.

4.3.5.17 If the anchorage of non-grouted tendons should fail, the completeprestressing effect and any ultimate strength is lost. This is not the case with

bonded tendons. Therefore consideration to the provision of tendonredundancy in respect of this concern shall be given in tendon design.

4.3.5.18 The corrosion protection system to external tendons shall adopt best currentpractice and be subject to the approval of the Corporation. The protectionshall consist of a multi-layered system of sheaths and corrosion inhibitingfillers. The external sheath shall be non-metallic and provide robust abrasionprotection, impact protection and UV protection if exposed to daylight.

4.3.5.19 External prestressing is not covered by the current issue of BS 5400, Part 4.Where it is considered that external tendon methods would offer substantialwhole-life cost-benefits, full details shall be submitted of methods and designstandards to be adopted to the Corporation for its Approval, beforeproceeding with the detailed design. Unless otherwise approved by theCorporation, the requirements of the UK Highways Agency BD 58/94: “TheDesign of Bridges and Concrete Structures with External and UnbondedPrestressing”, shall be adopted.

Stability of Single Track Bridges

4.3.5.20 The use of holding-down or stability bars shall not be used as a method of ensuring bridge deck stability, unless it can be shown to the satisfaction of theCorporation that there is no other feasible alternative.

4.3.5.21 If the use of stability bars is accepted, all components shall be dimensionedand located such that the full range of viaduct movement can beaccommodated without overstressing. The ducts which have stability barsshall be fabricated from grease tight stainless steel grade 316S33 to BS 970or EN Grade 1.4436 and provided with grease-tight plugs. The design and/or tender and/or contract documents as appropriate shall indicate a maximumlevel for the grease to prevent overtopping of the end due to thermalexpansion. Access shall be provided for inspection, maintenance andreplacement of the stability bars.

Bearings

4.3.5.22 The general provisions of Chapter 9 of the HKSDM shall apply to bearings for all railway and highway bridges, pedestrian bridges and other structures, asappropriate. In addition, it shall be ensured that bearings have adequateallowance for the full range of bridge or viaduct movements. The drawingsshall include full details regarding the presetting of bearings to take account of the average ambient temperature at the time of installation and allowances for shrinkage, creep, application of prestress (if any) and rotation due to live load.Screens to conceal the bearings shall not be used. The design shall allowbearings to be inspected, maintained and replaced in a safe manner, andwhere possible drawings shall indicate the intended jacking position for bearing replacement.





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4.3.5.23 Whenever possible elastomeric bearings shall be specified. However, allspecified bearings must be suitable for the applied loads and compatible withthe structures articulation and movement limits.

4.3.5.24 Where elastomeric bearings are proven to be unsuitable and mechanical

bearings are specified, bearings and guides shall be fixed at the top andbottom by bolts. Where possible, bearings shall be fixed in such a manner asto facilitate removal. The use of permanent seating plates cast or bolted tothe concrete structure is preferred. Refer to Subsection 4.2 for bearing straycurrent mitigation requirements. For precast bridge deck where upper plinthsare used between the bearing top plate and the deck, the horizontal forcesshall be resisted by a positive fixing into the structure and not by friction.

4.3.5.25 The possibility of bearing uplift shall be avoided wherever possible. However,if this proves to be unavoidable and is demonstrated to be as such to theCorporation, then notwithstanding the requirements of BS 5400, Section 9.1,the following criteria shall apply:

i) Bearings capable of resisting uplift forces

The bearing schedule shall clearly indicate uplift design load effects atSLS and ULS.

ii) Bearings not capable of resisting uplift forces

At SLS uplift is not permitted. At ULS uplift is permitted provided thatthe following is complied with:

a) the bearings are designed to allow uplift to occur;

b) the uplift of a bearing from its mountings, or separation of thebearing component parts, must not be such that they do notreturn to their designed positions for SLS loading; and

c) the loss of support due to the unloading of a bearing isconsidered in the ULS design of other structural elements.

4.3.5.26 Where rails are continuous over discontinuities in the support to the track, thebridge structure (bridge deck, bearings and substructure) and the track jointlyresist the longitudinal forces due to traction, braking or thermal effects. The

effects resulting from the combined response of the bridge structure and thetrack shall be taken into account for the design of the bridge structure,bearings, the substructure and for checking load effects in the rails.

4.3.5.27 The combined response of the bridge structure and the track shall beassessed in accordance with the loading provisions in Clause 6.5.4 of BS EN1991-2:2003 (Traffic Loads on Bridges).





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4.3.6 Structural Movement Joints

General

4.3.6.1 This subsection sets out the specific requirements for the Design of Structural

Movement Joints (SMJ) for external below ground, overhead or ground levelstructures.

External Structural Elements Below Ground

4.3.6.2 All cast in situ concrete underground structures shall be without SMJ to limitpossible ingress of water. Where this is not practicable particular attentionshall be paid to SMJ in external walls, bases, and roof slabs below groundwith respect to their watertightness and durability.

4.3.6.3 SMJ shall have a heavy duty external and internal water bar. Where shear capacity across the joint is required to resist loads and/or movements it shallgenerally be provided by dowels, shear dowels shall in all cases be aproprietary stainless steel product in accordance with grade 316S33 or 1.4436 (see BS EN 10088) . They shall be designed and fabricated so thatboth loads and movements can be accommodated in the orientationsassumed in the design. However where shear movement across the joint iscritical such as in slabs which support trackform, shear connection shalladditionally be provided by a concrete key.

4.3.6.4 The movements shall be identified and a schedule submitted of predictedmovements in accordance with Fig. 4.3.6.F1, for the approval of theCorporation.

4.3.6.5 SMJ in Immersed Tube Tunnels shall receive special consideration.Particular reference shall be made to the requirements of Subsection 4.3.4.

Overhead and Ground Level Structures

4.3.6.6 Generally the number of SMJ shall be kept to an absolute minimum within theconstraints defined in the NWDSM and those appropriate to the specificstructure under consideration, i.e. above ground structures shall have amaximum length of structure between movement joints within the movement joint limitations.

4.3.6.7 Wherever practicable, SMJ shall be watertight proprietary systems. Theyshall be designed to withstand the applied loads and accommodate all theanticipated movements of the structure without developing unacceptablestresses within the joint or in other parts of the adjacent structure.

4.3.6.8 Where the SMJ is in a visibly sensitive area or subject topedestrian/maintenance traffic, it shall be protected by an appropriatestainless steel cover plate. It shall also be ensured that the SMJ cover platesdo not present a hazard to pedestrians or other users.

4.3.6.9 All SMJ, even if designed to be watertight, shall be assumed to leak.Therefore, all SMJ should be detailed such that:





4.3/30

Table 4.3.6.T1 SMJ Movement Limits

Movement Range

Longitudinal (parallel to rails) 150 mm *

Transverse (perpendicular to rails) 2 mmVertical 2 mm

Horizontal rotation (plan) 0.003 rads

Vertical rotation (elevation) 0.003 rads

Axial rotation (twist) 0.001 rads

4.3.6.14 Reference shall be made to the permanent way alignment design to ensurethat there are no SMJ positioned beneath turnout slabs or horizontal curves of radii less than 750 m.

4.3.6.15 The movements shall be identified and a schedule shall be submitted of predicted movements to the Corporation for approval in accordance with Fig.

4.3.6.F1.



Section 4: Civil Engineering D/MTRC/NW/DSM/4.3 Specific Design Criteria

ST/403/A5


4.3/31



4.4/2

Section 4: Civil Engineering D/MTRC/NW/DSM/ST/404/A54.4 Design Loads


i) dead load ± earthquakeii) dead load + imposed load ± earthquakeiii) dead load + temperature

iv) dead load + imposed load + temperature

4.4.2.5 Total and differential movement, shrinkage, creep, differential water head,differential building surcharge shall be combined with items i) to iv) Cl.4.4.2.4, if applicable.

4.4.2.6 For the additional load combinations in Cl.4.4.2.4, the partial load factors to beadopted in the design shall be taken from the HKSDM or below for other designcodes, as appropriate:

Dead Gk = 1.2 (0.9)Imposed Qk = 1.3

Temperature Tk = 1.3Earthquake Ek = 1.4

4.4.2.7 Adverse or beneficial factors (bracketed) in Cl. 4.4.2.6 shall be used dependingwhich gives the more onerous condition for the element under consideration.

Addi tional Load Combinations for Immersed Tube Tunnels

4.4.2.8 “Hong Kong Code of Practice for the Structural Use of Concrete” does not fullyspecify the load factors and loading combinations for IMT structures. Accountshall be taken of the method and sequence of construction in developing the

design loads for the structure. In the permanent condition at ultimate limitstate, the load factors and combination requirements of Table 4.4.2.T1 shall atleast be assumed in addition to other combinations that are consideredrelevant. The combination of material densities and seawater densities andlevels for each particular loading condition shall be allowed for. The minimumload factor value shall be used when the loading is relieving or beneficial.



4.4/3



Table 4.4.2.T1 Load Factors and Combinations

CombinationLoading

(a) (b) (c)

Dead Loads 1.4/0.9 1.2/0.9 1.05

Live Loads 1.4/0.0 1.2/0.0 -

Water Pressure 1.4/0.9 1.2/0.9 1.05

Vertical Earth Pressure 1.4/0.9 1.2/0.9 1.05

Lateral Earth Pressure 1.6/0.9 1.4/0.9 1.05

Differential Settlement 1.2/0.0 1.2/0.0 1.05

Loss of Support 1.2/0.0 1.2/0.0 1.05

Temperature 1.3/0.0 1.2/0.0 1.05

Seismic - 1.2/0.0 1.05

Anchor Impact/Sunken ship * - 1.2/0.0 1.05

Flooding + - 1.05/0.0 1.05

Notes * Anchor impact and sunken ship loads need not beconsidered concurrently.

+ Flooding need not be considered concurrently with

seismic and anchor impact/sunken ship in combination(b).

4.4.3 DEAD LOADS

General

4.4.3.1 Dead loads and superimposed dead loads such as finishes, blockwork walls,cladding and false ceilings, shall be calculated in accordance with Code of Practice for Dead and Imposed Loads or from the unit weights given in Code of Practice for Dead and Imposed Loads or from the actual known weights of the

materials used. Reference shall be made to the Room Data Sheets in Section 5and Section 8 of the NWDSM for details of specific superimposed loads inparticular locations and special finishes.

4.4.3.2 Unless otherwise stated, the unit weight of concrete used in or the design shallbe in accordance with Table 4.4.3.T1.



4.4/4



Table 4.4.3.T1 Unit Weights of Concrete

Description Unit weight (kN/m3)

Reinforced concrete 24.5

Plain concrete 23.6

Lightweight mass concrete 21.5

Railway Engineering Dead Loads

4.4.3.3 Allowances shall be made for ballasted, floating or rigid trackforms asappropriate according to the design of the trackwork. Typical dead load unit

weights for railway engineering components and trackforms are given inSection 3 of the NWDSM.

4.4.4 IMPOSED LOADS

Floor Loads

4.4.4.1 Structural floor and roof members shall be designed to resist the distributed or concentrated loads given in Table 4.4.4.T1 and Table 4.4.4.T2. Theconcentrated load shall be positioned such that it gives the most onerousloading condition for the element under consideration. The design of plant

room floors shall also be checked for the dead loads of electrical andmechanical equipment given in Table 4.4.5.T1, positioned to give the mostonerous condition.

Table 4.4.4.T1 Floor Imposed Loads

Location of Floor Distributed Load(kN/m2)

Concentrated Load(on a square of 300 mm side)

(kN)

Concourses and PlatformsOfficesToilets

Staff Rooms

6 5

Store Rooms 10 10

Plant Rooms other thanSubstations, Transformer Rooms and Chiller Rooms

10 10

Substations 20 20



4.4/5



Rectifier/Transformer Rooms

Switch Gear Plant Room

20

7.5

Equipment loads to

be determined inaccordance withTable 4.4.5.T1.

20

10

Chiller Rooms 10 15

Fire Tank Room Designer to determine based on the water holding capacity of the tanks

Sewage Ejector Tank Room Designer to determine based on the water holding capacity of the tanks

Table 4.4.4.T2 Roof Imposed Loads

Location of Roof

Distributed Load(kN/m2)

Concentrated Load(on a square of 300

mm side)(kN)

1. Without direct access 1.0 2.0

2. With access only tomaintenance personnel

1.5 2.0

3. With direct access bypublic 5.0 2.0

4. Landscaped areas 7.5 9.0

Note: 1) For floor or roof highway and railway imposed loading seeSubsection 4.4.7

4.4.4.2 In addition, building structures shall be designed for an imposed dead load fromservices fixed to the underside of supported areas (supported area is the planarea of structure supported by the structural element under consideration) asgiven below:

Supported Areas Uniform LoadUp to 10 m² 2.0 kN/m²Between 10 and 30 m² 1.5 kN/m²Greater than 30 m² 1.0 kN/m²

4.4.4.3 A nominal imposed load of 0.1 kN/m² shall be allowed for the design of all falseceilings.



4.4/6



4.4.5 E&M LOADS

Equipment Loads

4.4.5.1 Typical unit weights for E&M trackside cabling, cable troughs, sunshields, firemains and overhead line (OHL) shall be allowed in accordance with Section 7of the NWDSM.

4.4.5.2 Indicative dead loads of typical Electrical and Mechanical (E&M) plant are givenin Table 4.4.5.T1. The values to be used in designs and the footprint of equipment shall be confirmed before detailed design commences.

Table 4.4.5.T1 E&M Loads

Area Room Designation Main E&M Plant Load (kN)

TractionSubstation

33 kV Switchgear Room

33 kV Control Room

DC Switchgear Room

Rectifier Room

Rectifier Transformer Room

33 kV Switchboard

Control Panel

DC Switchboard

Rectifier

33 kV/586 VRectifier

Transformer

300 (static)350 (dynamic)

40

60 (static)60 (dynamic)

60

250

StationSubstation

11 kV Switchgear Room

LV Switchgear Room

3.3 kV Switchgear Room

Station SubstationTransformer Room

(RMU) 11 kVSwitchboard

415 VSwitchboard

3.3 kV Switchboard

3.3 kV/415 VTransformer

20

15

65

60

DistributionSubstation

DistributionTransformer Room

33/11 kVTransformer

33/3.3 kVTransformer

300

100

VentilationBuilding

Standby Generator Room

Infeed Transformer Room

Diesel Generator

132/33 kVTransformer

150

600

Telecomms/ Signalling

Signalling EquipmentRoom

Power Supply Unit 15 (applicableto all)



4.4/7



Area Room Designation Main E&M Plant Load (kN)

TelecommsEquipment Room

Telecomms BatteryRoom

ECS ECS Plant Room AHU FansIntake Air FansReturn Air FansChillersPumps

30151575-100 kN20

4.4.5.3 Notwithstanding the requirements of Cl. 4.4.5.1 and Cl. 4.4.5.2 and the typicalE&M loads given in Table 4.4.5.T1, the floors and supporting structuralmembers in substations, switch rooms, plant rooms or other places containing

switch gear or machinery shall be designed to resist without distress or damagethe following loads:

i) the full net dead load of an assembled piece of equipment at anyreasonable position on the structure likely to be experienced during or after installation;

ii) dynamic effects due to the operation of equipment in its design mode;and

iii) hoisting loads for assembly and maintenance of the equipment.

4.4.5.4 Items of equipment with dynamic load characteristics and contained within thesame sub-structure shall be assumed to exert their loads simultaneouslyexcept that when the number of items exceeds four, the dynamic factor shall bereduced by one unit. Cases i) and ii) in Cl. 4.4.5.3 shall be assumed to operatesimultaneously.

Escalator Loads

4.4.5.5 For preliminary design purposes Section 11 of NWDSM gives the dead plusimposed loads acting on the base plinths. The loads are uniformly distributedacross the escalator supports and typical arrangements. The loads listed arebased on an assumed type of escalator and will vary from one manufacturer to

another. For detailed design purposes, loadings shall be adopted that arecompatible with the actual type of escalator being specified.

4.4.5.6 Hoisting hooks shall be provided at selected positions to enable escalators tobe lifted into position, these shall be checked during the detailed design againstthe escalator types being specified. The allowable hoisting loads shall bespecified in the general arrangement drawings.



4.4/8



4.4.6 RAILWAY LIVE LOADS

General

4.4.6.1 In the design of railway structures, the nominal primary and associatedsecondary railway live loads shall be in accordance with BS5400, Part 2,Section 8, except that the nominal type RU and RL loading shall be replaced bythe primary railway live loads given in Cl. 4.4.6.3.

4.4.6.2 All other secondary railway live loads shall be calculated in accordance with theprovisions for type RL loading given in BS5400, Part 2, Section 8. These loadsshall be applied to all structures unless indicated otherwise in Cl.4.4.6.4 to4.4.6.17.

Primary Railway Live Loads

4.4.6.3 The standard design loading for railway vehicles of various line shall be themost onerous in Fig. 4.4.6.F1. This loading shall be applied to each and everytrack. The most onerous effect on the railway structures shall be determined byapplying the loading at any point along the track.

Design loading due to XRL vehicles is set out in the XRL Design Standardsmanual.

Associated Secondary Railway Live Loads

Fatigue Loads

4.4.6.4 Allowance for fatigue loading in accordance with the provisions of HKSDMChapter 10 shall be made in all structures which support railway, highway or other significant cyclical loading.

Dynamic Loads

4.4.6.5 The dynamic load factors for railway vehicles given in Cl. 8.2.3.2 of BS5400,Part 2, for type RL loading shall be used in the design of all structures except inthe following circumstances:

i) for design of trackform (see Section 3 of the NWDSM);

ii) for structures with eccentric track support structures, including bridgescarrying tracks on cantilever slabs;

iii) for steel and composite steel and concrete superstructures; and

iv) for structures with spans of 100 m or greater.

4.4.6.6 In the case of items (ii), (iii), or (iv) of Cl. 4.4.6.7, detailed analyses, design andreporting of the dynamic effects of the structure shall be undertaken inaccordance with Subsection 4.8 Dynamic Analysis requirements. In all casesstructural forms particularly sensitive to cyclic dynamic railway loads shall be

avoided. Where this is not possible, the elements fitness for purpose shall bedemonstrated by carrying out analyses in accordance with Subsection 4.8.



4.4/9



4.4.6.7 For underground structure design only the dynamic load factors given in Cl.8.2.3.2 of BS5400, Part 2, shall be replaced by the following:

i) For spans along the lengths of the track, whether simply supported or continuous:

Spans of 3 m or less, dynamic factor 1.55Spans of 10 m or more, dynamic factor 1.20

For spans between 3 m and 10 m, the dynamic factor shall becalculated as follows:

I = 1.55 - 0.05 (x-3)

I is the dynamic factor

x is the span length.

ii) For spans at right angles to the direction of the track, whether simplysupported or continuous, the dynamic factor shall be 1.40.

4.4.6.8 For all structures it shall be ensured and checked that structure dynamicresponse when considered in conjunction with the trackform response iscompatible with the achievement of the design standard requirements for 'RideQuality' given in Section 3 of the NWDSM. The trackform response shall bebased on an assessment of the specific trackform type for the location beingconsidered.

Lurching Loads

4.4.6.9 Lurching loads from railway vehicles shall be applied in accordance withBS5400, Part 2, Section 8. The track or tracks selected shall be those in whichthe transfer of load has the greatest effect on the element under consideration.

Centrifugal Loads

4.4.6.10 The equation for the nominal centrifugal load for railway vehicles given in Cl.8.2.9 of BS5400, Part 2, may be simplified to:

Fc = 3811 kN/mR

Where R = radius of the curve, provided the loaded length of the element beingconsidered is less than 2.88 m and the greatest speed envisaged on the curvein question is less than 120 km/h.

4.4.6.11 In all other cases the nominal centrifugal load shall be calculated using the fullequation in Cl. 8.2.9 of BS5400, Part 2 with a value of P = 40 kN/m.

Traction and Braking Loads

4.4.6.12 Traction - all axles of a train shall be considered as driven axles and the total

traction force shall be equivalent to 30% of the maximum standard axle loads,subject to a maximum of 600 kN.



4.4/10



4.4.6.13 Braking - all wheels of a train shall be considered as braked and the totalbraking force shall be equivalent to 25% of the maximum normal axle loads,subject to a maximum of 800 kN.

4.4.6.14 Where the length of the structure under consideration is greater than a trainlength, the total traction and braking forces to be applied shall be thatequivalent to one train. In the case where the length of structure considered isless than the length of a train, then as many axles as possible shall beconsidered as acting on that length.

Derailment Loads

4.4.6.15 Derailment loads shall be derived in accordance with BS5400, Part 2, Cl. 8.5,with the exception that condition (c) shall not apply to underground structures.For bridges the clause shall be reworded as follows:

i) For overturning or instability checks, four EMU Train or Works Trainbogies, whichever is more onerous, (with axle centres as defined inCl.4.4.6.3) shall be considered to have come to rest with the four Trainbogies centre of gravity located on the line of the inside face of theparapet, whilst the remaining Train bogies centre of gravity lie not morethan 0.25 m from the track centre line. Under this loading the structureas a whole shall not overturn and the superstructure shall not lift off thebearings. However, it may be assumed that local damage may occur.(See Fig. 4.4.6.F2 for details.)

ii) The parapets to railway bridges shall not be designed to withstand theeffect of impact from a derailed train.

4.4.6.16 Local damage means, at worst, the loss of a parapet and/or an enclosure unit.The structure on which the train runs shall be capable of being rapidly broughtback into full use after minimal repairs. For a structure carrying double tracks,the derailment of a train on one track shall not restrict the operation of trains onthe other track, except in the case of physical obstruction.

4.4.6.17 Design loads shall be applied in accordance with BS5400, Part 2, Cl. 8.5.2except; in (a)(2) the vertical load shall be amended to 100 kN; in (b) each of theconcentrated loads shall be 130 kN and in (c) the length of the line load shall be

limited to 25 m.

4.4.7 HIGHWAY LIVE LOADS

4.4.7.1 Highway structures and pedestrian bridges shall be designed to resist the liveloading and fatigue loading given in the HKSDM. The level of abnormal or HBloading for each particular highway structure shall be agreed with the HighwaysDepartment.

4.4.7.2 For underground structures beneath an existing or proposed highway, thestructure shall be designed to resist the load defined in Cl.4.4.7.1. Where there

is 2 m or more cover to the elements under consideration, these loads may berepresented by the following:



4.4/11



Type HA Loading = 12 kN/m²45 units HB Loading = 24 kN/m²

4.4.7.3 Structures adjacent to highways which support vehicle and/or pedestrianparapets shall be designed in accordance with the requirements of HKSDM.Particular attention shall be paid to the effects of parapet horizontal vehiclecollision loading and concurrent vehicle vertical accidental wheel loadingadjacent to the parapet, in accordance with Subsection 2.8 of the HKSDM.

4.4.8 SOIL AND WATER LOADS

Soils Criteria

4.4.8.1 For the calculation of the weight of backfill, in the absence of site specific tests

or data, the bulk unit weights of 20 kN/m3 shall be used. Where more onerousfor the element being considered, allowance for the effects of horizontalcompaction loads shall be made in the lateral soil coefficient adopted inaccordance with Subsection 4.6.

4.4.8.2 Lateral loads on underground structures shall be derived from maximumsaturated bulk density or submerged density as applicable and the effectiveangle of shearing resistance (Ø') using the methods defined in Subsection 4.6for each soil stratum

Groundwater Criteria

4.4.8.3 For the calculation of groundwater pressures and flotation, a groundwater unitweight of 10 kN/m3 shall be assumed. All groundwater levels used in the designof permanent works shall be determined following a review of the siteinvestigation data relevant to each specific element of the works.

Differential Water Levels Across Structures

4.4.8.4 All underground structures shall be designed to resist a difference ingroundwater table level between opposite sides of the completed structure. Inthe absence of detailed information, a minimum difference in groundwater leveltable of 5 m shall be used. This exceptional or temporary loadcase is

considered to represent a 'burst water pipe' or 'groundwater flow' differentialloading condition. The actual site conditions shall be considered and wherealternative water level differences are considered appropriate they shall beproposed in the AIP and subject to the approval of the Corporation.

Temporary and Permanent Structures in Soil

4.4.8.5 Lateral loads on underground structures shall be derived from maximumsaturated bulk density or submerged density as applicable and the effectiveangle of shearing resistance (Ø') using the methods defined in Subsection 4.6

for each soil stratum.



4.4/12



4.4.8.6 Distinction shall be drawn between drained and undrained strengths for temporary and permanent designs. The appropriate water pressures shall beapplied.

4.4.8.7 In the absence of more accurate calculation methods, the completedPermanent Works shall be designed to resist the loads resulting from earthpressure 'at rest'. The effects of compaction of backfill and the lateral stiffnessof the structure shall be included and considered in the selection of the 'at rest'coefficient of lateral pressure. 'At rest' or 'active' coefficients of earth pressureused to calculate ground loads shall be derived in accordance with Subsection4.6.

Negative Skin Friction

4.4.8.8 Deep foundations and other structural elements which are constructed in newlyreclaimed areas will be subject to negative skin friction (NSF) loads caused by

settlement of the fill and underlying soft material. NSF shall be considered as apermanent load on the structural elements and shall be determined from thesettlement profile of the relevant strata in accordance with Subsection 4.6.

4.4.8.9 Bitumen, other slip coats or liners applied to structural elements to minimisenegative skin friction or other adverse soil conditions may be consideredtogether with appropriate reduction factors.

Existing Buildings and Future Development Loads

4.4.8.10 To allow for existing buildings or the possibility of future developments being

constructed next to underground railway structures, additional vertical andhorizontal soil pressures shall be considered in all permanent loadcombinations. In the absence of site specific data, the pressure shall be 20kPa acting horizontally on any one side of the basement wall over the entiredepth from the ground to the bottom of the base slab. Loads shall be applied incombination or individually, whichever is more onerous for the element beingconsidered.

4.4.8.11 For all underground structures in areas not designated for development or future highway construction, a minimum vertical live loading over the structureof 20 kN/m² shall be assumed in addition to other loading applied.

Highway Surcharges

4.4.8.12 Imposed loads directly borne by the soil behind the retaining structures or slopes shall be allowed in the design. In the absence of more exactcalculations, the nominal surcharge loads due to highway loading shall be inaccordance with Table 4.4.8.T1.



4.4/13



Table 4.4.8.T1 Surcharge Loads for Retaining Structures or Slopes

Road Class Type of Live LoadingEquivalentSurcharge

Urban Trunk Roads HA+45 units of HB 20kPa

Primary Roads,Construction Access

HA+371/2 units of HB 15kPa

District and Local Distributors,Other Rural Roads, AccessRoads, Carparks

HA 10kPa

Footpath, isolated from roads

Play areas - 5kPa

Hydrodynamic Loads

4.4.8.13 Hydrodynamic loads due to current or wave effects shall be considered inaccordance with BS6349 - Code of Practice for Maritime Structures and theHKPWDM on all structures where the structure is exposed to them, such asseawalls, piers, IMT's, foundation piles in rivers or waterways. In additionallowance and/or protective measures, such as suitably graded rock blankets,to resist scour around structures due to wave or current effects shall be adopted.When designing for scour particular care shall be taken to adopt suitable

current enhancement factors where turbulence due to the structure intrusion inthe current flow is predicted to occur.

4.4.9 FLOTATION LOADS

4.4.9.1 Underground structures shall generally be checked for flotation using theminimum water density given in Cl. 4.4.8.3. However, in situations where thegroundwater will be influenced by seawater, the most onerous groundwater density unit weight in the range of 9.8 kN/m3 to 10.05 kN/m3 shall be used toallow for the variation in salinity, temperature and sediments content.

4.4.9.2 The information on groundwater levels to be considered for each stage in thedesign life of the structure shall include, but shall not be limited to, the following:

i) the current and projected tidal variations in accordance with theHKPWDMl;

ii) the long-term rise in sea level which, in the absence of any detailedinformation, shall be taken as 0.5 m over the design life;

iii) the design free surface water levels due to storm, wind surge, andponding;



4.4/14



iv) the design groundwater level including the influences of rainfall, surfacewater run-off and groundwater movement;

v) the damping of seawater tide influences by intervening ground;

vi) ground permeability; and

vii) accidental influences, such as water main breakages and dewatering.

4.4.9.3 The following design groundwater levels shall be considered for flotation loads:

i) Construction

The design groundwater levels during Construction stage shall take intoaccount all events during the time-span which represents theconstruction of the Works. It shall consider all aspects of the proposed

Temporary Works and the case of an excavation over or adjacent to theWorks at a later date.

ii) Operational

The design groundwater levels during the life of the structures shall takeinto account the appropriate combinations of conditions given inCl.4.4.9.2 that may occur over the design life of the structure.

iii) Extreme

The Extreme case reflects the element of uncertainty in assessinggroundwater conditions and shall be represented by groundwater levelswhich would be considered as the 'worst credible' level for the particular location of the scheme. In the absence of supporting documentation,the minimum groundwater level to be assumed for the Extreme caseshall be 1 m below general finished ground level.

Backfill Load Constraints

4.4.9.4 The weight of the backfill above the roof slab shall be based on the bulk or saturated unit weights above and submerged unit weights above and below thewater table. The depth of the backfill shall be that appropriate to the load

combination under consideration.

4.4.9.5 Where the depth of the backfill is less than 0.5 m it shall be neglected in thecalculation of the net downward load. Where it is explicitly specified that thebackfill over the structure may be re-excavated to allow for future construction,it shall be neglected down to the proposed excavation depth in the calculationof the net downward load. This particular load case shall be considered under a construction combination.

Structural Load Constraints

4.4.9.6 For all stages and structural elements under consideration, the self-weight of

the structure shall exclude the loads from:



4.4/16



q = 1.2 kN/m². The coexisting live load shall be a static vertical load of 18 kN/m applied at the track centre line.

ii) To represent the train toppled by wind where the structure shall be

considered as 'unloaded', the train shall be considered to act as part of the structure and will increase the depth, d, with the highest part of thetrain 3.1 m above rail level. The dynamic pressure head shall be thatcalculated for the 'unloaded' condition in accordance with Cl. 4.4.10.1. A coexisting additional vertical dead load of 18 kN/m shall be applied onthe leeward rail.

4.4.10.3 Wind loads for building structures shall be in accordance with the Codes of Practice on Wind Effects, Hong Kong, published by the Buildings Department.

4.4.11 TEMPERATURE, SHRINKAGE AND CREEP LOADS

Temperature Effects

4.4.11.1 The total and differential temperature ranges given in Subsection 2.4 of theHKSDM shall apply in the design of all structures. Full account of the particular structures exposure to the stated temperature conditions shall be considered.

4.4.11.2 The detailing of expansion joints, including initial settings at installation, shalltake account of the maximum and minimum temperature data given inSubsection 2.4 of the HKSDM. Installation setting constraints shall be statedon the drawings.

4.4.11.3 Where above-ground or bridge structures are designed as a continuous rigidframe, the effects of different parts of the structure being at differenttemperatures simultaneously because of solar-heating, shading, and air-conditioning shall be taken into account.

Shrinkage and Creep Effects

4.4.11.4 The shrinkage and creep effects given in Subsection 2.5 of the HKSDM shallapply to the design of all structures.

4.4.12 COLLISION AND IMPACT LOADS

Collision Loads from Highway Vehicles

4.4.12.1 Where bridges or structures adjacent to highways are at risk from collision byroad vehicles, the requirements of Subsection 2.7 of the HKSDM shall beapplied regardless of the permitted traffic speed on the road concerned.

4.4.12.2 Columns or other supports located in the light traffic circulation areas shall bedesigned to withstand vehicle impact loadings, unless barriers to such columnsor supports are provided. The impact loading for the columns, supports, or barriers, as appropriate, shall be in accordance with the Building (Construction)

Regulations 17(4).



4.4/17



Collision Loads from Railway Vehicles

4.4.12.3 Structural elements which are at risk from collision by railway vehicles shall bedesigned in accordance with the requirements given in subsection 4.2.

Collision loads shall be considered at ultimate limit-state only using theappropriate partial load factors.

4.4.12.4 Station platforms edges shall be designed to withstand a nominal load of 1000kN acting horizontally and normal to the edge of the platform slab edge over alength of 2.2 m in conjunction with all factored permanent loads. No other railway collision loads shall be considered behind the platform edge, unlessthere is a risk of an errant railway vehicle mounting the platform or collidingwith structural elements located in the vicinity of the track. Supports on theopposite side of the track to the platform edge shall be designed in accordancewith Cl. 4.4.12.5. below.

4.4.12.5 All structural elements other than platform edges shall be designed to withstanda nominal point load of 1250 kN acting horizontally in any direction at the top of the element level, or 1.2m above the adjacent rail level, whichever is less, inconjunction with the relevant factored permanent loads only. Where the soffitof the structural element occurs between 1.2m and 4.0m above adjacent raillevel, the load shall be applied at soffit level. Some minor local damage isacceptable, although this must be repairable in non-operating hours.

4.4.12.6 Railway Bridge Over Navigation Channels

Bridge piers, separate barriers and other supports located in a river and

navigation channel shall be designed to withstand impact loadings from errantbarges and ships, unless separate barriers to such piers and supports areprovided. The design shall be in accordance with Section 4.6 of EN 1991-1-7:2006E and consult the Marine Department if required. The load factors andapplicable load combinations need to be defined.

Immersed Tube Tunnels (IMT) - Marine and IMT Imposed Loads

4.4.12.7 Marine and IMT imposed loads shall be considered at the ultimate limit stateonly and shall include, but not be limited, to the following:

a) Anchor Impact

The anchor design shall be selected as appropriate to the shippingexpected in the vicinity of the tunnel. The minimum requirement of avertical and horizontal concentrated characteristic load of 700 kN actingover an area of 1 m diameter at the level of the tunnel roof or on the wallshall be considered. The load shall be applied at any location beneaththe seabed. The effects of an anchor being dragged across the line of the tunnel shall also be considered.

b) Sunken Ship

A ship, the size of which shall be appropriate to the vessels expected in

the vicinity of the tunnel, shall be considered stranded on top of thetunnel. The minimum requirement of a vertical uniform characteristic



4.4/18



load of an effective 50 kPa, applied at the level of the tunnel roof, at anylocation beneath the seabed shall be applied. The loading shall beapplied over the full width of the tunnel and/or a width of 10 m besidethe tunnel, over a length measured along the longitudinal axis of the

tunnel of 30 m.

4.4.13 EARTHQUAKE LOADS

General

4.4.13.1 The loads and consequences of seismic activity shall be allowed for on allstructures, earthworks and infrastructure. For all structures, earthworks andinfrastructure with a design life of 120 years, a bedrock induced motionequivalent to a peak horizontal ground acceleration of 15%g and a peakvertical ground acceleration of 7.5%g shall be adopted in design. This level of

ground motion has been shown to represent approximately a 1 in 1000 year return period earthquake event in the Hong Kong region. This design eventhas therefore approximately a 10% probability of being exceeded during thedesign life of the structures, earthworks and infrastructure. (Reference"Seismic Design of Buildings in Hong Kong" by Scott, Pappin and Kwokpresented at the 'Earthquake Resisting Structures' seminar on 3rd May 1996and "Seismic Design Planning and Procedure" by Leung presented at the'Highway Structures' seminar on 7th May 1993).

4.4.13.2 Seismic forces shall be considered in combination with dead loads,superimposed dead loads, other long term loads and imposed loads, in

additional separate load combinations in accordance with the specified codesof practice and Subsection 4.4.1. Seismic forces shall be considered atUltimate Limit State only in accordance with the design and analysis methodsdescribed in Subsection 4.8.3.

4.4.13.3 Member forces and moments shall be derived from a combination, of thevertical acceleration and any two horizontal orthogonal seismic accelerations,to account for the directional uncertainty of earthquake motions and thesimultaneous occurrences of earthquake forces in the three perpendicular directions. 100% of the seismic loads derived from analysis in the onedirection, shown to be most adverse for the member under consideration, shallbe considered as concurrent with 30% of the seismic loads derived in analysis

in the other two orthogonal directions.

Estimation of Earthquake Loads

4.4.13.4 When deriving a structure horizontal seismic force the total vertical loads shallgenerally comprise the permanent vertical loads (dead and imposed) and 50%of the full live loading. However, for bridges or structural elements subject tovehicle loadings the total vertical load shall comprise the permanent verticalloads (dead and imposed) and either of the following as appropriate:

i) For structures supporting railway vehicles - a live load derived byapplying an arrangement of Maximum Standard Axle loads that when

applied to the structure produces the most adverse effect in the elementunder consideration. Single track structures shall be considered to



4.4/19



carry no more than one eight car train, whereas multiple track structuresshall be considered to carry no more than two eight car trains.

ii) For structures supporting highway vehicles - 1/3 type HA loading on

one notional lane in each direction

iii) For footbridges no live load allowance need be made.

4.4.13.5 The resulting member forces and moments due to P-delta effects (loadeccentricity due to member deformations during loading) shall be considered inall analyses. However, where the ratio of secondary moment to primarymoment is less than 0.10, P-delta effects may be ignored.

Underground Structures

4.4.13.6 As a general rule structures shall not be constructed in ground conditions with a

low factor of safety against liquefaction (<1.5). However where this is notpossible, stabilisation measures such as densification shall be adopted as wellas consideration of bulk weight compaction and horizontal pressures (i.e. Ko =1). Consideration shall be given to induced loads due to ground movementand pile buckling due to liquefaction of the supporting ground mass.

4.4.13.7 Internal members of underground structures shall be designed for a seismicload of 10% of the total mass of the member plus 10% of any live and deadloads acting directly on the member at that level. The seismic force shall beconsidered to act concurrently with the dead and live load in any direction inorder to produce the most severe effect on the member.

Fixtures and Fittings

4.4.13.8 All frames and mountings for electrical and mechanical equipment (withsubstantial mass), including but not limited to transformers, switchboards,batteries, UPS systems, air dampers, fan coil units, split type air-conditioners,ventilation fans and air handling units, shall be designed in accordance with thefollowing criteria:

i) All anchor bolts shall be designed to withstand an unfactored lateralforce equivalent to 15% of the mass of the supported equipment.

ii) All frames, baseplates, anchor bolts, etc. shall be designed inaccordance with the relevant structural design standards, with aminimum factor of safety of three, without loss of function.

iii) The anchor bolts shall be not less than 10mm diameter.

iv) Cross bracing shall be provided as necessary to ensure lateral loadingcan be transmitted to the supports without any excessive distortion.

Light weight metal air ducts, pipes, cable trays and trunking shall be excludedfrom this requirement.



4.4/20



4.4.14 PARAPET LOADS

General

4.4.14.1 Parapets to bridges shall be designed and detailed in accordance with Section15 of the HKSDM, and Cl.4.4.13.2 to Cl.4.4.13.5 inclusive, and the followingrequirements:

i) The design of parapets shall be based on cantilever action from thebridge deck. Main structural members shall not be designed as vehicleor vehicle/pedestrian parapets.

ii) The voids between the parallel decks of divided highway structures over railway tracks shall be protected by type 4 high containment parapets or covered with a slab designed to carry HA loading.

Wind

4.4.14.2 A characteristic dynamic pressure head, in accordance with Cl. 4.4.10.1 for unloaded structures, shall be considered as acting on the exposed parapetfaces in either direction. The degree of exposure assumed shall be proposedin the Design Statement and subject to the approval of the Corporation.

Electric Cables Mounted on Parapets

4.4.14.3 The cables mounted on parapets shall be regarded as a superimposed deadload and shall be applied only to parapets on bridges carrying railways. The

maximum cable loading including supports per parapet shall be in accordancewith Section 7 stated values for trackside cabling.

Derailment

4.4.14.4 The parapets to railway bridges shall not be designed to withstand the effectsof impact from a derailed train.

4.4.15 CROWD LOADS

4.4.15.1 For the restriction and control of the movement of people, crowd loads on wall,

parapets or barriers in accordance with Table 4.4.15.T1 shall be adopted for the design where applicable. The crowd load and the wind load shall beapplied seperately for whichever is more onerous.



4.4/21



Table 4.4.15.T1 Crowd Loads

Usage

UDL Applied

at a Height of 1.1m AboveFinished Floor

Level

kN/m run

UDL Applied

on the InfillBetween Floor and Top Rail

kN/m2

Concentrated

Load Appliedon any Part of the Infill

between Floor and Top Rail

kN

PedestrianBarriersSubject toCrowd load

3.0 1.5 1.5

Parapets atEdge of Void or Change in Floor Level

3.0 1.5 1.5

Others 0.75 1.0 0.5

Note: 1) Table 4.4.15.T1 loads need not be considered concurrently

A horizontal load of 3.0 kN/m length shall be applied at the highest point of all

parapets, other than those described in Table 4.4.15.T1, in any directionwhichever is most onerous on pedestrian, highway and railway structures.

4.4.15.2 Passengers can be adversely affected by the dynamic behaviour of thestructures and crowds may cause dynamic effects in the structure. To avoidadverse vibrations, the natural frequencies of sensitive structures shall bereviewed in according with Section 2.12.3 of HKSDM and NA to BS EN1991-1-2:2002.

4.4.16 AIR PRESSURE

4.4.16.1 A minimum nominal air pressure of ±0.5kN/m2 shall be allowed for the designof all interior walls.

4.4.16.2 Walls in areas subject to large changes in air pressure shall be designed to

withstand a nominal load of not less than ±1.5 kN/m2 or the characteristic air pressure for the designated usage of the area, whichever is more onerous.The areas subject to large changes in air pressure include, but not limit to,vent shaft, plenums, ECS rooms, fan rooms, track sides and station ends.

4.4.16.3 For dividing walls between two adjoining tunnels the worst case of maximum+ve pressure on one side and maximum -ve pressure from the other sideshall be taken as the design case.



4.4/22



4.4.16.4 For the purpose of wall design, air pressure and wind load shall not be actingconcurrently on the structure.

4.4.16.5 Ceilings in concourse and station entrance subject to large changes in air

pressure shall be designed to withstand a nominal load of ±1.2 kN/m2 or asdetermined by the Code of Practice on Wind Effects Hong Kong, whichever ismore onerous.

4.4.16.6 Aerodynamic forces from passing trains in open areas shall be taken intoaccount when designing noise barriers and platform gates adjacent to railwaytracks.

4.4.16.7 Design loads shall be applied in accordance with Clause 6.6 of BS EN 1991-2:2003 (Traffic Loads on Bridges)

4.4.17 CONSTRUCTION LOADS

4.4.17.1 Where structures forming part of the works are subject to loading from mobileconstruction plant which is essential to the method of construction envisaged(including construction of trackform), they shall be checked and designed for the effects of such loading at each stage of the assumed constructionsequence. These assumed loads shall be agreed with the Corporation andclearly indicated on the relevant drawings.



4.4/24



Figure 4.4.5.F2

Not Used





4.4/26




4.5 Site Investigation


4.5/1

4.5 SITE INVESTIGATION

4.5.1 SCOPE

4.5.1.1 This subsection outlines the requirements for site investigation to be carried outfor all civil engineering and building works. It does not include site investigationfor controlling or monitoring specific construction processes during their

execution, which are an integral part of quality assurance for that process.

4.5.2 DEFINITIONS

4.5.2.1 For the purposes of this subsection the following definitions shall apply:

i) Site investigation is the comprehensive assessment of a site includingpast use, environmental constraints, topographic and hydrographicsurvey, including aerial photographs; location of services and utilities, in

addition to establishing the fundamental geological and geotechnicalcharacteristics. Such an assessment encompasses the appraisal of both existing data and data established during the course of field andlaboratory investigations. In its widest context the term “Site

Investigation” includes ground investigation. Site investigation willcomprise desk-top study of existing maps, all existing information on thesite, aerial and ground photographs; and fieldwork which will include siteinspection with various surveys and further photographs taken of theSite and adjacent features and structures.

ii) Ground investigation is the exploratory investigation using direct and/or indirect techniques to determine the structure and characteristics of anyground that may be influenced by a development. The collectedinformation is used to establish or predict ground and groundwater

behaviour during and subsequent to construction. Ground investigationworks should only proceed once all of the existing information and agood understanding of the site and general knowledge of the groundconditions have been obtained.

iii) Observational Method is a continuous, managed, integrated process in

ground engineering with the objective of achieving greater overalleconomy without compromising safety. Within formally agreedorganizational objectives and formally assigned responsibilities designand planning, construction control and monitoring and review andimplementation of pre-planned contingency measures are integratedwithin an auditable process.






4.5/2

4.5.3 GENERAL

4.5.3.1 Many of the construction risks are related to site conditions. Site investigation isan important part of the risk management of Corporation projects. It shall be

planned and executed so that uncertainties are identified, quantified in terms of threats and opportunities and managed throughout the design and constructionphases of a project, so as to achieve convergence between estimated costsand out-turn costs. The planning of each phase of site investigation to meetstated objectives shall be agreed with the Corporation before work commences.

4.5.3.2 The designer shall propose measures whereby he is to be advised of thoseground conditions encountered during construction which he deems essential tocompare with those assumed as a result of site investigation.

4.5.3.3 As part of site investigation, the designer shall draw up contingency plans for

further characterisation of critical parameters, which may include monitoring or ground investigation contemporaneous with construction.

4.5.3.4 Ground investigation will only be sanctioned where the quality of existing data isinsufficient to achieve the site investigation objectives; it is to be justified by theDesigner in Value Engineering terms. Ground investigation will normally beprocured and managed by the Corporation.

4.5.3.5 The objectives of the ground investigation shall be clearly stated in order thatappropriate techniques may be used. For instance, the additional expense of foam flushing and triple core barrels to obtain critical core recovery may be

justified in certain locations.

4.5.3.6 For economy, techniques should be adopted which satisfy multiple objectives.This is particularly relevant to proposals for field instrumentation, when costsmay be set against data acquisition requirements for more than one stage of design or construction.

4.5.3.7 Where an Observational Method (OM) of ground engineering is to be used,the ground investigation shall be planned to ensure, so far as is reasonablypracticable, that there is no likelihood of meeting unexpected conditions of asafety-critical nature. A sound appreciation of the range of geological and

hydrogeological conditions and potential engineering behaviour of the ground

materials must be obtained in order that the risk assessments required by theFactories and Industrial Undertakings (Safety Management) Regulation for allstages of construction may be adequately carried out. This may require theground investigation phase to extend into the construction phase.






4.5/3

4.5.4 EXTENT

4.5.4.1 The extent of the investigation will depend on the magnitude of the project, thecomplexity of the geological and geotechnical conditions, the relationship of the

proposed structure to those conditions, and the risk to existing adjacentstructures and features. The type, location, spacing and depth of exploratoryholes are site dependent but general guidance is included in Table 4.5.T1.

4.5.4.2 Where possible, a phased approach should be adopted for the ground

investigation.

4.5.5 CONTAMINATED LAND

4.5.5.1 The particular circumstances for the investigation of contaminated land shall be

recognised. The sampling pattern developed at planning stage shall relate toeither:

i) the particular contaminant sources identified during the feasibility study,i.e., judgemental sampling; or

ii) the areas within which sources were not identified but there are groundsto believe contamination is present - ie, regular sampling.

4.5.5.2 In the case of regular sampling a triangular grid shall be used the size of whichshall be related to the potential size of contamination source. A phasedapproach is recommended and a number of points shall be included to monitor background levels of contamination of both soil and groundwater in the first

phase. The vertical distribution of samples shall be assessed on the basis of site specific data.

4.5.5.3 The investigation of contaminated land will also require special techniques and

precautions. The details of sampling technique and safety requirements areincluded in the Materials and Workmanship Specification.

4.5.6 PUMPING TEST

4.5.6.1 Groundwater pumping tests shall be conducted to develop design parametersfor construction dewatering schemes and at locations where the groundpermeability is likely to affect the construction activities, e.g. where an oldseawall runs across a station.



Section 4: Civil Engineering


NWDSM-Section 4(4.5)-A5

4.5/4

Table 4.5.T1 Minimum Ground Investigation Guidelines

Features Minimum Number of Investigat ion Stat ions Addit ional Requirements

Stations and Ancillary Buildings 1 per grid spacing of 30m

Depot

a) Buildings

b) Track areas

1 per grid spacing of 30m

1 per grid spacing of 75m

Tunnels

a) Bored tunnels in rock 1 per 150m of alignment 1 every 10 boreholes should terminate

2.5 times the tunnel diameter below thinvert.

b) Bored tunnels in soil 1 per 30m of alignment

c) Cut and cover tunnels 1 per 50m of alignment

d) Shafts 1 per shaft

e) Portals 4 per portal 1 horizontal borehole of at least 50

length along the tunnel alignment

Viaduct Structures 1 per 50m of alignment

At-grade Railways 1 per 100m of alignment

Immersed Tube Tunnels 1 per 150m of alignment



Section 4: Civil Engineering


NWDSM-Section 4(4.5)-A5

4.5/5

Features Minimum Number of Investigat ion Stat ions Additional Requirements

Notes :

1. This table establishes minimum Acceptance Criteria for Detailed Design. A ground investigation proposed shall be subDesign respectively for acceptance.

2. Investigation station for the purpose of these Design Criteria means an existing or proposed exploratory drillhole, co

investigation feature as accepted.




4.6 Geotechnical Design


4.6/1

4.6 GEOTECHNICAL DESIGN

4.6.1 SCOPE

4.6.1.1 This subsection defines the required methods for geotechnical design. It issubdivided as follows.

i) 4.6.2 Reclamations

ii) 4.6.3 Waste Landfillsiii) 4.6.4 Slopes and Embankmentsiv) 4.6.5 Surface Excavationv) 4.6.6 Underground Excavationvi) 4.6.7 Retaining Structures

vii) 4.6.8 Foundations

viii) 4.6.9 Trackform Substructureix) 4.6.10 Ground Bolts & Anchorsx) 4.6.11 Blast Design and Vibrations

4.6.1.2 The loads and forces derived shall in all circumstances be working loads or forces which define a serviceability limit. Movements determined as a result of the working loads or forces shall also relate to a serviceability condition. Thefactors of safety then applied shall relate to the ULS – e.g., slope stability,

bearing capacity.

4.6.1.3 Where partial factors of safety are applied to design parameters, such as in thedesign of retaining walls in accordance with Geoguide 1 and in design of geosynthetics, particularly in ground reinforcement applications in accordance

with BS 8006, the overall factor of safety will be corresponding reduced.

4.6.2 RECLAMATIONS

Scope

4.6.2.1 This subsection addresses the design requirements of reclamations. Thisapplies to:

i) the design of new or primary areas of reclamation;

ii) the design of works to be sited on or in a position to be influenced byexisting areas of reclamation; and

iii) the design of seawalls for containment of reclaimed areas.

Reclamation Design

4.6.2.2 For construction on reclaimed areas, the long term movement performance andthe compaction characteristics of the fill shall be determined. This will involve areview of the construction records for the reclamation and an appropriate levelof site investigation. The predicted long term movements shall satisfy the






4.6/2

design requirements of the works. If necessary, improvement works may needto be carried out to the reclamation to limit long term movements.

4.6.2.3 The allowable settlement and angular distortion occurred after the completion of

any structures not supported on deep foundations shall not exceed 50mm and1:1000, respectively. Should this be impractical a maintenance programme hasto be worked out (e.g. the frequency of relaying the sub-ballast). For tracks, asuitable trackform should be selected to minimize the maintenance cost. All theabove should be compared with the cost of providing a deep foundation.

4.6.2.4 The final reclamation level shall be established based on the HKPWDM and therequirements of the NWDSM, and shall be subject to the approval of theCorporation.

Seawalls

4.6.2.5 Stability analysis of seawalls shall be in accordance with Subsection 4.6.4. For temporary conditions during construction, a minimum factor of safety of 1.2 for

stability shall be maintained at all times. The design of permanent seawalls, thefailure of which would directly impact on railway installations, shall be inaccordance with the Geotechnical Manual for Slopes and a minimum factor of safety of 1.4 shall be maintained. Where the failure of a seawall would notdirectly impact the Railway then it shall be designed for stability in accordance

with the HKPWDM.

Dynamic Response - Seawall

4.6.2.6 Seawalls shall be designed for the effect of earthquake loading in accordancewith Subsection 4.4. The overall stability of the seawall structure subject toearthquake loading shall be checked in accordance with GEO Report No. 15.Guidelines for assessing the lateral pressure on seawalls due to dynamicloading are given in GEO Report No. 45. Liquefaction of seawall base shall

also be evaluated in accordance with Cl.4.6.2.7.

Dynamic Response - Reclamation

4.6.2.7 The liquefaction potential of the reclamation shall be assessed and designed to

avoid liquefaction due to a peak ground acceleration of 0.15 g. Single sized

materials are generally more susceptible to liquefaction than well gradedmaterials. Fine clean sands tend to liquefy more easily than coarse sands,gravelly soils, silts or clay. Refer to the GCO Technical Note TN5/91.

4.6.3 WASTE LANDFILLS

Scope

4.6.3.1 This subsection addresses the design of Works on or through proposed or existing waste landfills. Waste landfill means an area of made ground formedfrom a mix of domestic, industrial and construction waste.






4.6/4

Landfill Cover Systems within the Works

4.6.3.7 Where existing waste landfill is required to be covered as part of the Works thecover system shall be designed to achieve the factors of safety against slope

instability stipulated in GEO Paper No. 260 and to satisfy EPD requirements.

4.6.3.8 Where a mineral (clay layer) cover to the landfill is used it shall have an in placepermeability of less than 1x10-9 m/sec and a minimum thickness of 1 m.

Synthetic cover barrier systems such as bentonite mats, HDPE, MDPE, LDPEor VLDPE (High to Very Low Density Polyethylene) membranes may also beused as part of the cover, where appropriate.

Surface Water Drainage

4.6.3.9 Surface drainage system shall not be allowed to discharge water into the landfill

waste. Any existing stream or watercourse which discharges into the wasteshall be intercepted and diverted into the new surface water drainage system.

Landscaping

4.6.3.10 Landscaping of waste landfill (including cover) shall be designed to ensure thefollowing.

i) Plants do not reduce the effectiveness of the landfill cover system andcause increased water infiltration into the waste landfill.

ii) The stability or thickness of the landfill cover system is not reducedbelow required levels.

Landfill Gas

4.6.3.11 Detailed gas migration monitoring shall be carried out at the proposed locations

of the structures over a sufficiently long period of time to define seasonalvariations. This requires the installation and monitoring of gas migrationmonitoring boreholes. Monitoring shall include but not be limited tomeasurements of the concentrations of the landfill gas. Where appropriate,modelling shall be carried out to estimate the migration pattern of gas using

validated computer programs approved by the Corporation.

Landfill Gas Control Measures

4.6.3.12 During the design process an assessment shall be made of the compositionand quantities of landfill gas and the long term effects on the Railway. Basedon this assessment and the EPD performance requirements either an active(pumped) venting system or a passive (unpumped) venting system may berequired to control waste landfill gases. Particular care shall be exercised in the

design of gas venting for any underground openings in waste landfills.Wherever possible such should be avoided.

4.6.3.13 The following measures or combination of measures shall be incorporated intothe design of the gas control system.






4.6/5

i) Gas venting trenches and pipes.ii) Gas cut-off walls.iii) Gas cut-off membranes.iv) Flaring of waste landfill gas.

Leachate Migration

4.6.3.14 When proposed structures are located in the vicinity of a waste landfill all of thefollowing investigations are required to evaluate the extent of leachate migration.

i) Monitoring of groundwater elevations and composition at the proposedstructure, over a sufficiently long period to define seasonal and annualvariations and including wet seasons.

ii) Groundwater flow modelling using validated computer softwareapproved by the Corporation.

iii) Contaminant plume migration modelling using validated computer software approved by the Corporation.

Leachate Control Measures

4.6.3.15 CIRIA Special Publication 124 provides a review of various methods of leachatecontrol and waste landfill containment systems. Where such control andcontainment is required these methods shall be reviewed and the most

appropriate systems proposed.

4.6.3.16 For construction near unlined waste landfills a containment wall may beincorporated in the design. Slurry trench cut-off walls may be used in soil, while

pressure injected grout curtains may be used in rock.

4.6.4 SLOPES AND EMBANKMENTS

Scope

4.6.4.1 This subsection considers embankments, or formed slopes, having a maximumsideslope gradient of 1 vertical on 0.35 horizontal, equivalent to an angle of 70°

measured from the horizontal. For the design of structures having sideslopegradients in the range of 70° to 90°, reference shall be made to subsection

4.6.7.

Groundwater Conditions and Drainage

4.6.4.2 Perched water table conditions may be assessed using the wetting bandapproach. The maximum height of the perched water table should not normallyexceed 3 m.

Bearing Capacity

4.6.4.3 A factor of safety of at least 3 shall be used to determine of the allowablebearing capacity of soil founding materials. Particular care shall be taken to

allow for weaker soil layers at depth in which failure could occur.






4.6/6

Slope Stability

Slopes and embankments should design to the minimum factors of safety as

defined in the Geotechnical Manual for slopes. Excess pore water pressuresshall be estimated at intermediate fill heights for input into stability analyses.The minimum factor of safety for slope stability shall be 1.2 during anytemporary construction stage. The excess pore pressures and overall stabilityshall be assessed at each stage of filling, such information being in the form of

control charts to be used during construction in conjunction with piezometer monitoring data. Only those soil slope stability analysis computer programswhich have been validated and subsequently approved by the Corporation or Buildings Department may be used. Other slope stability analysis computer

programs shall not be used unless approved either by the Corporation or by theBuildings Department.

Movements

4.6.4.4 Movement plots for comparison with field behaviour shall be developed andpresented:

i) along longitudinal sections of embankment; andii) at selected, critical cross-sections of the embankment

The above movements shall be determined for the anticipated constructionstages where applicable and at time intervals of; immediately, 3, 5, 10, 25, 50,and 120 years after construction for permanent structures with a Design Life of

120 years.

4.6.5 SURFACE EXCAVATION

Scope

4.6.5.1 This subsection addresses the design of the following main surface excavationstypes.

i) unsupported excavations where stability is achieved by providing stable

slopes; andii) supported excavations where the steep or (often vertical) sides are

supported by structure.

Unsupported Excavations Buried Services in Slopes

4.6.5.2 Buried services (particularly water carrying services) shall not be permitted inslopes unless there is no practical alternative. For guidance on providing

services in slopes, reference shall be made to PNAP APP-76 and Code of Practice on Inspection and Maintenance of Water Carrying Services AffectingSlopes.






4.6/7

Design - Soil Slopes

4.6.5.3 Modifications to an existing slope occasioned by new works will mean that themodified slope shall be treated as part of the new works and as a result subject

to the minimum factors of safety defined in the Geotechnical Manual for Slopes.

4.6.5.4 Only those soil slope stability analysis computer programs which have beenvalidated and subsequently approved by the Corporation or BuildingsDepartment may be used. Other slope stability analysis computer programsshall not be used unless approved either by the Corporation or by the BuildingsDepartment.

Groundwater - Soil Slopes

4.6.5.5 For design at feasibility stage and in the absence of site specific data, the

minimum wetting band thickness shall be taken as 1.5 m located anywhere inthe soil profile which results in the most critical conditions for slope stability.

Surface Protection and Support - Soil Slopes

4.6.5.6 Vegetation shall be considered as the principal method of covering for newlyformed or regraded soil slopes. Where necessary consideration shall be givento the use of biodegradable or geosynthetic matting or other forms of protection(e.g., geoweb) to ensure that erosion is minimised.

Groundwater - Rock Slopes

4.6.5.7 If rock slopes or portals are to be retained for the Design Life of the Railway,then a groundwater drainage system shall be designed to ensure that the

various groundwater levels assumed in the design of the rock slopes andportals will be maintained throughout the Design Life of the Railway.

4.6.5.8 The effect of blasting for rock excavation on the permeability of the rock massand the impact on water inflows into the excavation shall be included in the

tunnel seepage analysis.

Stabilisation - Rock Slopes

4.6.5.9 On the basis of the rock slope stability analyses, the design and associatedstabilisation measures shall be proposed to ensure that during and after construction no rock blocks are released from the rock slope. The evaluation of rockfall and required control shall be carried out in accordance with theGeotechnical Manual for Slopes.

4.6.5.10 The design of dowels, rock bolts and anchors shall be in accordance withsubsection 4.6.10.

Tunnel Portals - Soil and Rock

4.6.5.11 Design of tunnel portal slopes will have to be allowed for blasting effect shouldblasting be adopted as the excavation means.






4.6/8

Supported Excavations Design of Excavation Support Systems

4.6.5.12 Where excavations are adjacent to EBS sensitive to movement, computer modelling of the excavations and support systems shall be carried out using

validated either finite difference or finite element based computer programsapproved by the Corporation. The results obtained by numerical modellingshall always be verified with other established empirical design procedures.

Design Parameters

4.6.5.13 The design parameters, in particular stiffness, assigned to regions of thecomputer model shall be selected with due regard made to the magnitude anddirection of stresses and strains likely to be experienced by that region of the

model.

4.6.5.14 When carrying out computer modelling, soil parameters back-calculated fromsimilar existing structures may be used. However, the back-calculation of parameters shall be carried out using the same computer program that will be

used in the analysis for the new works. The use of back-calculated soilparameters shall be subject to the approval of the Corporation.

Design Loads

4.6.5.15 Loads shall be determined in accordance with Subsection 4.4. In addition, anominal uniformly distributed construction loading of 10 kPa shall be applied atthe ground surface immediately behind the excavation support for a distance, atleast equivalent to the depth of the excavation or all the area within the failure

zone, whichever is greater.

Groundwater Levels

4.6.5.16 The design groundwater levels shall be in accordance with Subsection 4.4. The

impact of the proposed excavation works on groundwater levels shall be limitedin accordance with Subsection 4.3.

Vertical and Lateral Movements

4.6.5.17 In areas where movements caused by the proposed excavation will have no

significant impact on adjoining areas (e.g., green field sites) then suchmovements may be predicted using empirical or semi-empirical methods.Where the proposed excavations are in movement sensitive areas (e.g.,

adjacent to sensitive EBS) then detailed methods such as finite elementanalysis shall be used to predict the resulting movements.






4.6/9

4.6.6 UNDERGROUND EXCAVATIONS

Scope

4.6.6.1 This subsection addresses the design of underground excavations in soil androck. Refer to subsection 4.3 for details on design requirements for underground openings.

Definitions

4.6.6.2 Refer to subsection 4.3.3 for definitions of Temporary or Initial Support, PrimaryLining, and Secondary Lining.

Rock Material and Rock Mass Properties

4.6.6.3 The rock conditions at the Site shall be categorized by the NorwegianGeotechnical Institute (NGI) Q-system in accordance with Grimstad & Barton,

1993 where Q is the rock tunnelling quality index.

Loadings

4.6.6.4 As mentioned in subsection 4.3.3, generally all permanent underground

openings shall be designed for the full water pressure head around the openingperiphery. The minimum water pressure head to be considered shall beequivalent to a water level 10 m above the crown of the underground opening.Where a pressure relieved opening form is accepted by the Corporation the

lining shall be designed for the minimum water pressure head as defined abovedown to axis level, reducing to zero water pressure head at the invert.

Temporary Support Design

4.6.6.5 The preliminary design of rock temporary support may be based on empiricalmethods using the Q rock mass classification system. Temporary support mayalso be designed based on the predicted extent of the failure zone surroundingthe excavation as determined from analytical methods. However, sufficientallowance shall be made for monitoring of movement and installation of

additional support if dictated by conditions and/or monitoring records.

4.6.6.6 Where stability of rock underground excavation is likely to be controlled by thegeological structure in the rock mass discrete element methods of analysis shallbe used. Proposed computer programs shall be submitted for approval to the

Corporation.

Permanent Support Design – General

4.6.6.7 The permanent support and lining to the underground excavation may comprisethe primary lining, the secondary lining or a combination of the two. Thepermanent support and lining may also comprise permanent dowels, nails of bolts, fibre reinforced or plain shotcrete, cast-in-situ concrete and steelsegments.






4.6/10

4.6.6.8 Where open face methods of excavation are adopted, it shall be assumed thatthe temporary support does not contribute to be capacity of the permanentsupport or lining in any way.

Permanent Support Design – Soil

4.6.6.9 The permanent support/lining constructed in soil in conjunction with shieldexcavations may comprise a primary lining followed by secondary lining. Theprimary lining shall be designed for the effects of the shield jacking loads,

calculated in accordance with Szechy, 1966 and as summarised in Whittaker &Frith, 1990. A minimum factor of safety of 1.5 shall be applied to the shieldshove jack load when determining the structural adequacy of the primary lining.

Permanent Support – Rock

4.6.6.10 Permanent linings for underground excavations in rock shall be designed towithstand rock loading defined by:

i) an equivalent permanent support pressure applied uniformly to the fullspan of the opening and taken as:

Proof = 2 Jn0.5 Q-0.33 / 3Jr (Kg/cm2)(after Grimstad & Barton, 1993)

Where, Jn = Joint set number (Geoguide 4)

Q = Tunnelling Quality Index (Geoguide 4)Jr = Joint Roughness Number (Geoguide 4)

and;

ii) the weight of potentially unstable wedges applied as a distributed loadover the exposed area of the wedge as determined from structurallycontrolled instability analysed by hand or by validated and approvedcomputer games.

4.6.6.11 Where it is impractical to design the rock permanent lining to withstand the fullloading then subject to the approval of the Corporation permanent rock dowelsof bolts shall be designed in accordance with the relevant provisions of

subsection 4.6.10.

4.6.7 RETAINING STRUCTURES

Scope

4.6.7.1 This subsection addresses the design of retaining structures and indicatesareas of potential application and identifies parameters that need to bedetermined when designing such structures.






4.6/11

Design Parameters

4.6.7.2 In accordance with Geoguide 1, walls with a retaining height of up to 3 m shallbe designed using geotechnical parameters selected on the basis of previous

test results on similar materials. For walls with retaining heights greater thanabout 3 m, geotechnical parameters shall be determined from site investigationand laboratory tests or appropriate field tests.

Reinforced Fill Structures

4.6.7.3 The corrosion of galvanised metal reinforcing strips shall be monitored by theinclusion of 1 m long test strips within the structure and which are capable of being extracted through the facing panels at periods of 5, 25, 50, 100 and 120

years after the completion of construction. These test strips shall be installedwithin panels at one-third and two-thirds of the wall height, with a minimum of

three to be extracted at each time period from each level. The effect of straycurrents upon these types of structures shall be carefully assessed andappropriate design measures incorporated into the design.

Dry Stone (Masonry) Walls

4.6.7.4 Masonry walls shall not be used as retaining structures, except when used for

landscaping to a maximum height of 1.0 m. Such walls shall be designed asgravity walls.

Mass Concrete Gravity Retaining Walls

4.6.7.5 Mass concrete retaining walls may be used for retained heights of up to 3 m. Above this height the economic viability of such structures shall bedemonstrated to the satisfaction of the Corporation.

4.6.8 FOUNDATIONS

Scope

4.6.8.1 This subsection addresses the design of foundations. All foundations exhibitmovement. Such movements shall satisfy the project and supported structure

requirements and structure design criteria. Foundations may be either shallowor deep.

4.6.8.2 The use of hand dug caissons is discouraged for reasons of health and safety.They may only be used where it can be demonstrated that their use is the onlypractical construction method or there is no other safe alternative.

Foundation Loading Conditions

4.6.8.3 For the assessment of foundations bearing capacity the full dead load plus100% of the live load as defined in Subsections 4.2 and 4.3 and in the followingparagraphs shall be included. For the estimation of total (primary and

secondary) movement the full dead load plus 50% of the live load shall be






4.6/12

included. Wind loads shall be taken into account in the design in accordancewith in Subsections 4.2 and 4.3 and Hong Kong Code of Practice for Foundation.

4.6.8.4 Foundations shall be designed for earthquake loading in accordance withSubsection 4.4.

4.6.8.5 Where eccentric loading conditions occur the maximum applied pressure at theunderside of the foundation shall not exceed the allowable bearing pressure of

the supporting ground.

Factor of Safety - Compression

4.6.8.6 For compressive loading the allowable bearing pressure of foundations shall betaken as the ultimate bearing capacity divided by a factor of safety of 3.

Factor of Safety - Tension

4.6.8.7 The design of foundations subject to tension or uplift shall be in accordancewith GEO Publication 1/96. Side friction to resist uplift shall not be assumed for shallow foundations without specific approval of the Corporation. The ultimateuplift capacity of piles shall be checked for potential failure mechanismsincluding:

i) failure in friction along pile shaft; andii) weight of cone of rock with the semi-apex angle equal to 30°, and 10°

for the soil above.

Foundations - Negative Skin Friction

4.6.8.8 For the design of foundations which are not subject to Sections 26 to 31 of theBuilding (Construction) Regulations, 1990, transient loads such as live loads

and wind loads when considered in combination with negative skin frictionreduced partial load factors may be adopted subject to the approval of theCorporation.

4.6.8.9 Proposal for bitumen or slip coats applied on pile surface to reduce the effects

of negative skin friction shall be submitted for acceptance.

4.6.9 TRACKFORM SUBSTRUCTURE

Scope

4.6.9.1 This subsection addresses the specific geotechnical considerations for thedesign of support for ballasted or non-ballasted trackform on subgrade. Whilst

both ballasted and non-ballasted trackforms may be used on elevatedstructures, bridges and in tunnels, this section of the Manual deals only withtheir use at grade where the trackform is to be constructed on ground whether natural or man made.






4.6/13

4.6.9.2 The trackform substructure shall be assumed to comprise the ballast,subballast, subgrade and the adequacy, movement and drainage thereof. Thetrackform substructure shall be designed to limit the subgrade pressure causedby the train wheel loads to the allowable subgrade pressure. Alternatively the

subgrade may be improved to increase the allowable subgrade pressure.

4.6.9.3 Ballasted track shall normally be specified for all of the Corporation at gradetrackform. Non-ballasted trackform shall only be used at grade where shortsections (less than 300 m) exist between longer adjacent sections of

non-ballasted trackform.

Trackform Movement

4.6.9.4 The allowable total and differential movement of the at grade trackform shall bespecified in the Functional Requirements Manual.

4.6.9.5 The following shall be checked in the design of each section of substructure:

i) Bearing Capacity

The bearing capacity of the subgrade shall be assessed in accordancewith Geoguide 1 (refer to subsection 4.6.8) and checked for the possiblemodes of bearing capacity failure being failure of individual sleepers and

of the whole track, assuming that the track system acts as an infinitelylong footing.

ii) Slope Stability

Where the track subgrade is bounded by slopes the stability of theseshall be assessed in accordance with subsections 4.6.4, 4.6.5 and 4.6.6,as appropriate for embankment or cut slopes.

iii) Movement

Movement of the substructure and subgrade shall be determined inaccordance with the requirements of subsection 4.6.4. Particular careshall be taken with the design to accommodate differential movements

across different types of subgrade.

Ballast

4.6.9.6 The ballast material shall be designed to;

i) resist vertical, lateral, and longitudinal forces;ii) absorb energy;iii) provide immediate drainage; andiv) reduce stresses from the sleeper bearing area to acceptable levels for

the underlying materials.

4.6.9.7 The ballast shall have a minimum thickness of 300 mm below the underside of sleepers and shall conform to the requirements defined in the Materials and






4.6/14

Workmanship Specification.

Subballast

4.6.9.8 The subballast shall be designed to fulfil the functions of separation being to;

i) prevent upward migration of fines from the subgrade;ii) provide support to the ballast;iii) allow subballast and subgrade drainage;

iv) reduce stresses on the subgrade.

4.6.9.9 The upper surface of the subballast shall be laid to a minimum crossfall of 1 in40.

4.6.9.10 The subballast shall have a minimum thickness of 200 mm between the base of

the ballast and the top of the subgrade and shall conform to the requirementsdefined in the Materials and Workmanship Specification.

4.6.9.11 In addition, in order to perform its function as a filter and separator thesubballast material shall comply with the following.

D15 (subballast) < 5D85 (subgrade)

D50 (subballast) < 25D50 (subgrade)

4.6.10 GROUND BOLTS AND ANCHORS

Scope

4.6.10.1 This subsection addresses the design of temporary and permanent bolts and/or anchors used as reinforcement for stabilisation and support of groundexcavations.

Terminology

4.6.10.2 The term ‘bolt' shall refer to a single, tensioned or untensioned, bar with a yieldstrength of less than 460 MPa, with or without a face plate and anchored in rock.

4.6.10.3 The term ‘anchor' shall refer to multiple, tensioned or untensioned cables or strands with an yield strength greater than 460 MPa, with or without a faceplateand anchored or grouted in soil or rock

4.6.10.4 The term ‘nominal failure load' shall refer to the ultimate failure capacity of thecompleted bolt installation.

Design - Temporary Bolts and Anchors

4.6.10.5 The design of temporary bolts for underground openings shall be in accordancewith Geoguide 4. Simple bolting systems, such as untensioned bolts or dowelswith full column bonding provided by cement or resin grout, shall be adopted






4.6/16

4.6.10.15 Fully bonded permanent bolts shall be formed from grade 460 steelgalvanised with a minimum uniform coating of 0.2mm and provided withdouble corrosion protection system in accordance with BS 8081 (min 5mmcover 60 bar). A 2mm sacrificial annulus shall be allowed for when

determining working loads.

4.6.11 BLAST DESIGN AND VIBRATIONS

Scope

4.6.11.1 This subsection addresses the requirements for blast design, the restrictions onvibrations and air pressures generated, the assessment of effects of blasting

and the control of blasting by regulatory bodies.

4.6.11.2 For a preliminary assessment of the vibrations likely to result from blasting, thefollowing formula, derived from the United States Bureau of Mines shall be used.

ppv = K(R/WB) A,

where, ppv = peak particle velocity (mm/s)

R = distance between blast and measuring point (m)W = maximum charge weight per delay interval (kg)K = rock transmission constantB = charge exponent normally taken as 0.5 A = attenuation exponent.

4.6.11.3 For predicting blast vibrations the constants adopted by the Commissioner of Mines are recommended:

K = 644 and A = -1.22 at 84% confidence.

K = 1032 and A = -1.22 at 95% confidence.

4.6.11.4 In assessing blasting induced vibration restrictions the relationships between

frequency (f), maximum amplitude or (peak particle displacements) (ppd), peakparticle velocity (ppv) and peak particle acceleration (ppa) shall be taken as:-

ppv = 2πf ppd 10-³ mm/s (ppd in mm, f in Hz)

ppa = 2πf ppv 10-

³ mm/s²

4.6.11.5 The design of blasts in confined areas shall demonstrate that air overpressuresare within safe and reasonable limits. The following equation shall be used topredict air overpressure from small diameter, unstemmed blastholes:

dBL = 180 - 24 log(R/W0.333)

where dBL is the overpressure decibel (linear weighting), and R and W are

defined above. A maximum limit of 130 dBL shall be adopted for blasting tominimise human discomfort. Where expected air overpressures exceed 78 dBL,methods to maintain this level in public areas shall be submitted for theapproval of the Corporation.






4.6/17

Blasting Restrictions

4.6.11.6 The effects of any proposed blasting on existing Corporation installations shall

initially be assessed by reference to PNAP APP-24. Where the restrictionsimposed by PNAP APP-24 on blast design are considered to be too severe or potentially unreasonable and in order for the progress of the Works to complywith the construction programme, then higher vibration limits may be proposed,subject to the approval of the Corporation.

4.6.11.7 Proposals for ppv limits higher than the PNAP APP-24 limits shall be discussedin the Blast Risk Report with justification initially based on existing data, whereavailable, and subsequently upon fully instrumented and monitored trial blasts.

4.6.11.8 The Commissioner of Mines normally imposes vibration restrictions by limiting

peak particle velocity (ppv) generally to 25 mm/s or less for EBS – refer to thesummary in the M&W Specification. The ppv restriction will be lower for services and utilities, where computer installations are present and for medical

or educational establishments.

4.6.11.9 The limits for blasting vibration imposed by the principal utility companies inHong Kong on their installations are summarised in the M&W Specification.




4.7 Instrumentation and Monitoring


4.7/1

4.7 INSTRUMENTATION AND MONITORING

4.7.1 SCOPE

4.7.1.1 This subsection addresses the design and definition of instrumentation andmonitoring for the works. The monitoring instruments shall be installed for thepurpose of monitoring ground and structure movements, groundwater andstructural behaviour prior to construction, during construction and following

completion of construction in certain cases.

4.7.2 INSTRUMENTATION & MONITORING DESIGN

4.7.2.1 The purpose of monitoring at any stage of the Works is generally for the

following reasons:

i) to define initial site conditions including the identification of water levels

and providing a means of assessing in situ stress conditions;

ii) to determine the trends in structure and ground behaviour, to verifydesign predictions and to determine by backanalysis the in situproperties of the ground such that they can be used in subsequent

design;

iii) to monitor in-service performance - e.g., variations of stress in piles or stone columns, structures and ground;

iv) during construction to identify undesirable magnitudes or trends inmovement, pore water pressures and the like for which remedial actionmay need to be implemented;

v) to exercise construction control - e.g., piezometers for the rate of construction of embankments, inclinometers to identify the time for installation of propping or excavation stages; and

vi) during construction to identify areas in which the quality of work is

inferior and for which further works (e.g., support) may be required.

4.7.2.2 The monitoring of other factors, (e.g., corrosion or stray current; or instrumentation used to control specific construction procedures, such asvibrated concrete columns, excavated piles/barrettes, jet grouting and the like)

are specifically excluded from this section.

4.7.2.3 The instrumentation shall be kept as simple and robust as practicable so as toensure ready derivation of the information provided by the instrument and thelongevity of the instrument. The method of monitoring the instrument shall be

similarly simplified so that the information provided by that instrument is clear,unequivocal and within the appropriate accuracy, precision and repeatability of that instrument.






4.7/3

piezometric surface(s) can be defined across the area of the proposeddevelopment together with their seasonal variations.

4.7.2.9 All instrument monitoring shall be carried out over a period not less than 3

months prior to construction or at interval agreed with the Corporation.

4.7.2.10 During the course of appraising and re-appraising construction options thescope of installed instrumentation shall be regularly re-evaluated. Wherenecessary, consideration shall be given to extending the level of data available

or filling gaps in knowledge in order to optimise particular designs.

4.7.2.11 Instrumentation shall be selected to suit the circumstances of the item of theWorks to be monitored. The proposed instruments are required to submit to theCorporation for approval.

4.7.2.12 The required accuracy, precision and repeatability for each and everyinstrument shall be defined and shall relate to the specified Alert and Actionlevels.

4.7.2.13 Instrumentation and Monitoring drawings shall be prepared taking duecognizance of the foregoing which clearly indicate the instrumentation andmonitoring requirements for the contract.

4.7.3 MONITORING

Alert and Action Levels

4.7.3.1 The Alert and Action levels for each and every instrument shall be as defined inaccordance with Subsection 4.2.

Baseline Monitoring

4.7.3.2 The latest date for installing specific instruments shall be specified in order toobtain adequate baseline readings - refer to Subsection 4.7.2.

Method and Frequency of Monitoring

4.7.3.3 The specified method and frequency of monitoring shall be sufficient to provideadequate advance warning of approach to the Alert and Action levels. However,the method shall not be so complicated nor the frequencies so great that these

impose unnecessary logistic or economic burdens.

Monitoring Locations

4.7.3.4 The selection of monitoring locations shall reflect the predicted behaviour and

shall be compatible with the method of analysis that will later be used wheninterpreting the data.

4.7.3.5 More than one instrument type should not be installed at the same locationunless it can be clearly demonstrated that either the installation or monitoring






4.7/4

methods of one instrument will not influence the integrity or action of the other.

4.7.3.6 The location level of each and every instrument installed shall be defined. Inall cases, records from each and every instrument shall be related to absolute

levels or locations - e.g., surveyed co-ordinates. Instruments shall not beinstalled where this cannot be complied with.




4.8 Structural Design


4.8/1

4.8 STRUCTURAL DESIGN

4.8.1 SCOPE

4.8.1.1 This subsection describes the analysis, design and detailing requirements for structural materials in civil engineering or building works.

4.8.2 DYNAMIC ANALYSIS

4.8.2.1 Where structural elements dynamic effects have been defined in Subsection4.4 (or are considered) as not being adequately allowed for by the dynamic load

factors defined in HKSDM or elsewhere as appropriate, detailed analyses anddesign shall be carried out.

4.8.3 EARTHQUAKE ANALYSIS

Above Ground Buildings

4.8.3.1 Above ground buildings shall be considered on an individual basis when

designing for earthquakes. A design philosophy statement shall be submitted inthe Approval in Principle Document (AIP) for the approval of the Corporation.The design and analysis philosophy shall follow the proposals laid down in theNew York City Seismic Code.

4.8.3.2 Spectral and soil parameters shall be modified to suit Hong Kong conditions inaccordance with the proposals in the paper “Seismic Design of Buildings inHong Kong” by Scott, Pappin and Kwok presented at the ‘Earthquake ResistingStructures’ seminar on 3rd May 1996. However, for buildings of less than 30 min height, the minimum horizontal earthquake force used in design shall be notless than 5% of the total attributable vertical loads as described in Subsection4.4.13 unless the fundamental period is calculated using the structural

properties and deformational characteristics, as permitted by the New YorkCode. Such calculation shall be carried out by computer analysis.

4.8.3.3 The design philosophy statement shall include, but not be limited to, the

following:-

i) a description of the proposed procedure for the analysis and design of the structure;

ii) proposed Zone Factor Z, Spectral Factor C, Soil Factor S, Response

Modification Factor Rw, partial load factors and load combinations;

iii) the calculated natural period of the structure based on a preliminary

assessment by computer frame analysis;

iv) description and comment on the soil conditions and applicability of the

Spectral Factor C noted in the paper above for the particular structure,






4.8/2

with recommended value for use;

v) a comparison of seismic base shears with those produced by wind

loading;

vi) discussion of the period related lumped mass on the top of thestructure;

vii) a method for the treatment of any 'soft storeys', discussion of any

structure eccentricities and torsional or mass irregularities;

viii) comment on seismic sensitivity of the structure with respect to stiffness;

ix) consideration of pounding effects across joints and the joint dimensionrequired to minimise/nullify impact loading, particularly at floor slabs andwalls/columns which are not on the same line/level.

4.8.3.4 The System Factor Rw shall be as follows:

i) Ordinary Moment Frame Structures Rw = 4

ii) Shear Wall Structures Rw = 6

iii) Transfer Structures Rw = 3

4.8.3.5 For Ordinary Moment Frame structures alternative Rw factors may be proposedwith the necessary justification, a greater Response Modification Reduction

Factor may be proposed provided reinforcement detailing is adopted, to ensureadequate frame ductility, in accordance with the UBC.

Bridges

4.8.3.6 Bridge design and analysis shall comply with the American Association of StateHighway Transport Officials (AASHTO) - Standard Specification for HighwayBridges, Seismic Design. Spectral and soil parameters shall be modified asdescribed in Cl.4.8.3.2. for Hong Kong conditions. However, in no case shall

the loads and requirements used in design be less than those that would bederived from Subsection 2.6 of HKSDM.

4.8.3.7 The Seismic Performance Category (SPC) shall be taken as 'B' and theacceleration coefficient 'A' as 0.15.

4.8.3.8 The additional earthquake forces shall be applied in conjunction with any pre-existing soil loads (active or at-rest as appropriate) or water loads. Whenderiving the dynamic component of earthquake load, the bulk unit weight shallbe used for soil above and below water level since the pore water will move with

the soil particles and experience the same acceleration.

Free Standing Retaining Walls

4.8.3.9 For free standing retaining walls the method of analyses as described for Abutments in the AASHTO – Standard Specification for Highway Bridges,

Seismic Design shall be adopted for determining additional earthquake lateral






4.8/3

soil pressures. An allowance shall be made for wall restraint , the restraintmodification factor adopted shall be determined in accordance with thefollowing:

i) For retaining walls which may displace horizontally without significantrestraint (e.g. ground bearing) seismic coefficients of Kh = 8% and Kv =4% shall be used.

ii) For retaining walls which are partially restrained (e.g. vertically piled)

seismic coefficients of Kh = 24% and Kv = 12% shall be used.

iii) Retaining walls which are unable to move or rotate at all, or are subjectto earthquake loads from an attached structure, shall be subject toindividual consideration. In this extreme case dynamic ground pressure

loads shall be justified on a case by case basis, after consultation with

the Corporation.

4.8.3.10 Cl.4.8.3.12 requirements for forces and the use of bulk unit weight whenderiving loads above and below water shall also apply to retaining walls.

Underground Structures

4.8.3.11 Earthquake loading due to ground shear deformation from the bedrock motion

shall be allowed for on underground structures. A statement describing thedesign philosophy shall be submitted in the AIP and subject to the approval of the Corporation. The design and analysis philosophy shall follow the proposalslaid down in the paper published by the Earthquake Engineering Committee of Japan Society of Civil Engineers - Earthquake Resistant Design Features of

Submerged Tunnels In Japan. The statement shall demonstrate how vertical,transverse and longitudinal earthquake load effects will be allowed for.

4.8.3.12 The design philosophy statement shall include, but not be limited to, thefollowing:

i) a description of the proposed procedure for the analysis and design of the structure;

ii) consideration of the forces induced in structural elements by the

structure tending to follow the shear deformation of the surroundingground mass;

iii) consideration of the forces induced in structural elements by the

structure tending to resist the shear deformation of the surroundingground mass;

iv) consideration of the forces induced at any interfaces betweenstructures of different stiffness and seismic response such as station to

tunnel connections and the like;

v) consideration of the forces induced in structures founded in ground with






4.8/4

significant variations in stiffness;

vi) discussion of soil liquefaction potential and resultant effects;

vii) discussion of ground movements - vertical and horizontal; and

viii) any other effects relevant to the particular structure, adjacentCorporation structures or other infrastructure under consideration.

4.8.3.13 The additional earthquake forces shall be applied in conjunction with any pre-existing soil loads (active or at-rest as appropriate) or water loads. Whenderiving the dynamic component of earthquake load, the bulk unit weight shallbe used for soil above and below water level since the pore water will movewith the soil particles and experience the same acceleration.

4.8.4 FATIGUE ANALYSIS

General

4.8.4.1 Fatigue design shall comply with the requirements of “Hong Kong Code of Practice for the Structural Use of Steel” and HKSDM for all structures whichsupport railway, road or other significant cyclic loading.

4.8.4.2 For both concrete and steelwork structures stress ranges induced by railwayvehicles shall be combined with any other cyclic effects due to vehicles or other loading to which the structure may be subject when considering cumulative

damage.

Concrete

4.8.4.3 For reinforced concrete BS5400, Part 4, Cl. 4.7 shall be modified in accordance

with UK Highways Agency Standard BE21/14/014 for rail, road and other cyclicloads.

4.8.4.4 For unwelded reinforcing steel in concrete fatigue consideration may be basedon the simple maximum stress range check given in the BE21/14/014. For

structures subject to railway vehicle effects the maximum stress range shall be

derived based on the fatigue axle loads and axle spacings given in Subsection4.4. positioned to give the most onerous stress level for the element under consideration. Where a more sophisticated analysis in accordance withHKSDM Chapter 10 is considered appropriate the design stress history for

railway vehicle effects shall be derived in accordance with Cl. 4.8.4.7 using theBE21/14/014 values for the σr -N relationship parameters m and k2.

4.8.4.5 For welded reinforcing steel in concrete fatigue design shall comply with therequirements for steelwork elements given in Cl. 4.8.4.6 and Cl.4.8.4.7 using

the appropriate detail classifications given in HKSDM Chapter 10.






4.8/5

Steelwork

4.8.4.6 Steelwork and concrete incorporating welded reinforcing steel which supportsrailway, road or other significant cyclic loading shall be designed for fatigue in

accordance with the provisions of HKSDM Chapter 10 and BS5400 Part 10.

4.8.4.7 For steelwork elements and welded reinforcing steel in concrete subject torailway vehicle loading, a design stress spectrum for non-standard loading shallbe derived and the steel details assessed in accordance with BS5400, Part 10,

Cl. 9.3.3 to 9.3.5 inclusive, using the fatigue axle load and the axle spacingsgiven in Subsection 4.4. The stress history for the element under considerationshall be derived using the 'Reservoir Method' described in BS5400, Part 10, Appendix F Example 4; the fatigue axle loads and the specific structuregeometry under consideration. A simplified design stress spectrum shall be

provided in a similar format to BS5400, Part 10 Fig.13 and subject to the

approval of the Corporation.

4.8.5 DESIGN FOR FLOTATION

4.8.5.1 Underground structures shall be designed for flotation loads. If the netdownward load (NDL) at Construction, Operational or Extreme stage is negative,the structures shall be positively held down by an acceptable means which

provides the required restraining forces against uplift. The downward loads inConstruction, Operation and Extreme stages are load combinations to beconsidered in assessing the safety against flotation. The construction

combination shall include, but not be limited to, the main construction and thecase of an excavation over the structure at a later date.

4.8.5.2 The NDL and Uplift are defined by the following equations:

i) NDL = Σ Factored Downward Loads – Buoyancy

ii) Uplift = - NDL (if NDL < 0)

In calculating the NDL, the characteristic downward loads shall be divided byappropriate factors of safety to reflect the uncertainty in the loads. Unless other factors can be shown to be more appropriate, the factors for downward loads in

Table 4.8.5.T1 shall be used. The buoyancy shall be calculated according toSubsection 4.4.9.

4.8.5.3 Adequate factors of Safety against uplift at each of the Construction,Operational and Extreme stages shall be achieved in the design. The factor of

Safety against uplift is defined by the following equation:

i) Factor of Safety = Σ Restraining Forces / Uplift

The Factors of Safety shall not be less than the factors of safety for restraining forces in Table 4.8.5.T2.






4.8/6

Table 4.8.5.T1 Factors of Safety for Downward Loads

Stages

Downward Loads Construction Operat ional Extreme

Self weight 1.03 1.10 1.03

Superimposed DL 1.03 1.10 1.03

Backfill 1.20 1.30 1.03

Table 4.8.5.T2 Factors of Safety for Restraining Forces

StagesRestraining Forces Against Uplif t Construct ion Operational Extreme

Friction effects 1.75 3.00 1.03

Tension piles 2.00 3.00 1.03

4.8.5.4 In calculating the restraining forces, consideration shall be given to thepossibility of the introduction of sliding interfaces during construction. These

include, inter alia, the following:

i) waterproof membrane;ii) temporary works interface; andiii) a bentonite layer on the face of diaphragm walls.

4.8.5.5 An allowance shall be made for the possible reductions in both of thefollowing:

i) average depth of backfill of 0.5m over the roof due to future

construction; andii) the top 2m high portion of diaphragm wall immediately below ground

surface due to future utility work.

Anchors Resisting Structure Flotation Forces

4.8.5.6 The use of permanent anchors to resist flotation forces will generally not bepermitted. However, where the base slab of the structure is founded on rock itmay be economic to use permanent rock anchors or an adequate mechanical

key into sound rock to resist a portion of the flotation forces. Where other methods are shown to be impractical, rock anchors may be allowed providedthey comply with the criteria given in Cl. 4.8.5.7 to Cl.4.8.5.8 inclusive. For structures with developments above, Buildings Department’s approval will alsobe required.






4.8/7

4.8.5.7 For Cl. 4.8.5.6 to 4.8.5.9 rock shall be defined as material which may only beexcavated using robust mechanical means or drill and blast methods. For thepurposes of the NWDSM rock shall normally mean Grade I, II or III material asdefined in Geoguide 3.

4.8.5.8 If approval by the Corporation is given for rock anchors, they shall not protrudebeyond the plan area of the structure. The detailing of anchors and surroundingstructures shall include provisions for access for long term load monitoring,corrosion monitoring and replacement. The design of anchors shall be in

accordance with Subsection 4.6 and the design shall provide sufficientredundancy in the provision of anchors to enable anchor replacement to besafety and efficiently undertaken.

4.8.5.9 Where there are both economic and technical justifications for permanent rock

anchors, full details of proposals shall be submitted for the approval of the

Corporation. In addition a detailed materials and workmanship specificationand method of measurement for such work shall be submitted. The

specification shall include, inter alia, the highest standard of corrosionprotection for both tendons and anchorages; provision for testing duringconstruction and during the Design Life of every anchor by lifting points andadequate clearance; and the requirement for Contractors to provide full

suppliers details of the anchors, such as assumptions, forces, serial numbersand type. The design shall also provide sufficient redundancy in the provisionof anchors to enable anchor replacement to be safely and efficiently undertaken

4.8.6 DESIGN FOR DURABILITY - STEELWORK

4.8.6.1 In certain applications it may be appropriate to permit corrosion of steel platesections by providing additional steel thicknesses for each face according to the

expected exposure. In the absence of any accurate determination, it shall beassumed that the rates of metal loss on each face are as given Table 4.8.6.T1.

Table 4.8.6.T1 Metal Loss

Exposure Rate (mm/year)

Sections permanently below 'non-aggressive' ground

and water concurrently

0.03

Sections permanently below 'aggressive' ground and

water concurrently

0.05

Notes : 1) All other steelwork sections are to be fully protected againstcorrosion for the design life of the structure.

2) See Subsection 4.2 for definition of 'non-aggressive' and'aggressive' water and ground.

4.8.6.2 Steelwork shall be galvanised or metal sprayed, and painted with a system

providing 15 years protection to first major maintenance. Elements subject to






4.8/8

impact such as handrailing should be painted with a system providing 10 yearsprotection to first major maintenance. Further guidance is found in BS EN 1SO12944.

Hot works at site shall be avoided. If site welding cannot be avoided steelworkshould not be galvanised.

4.8.7 DESIGN FOR DURABILITY - CONCRETE

Concrete Strength

4.8.7.1 Designs shall generally specify and be based on the classes of concrete given

in Table 4.8.7.T1, taking into account the particular application and exposurecondition of each structural element. Allowable concrete strengths and

concrete durability requirements for different exposure conditions are defined inTable 4.8.7.T2.

4.8.7.2 Concrete classes in Table 4.8.7.T1 are expressed in terms of characteristicstrength and maximum aggregate size in accordance with the Material andWorkmanship Specification requirements for example:

Class of Concrete 40/20

Characteristic strength (28-day) 40 N/mm2 Maximum aggregate size 20 mm

Table 4.8.7.T1 Concrete Classes

Class of Concrete Characteristic Strength(28-day) N/mm2

20/20* 20

30/20+ 30

40/20 40

50/20 50

60/20 60

* = Not allowed for structural applications+ = Only allowed in moderate exposure condition

Steel Bar Reinforcement

4.8.7.3 The characteristic design strengths of steel bar reinforcement shall be inaccordance with the following, as appropriate:

- “Hong Kong Code of Practice for the Structural Use of Concrete”,

Section 3.2.3, Table 3.3






4.8/9

- HKSDM Chapter 4, Clause 4.2.7- CS2 Construction Standard for Steel Reinforcing Bars for the

Reinforcement of Concrete, Table 2- BS4482 Specification for Cold Reduced Steel Wire for the

Reinforcement of Concrete, Clause 12.1.2.

In addition, the use of deformed bars in reinforced concrete cast bydisplacement of bentonite slurry is mandatory.

Concrete Properties

4.8.7.4 Design values for the following properties of concrete shall be in accordancewith Subsection 4.2 of the HKSDM:

i) early strength gain;

ii) elastic modulus;iii) shrinkage;iv) creep; and

ii) coefficient of thermal expansion.

Reinforced Concrete Nominal Cover and Notional Crack Width

4.8.7.5 Details of the nominal cover to the outermost reinforcement bars and notional

crack width limitations shall be considered for each combination of concreteclass, exposure condition and structural element.

4.8.7.6 In choosing the nominal cover for a structural element, consideration shall be

given to the method of construction, the practicality of achieving the cover, andthe consequences of insufficient cover being provided.

4.8.7.7 The nominal cover requirements shall be specified on all reinforcementdrawings and a note detailed on the general notes drawing stating that:

"The actual cover shall be not less than the nominal cover minus 5mm or theadjacent bar diameter whichever is greater."

4.8.7.8 The nominal cover shall be not less than the appropriate value in Table 4.8.7.T2

for the most critical relevant exposure condition in either the long-term or

temporary case. The nominal concrete cover requirements noted in Table4.8.7.T2 shall be used in the design of all reinforcement. Where structuralelements are required to have a specific Fire Resistance Period (FRP), thenominal cover shall be not less than the most onerous requirements of “Hong

Kong Code of Practice for the Structural Use of Concrete” or the Code of Practice for Fire Resisting Construction, whichever is appropriate to thestructural element being considered.

4.8.7.9 A minimum of 100 mm of cover shall be provided to the surfaces of ducts,

tendons, or wires in prestressed concrete elements into which external fittingsare likely to be made.






4.8/11

Table 4.8.7.T2 Concrete Durabil ity Requirements for PermanentStructures

Nominal Cover (mm)

Concrete GradeExposure

ClassConditions of Exposure

DesignCrack

Width

(mm) 30 40

45

and

over

1 Mild (1) Internal concrete surfaces.

(2) External concrete surfaces protected from

the effects of severe rain or cyclic wetting

and drying e.g.

(a) concrete finish with mosaic tiles,

(b) painting or rendering.

(3) Concrete surfaces permanently under water-

not sea water

0.3

0.3

0.3

35

35

35

30

30

30

25

25

25

2 Moderate (1) Concrete surfaces fully sheltered againstrain or sea-water spray e.g.

(a) surfaces protected by water-proof

membrane

(b) internal concrete surfaces exposed to

(2) Concrete surfaces continuously under

water with a PH > 4.5, or rarely dry

0.25

0.25

35

35

30

30

25

25

3 Severe (1) Exposed to driving rain

(2) Subject to alternate wetting and drying

e.g.

(a) bridge deck soffits

(b) buried parts including underside of

structure resting on layer of blinding

concrete not less than 50mm thick(3) Water Retaining Structures

0.25

0.25

0.2

45

45

45

35

35

35

30

30

30

4 Very

Severe

(1) Directly affected by sea water spray e.g.

concrete adjacent to the sea

0.15 N/P N/P 75

5 Extreme (1) Exposed to abrasive action by seawater

(2) Exposed to water with a pH 4.5≦

(3) Underside of structures in contact with

ground

0.10

0.10

0.25

N/P

N/P

75

N/P

N/P

75

75

75

75

Notes: 1) N/P = Grade not permitted in this exposure condition.2) Cover for crack width design check for all elements shall be 40 mm or

the nominal cover, whichever is less, from the outermost bar.

3) Where elements comply with more than one description, the mostonerous shall be adopted.4) Nominal cover to segmental tunnel lining reinforcement may be

reduced to 40 mm

5) Concrete in exposure conditions requiring minimum grade 45 shouldcontain condensed silica fume unless other measures are implemented.

6) Water retaining structures referred to here are water tanks and the likeused in general building works and not meant to include large civilretaining structures.






4.8/12

4.8.7.13 Diaphragm walls / barrettes and piles shall have a notional cover of 95mm and80mm respectively and a notional crack width of less than 0.3mm. In any casethe structural elements subject to aggressive ground or aggressive water, therequirement as stipulated in Table 4.8.7T2 and additional durability measures in

accordance with Subsection 4.2.9 shall be considered to enable the structuresto achieve the specified design life. For definition of 'aggressive' ground or 'aggressive' water see Subsection 4.2 of this Manual.

Early Age Thermal and Early Age Shrinkage Cracking

4.8.7.14 Reinforcement bars which are provided to resist early thermal and shrinkagecracking shall be uniformly distributed around the perimeter of the concretesection and placed at not more than 150 mm centres. In addition the

reinforcement bars shall be detailed in the layer nearest the surface.

4.8.7.15 Notwithstanding the HKSDM requirements for early age thermal and shrinkagereinforcement, the minimum area of distribution reinforcement to be provided atany section susceptible to shrinkage or early thermal effects shall be 0.4% of

the surface zone, which shall be assumed to be the outermost 250 mm of thecross-sectional area of the concrete element under consideration.Reinforcement provided for other purposes, such as flexural reinforcement, maybe taken into account for the purpose of this check.

Long-term Shrinkage

4.8.7.16 Notwithstanding the shrinkage design requirements contained in the relevantCodes of Practice, allowance shall be made for long-term shrinkage induced

stresses in continuous structures such as those where the distance betweenmovement joints is greater than 15 m. These stresses shall be combined withthe other permanent load effects where there is external restraint, such as soilfriction or structural continuity, which causes these stresses to be locked in.

Creep

4.8.7.17 Concrete creep effects shall be taken into account in all structures. Particular care shall be taken in long span bridges or where live loading is small in

comparison with dead load. For example; in above ground station cantilever roofs and in some areas of plant rooms, special care shall be taken in the

design to ensure creep deflections will not affect the durability of the element or cause problems with any attached items. See also Cl.4.8.6.28 and 4.8.6.29.






4.8/13

4.8.8 PRESTRESSED CONCRETE STRUCTURES

General

4.8.8.1 Prestressed concrete structures shall comply with the relevant parts of Subsections 4.8.2 , 4.8.3 and 4.8.4.

4.8.8.2 Prestressed concrete bridge elements shall be classified in accordance with

“Hong Kong Code of Practice for the Structural Use of Concrete” CI.12.1.3 withrespect to flexural and tensile stress limitations. When applying the loadcombinations, the general requirements of Chapter 2 of HKSDM shall applyexcept that Class 1 shall be applied for load combination 1 and Class 2 for allother load combinations.

4.8.8.3 Other prestressed concrete structures shall be classified in accordance with

“Hong Kong Code of Practice for the Structural Use of Concrete” CI.12.3.4.3with respect to flexural and tensile stress limitations. Structural elements whichare exposed to the weather shall be designed using Class 1 limitations.

Structural elements that are fully protected from the weather may be designedas Class 2.

Prestressing Steel Strength

4.8.8.4 The characteristic strengths and other design parameters for prestressing bars,wire, and strand shall be in accordance with the following standards, asappropriate:

- “Hong Kong Code of Practice for the Structural Use of Concrete”Cl.12.1.8.2

- BS4486 Specification for Hot Rolled and Processed High Tensile AlloySteel Bars for the Prestressing of Concrete

- BS5896 Specification for High Tensile Steel Wire and Strand for the

Prestressing of Concrete.

Prestressed Concrete Materials

4.8.8.5 The post-tensioning system design shall be based on a single proprietarysystem which has been demonstrated to provide; electrical isolation of cables,

anchorages and couplers from the surrounding concrete and bar reinforcement;corrosion resistance; durable non-metallic sheathing, coupler sheaths, trumpets,vents and will enable vacuum assisted grouting to be used as required by the

Materials and Workmanship Specification.

4.8.8.6 Prestressing anchorages shall be detailed such that they are easily accessiblefor inspection and maintenance unless specific protection measures shall bedesigned to ensure that the design life is achievable without maintenance.

Anchorages shall not be detailed in the external face of any externally exposedstructure without suitable waterproof and shall be detailed to prevent theaccumulation of water and dirt around the anchorage.






4.8/14

4.8.8.7 Non-shrink grout shall be used for grouting of post-tensioned tendon ductscross-referenced to the appropriate clause of the Materials and WorkmanshipSpecification.

4.8.8.8 In each section of the structure, one strand of each prestressing cable shall beleft projecting from the anchorage and a copper cable with a cross-sectionalarea of 70 mm2 brazed to the strand or fixed to the anchor head shall passthrough the anchorage cap to permit connection to the stray current collection

system.

4.8.8.9 Consideration should be given to specifying spare ducts which may be usedduring the construction.

Prestressing Data

4.8.8.10 Grouting trials shall be specified for each post-tensioned system and geometryused within each Contract. The number and details of grouting trials shall be

shown on the Tender and Contract Drawings.

4.8.8.11 All assumptions made in the determination of the design prestress loads andresulting extensions shall be included on the Tender and Contract Drawings. As a minimum the following shall be shown:

i) tendon curvature;ii) friction and wobble coefficients;iii) wedge draw-in;iv) initial prestress;

v) cross-section and mechanical properties of strand and concrete section;vi) assumed concrete age at time of transfer; andvii) whether single or double end tensioned.

4.8.9 Reinforced and Prestressed Concrete Detailing

General

4.8.9.1 All detailing of reinforcement shall be in accordance with BS8666: “Scheduling,Dimensioning, Bending and Cutting of Steel Reinforcement for Concrete”, and

shall take into consideration the requirements for durability given in “Hong KongCode of Practice for the Structural Use of Concrete” Cl. 2.1.6.

4.8.9.2 The principal design codes for concrete structures (“Hong Kong Code of Practice for the Structural Use of Concrete”) include requirements for thedimensioning and detailing of reinforcement and prestressing. The majority of these requirements are to ensure structural efficiency of the reinforcement.

Therefore to aid buildability, the UK Concrete Society's Standard Method of Detailing Structural Concrete shall be complied with to ensure detailingconsistency and that structures are easy to construct. Particular attentionshould be paid to the following sections:






4.8/15

i) Paragraph 2.1 - Generalii) Chapter 4 - Detailing and Schedulingiii) Chapter 5 - Structural Elements.

Detailing Requirements

4.8.9.3 In addition to the general principles stated in Cl.4.8.8.1 and Cl.4.8.8.2 thefollowing specific requirements shall be adopted:

i) All laps and couplers shall be staggered unless it can be shown to thesatisfaction of the Corporation that it is impracticable to do so. In caseswhere the staggering of laps can be shown to be impracticable,particular care shall be taken to ensure that lap lengths are increased in

accordance with the requirements of the relevant code of practice.

In concrete members designed to accommodate axial tension forces, nomore than 50% of bars shall be lapped or connected at any one section.The distance between the ends of adjacent lapped bars or connectors

shall be at least 0.5 m.

ii) Mechanical couplers should be considered for large diameter bars inconcrete members subject to axial tension where this is practical andcost-effective.

iii) The minimum clear distance between reinforcement bars or groups of bars (i.e. at laps) shall be 50 mm for aggregates sizes of 20 mm or lessand 75 mm for concrete made with aggregate sizes greater than 20 mm.This supersedes the requirements of “Hong Kong Code of Practice for

the Structural Use of Concrete” Cl.8.2.

iv) Bent bars which are located between concrete faces shall be detailedsuch that the permissible cutting, bending, and dimensional tolerancescan be accommodated without impinging on the nominal concrete cover.

v) The quantity of reinforcement detailed shall be the minimum required bystructural or other design parameters. The requirements for curtailmentof bars shall be in accordance with the relevant code of practice,

balancing these with the need for simplicity and clarity in the

reinforcement drawings and bending schedules.

vi) Maximum use of mid-range diameter reinforcement should be made.

vii) Distribution or early age thermal/shrinkage crack control reinforcementshall be detailed on the outside of the main flexural steel. Thisfacilitates fixing and gives more effective control on surface cracks.

viii) The detailing and the necessity for the provision of shear reinforcement

shall be carefully considered particularly in slabs and walls as this oftencauses congestion and difficulties in fixing.






4.8/16

ix) Shear link reinforcement in all structural elements, except slabs, shall beprovided with closed ends to maintain confinement to mainreinforcement to ensure structural ductility of members. Closed endsshall consist of 135 degree hooks with the bar extending beyond the

end of the hook into the body of the structural element for a full linkanchorage length in accordance with “Hong Kong Code of Practice for the Structural Use of Concrete” or as appropriate - refer to Fig. 4.8.9.F1.

x) Reinforcement detailing and provision to ensure adequate ductility shall

be provided in beam and column frame members in accordance withthe details set out in Fig. 4.8.9.F1 and Fig. 4.8.9.F2. Particular attentionshall be paid to the provision of shear links in the following areas:

a) the top and bottom of columns over the plastic hinge zone;

b) both ends of beams over the plastic hinge zone; and

c) around column vertical reinforcement where the column passesthrough beams/slabs.

4.8.9.4 Where complex or congested reinforcement arrangements cannot be avoided,

(e.g. at beam/column connections, corners, prestressed anchorage zones andthe like), large-scale detailed drawings and sketches shall be prepared todemonstrate that the bars can be fixed without prejudicing the nominal cover and bar spacing requirement and as an aid to construction.






4.8/18



Section 4: Civil Engineering D/MTRC/NW/DSM/ST/409/A54.9 Drainage


4.9/1

4.9 DRAINAGE

4.9.1 SCOPE

4.9.1.1 This subsection includes Civil Engineering and Building drainage designrequirements for the following:

i) drainage system design and construction details within structure trackareas in tunnels, bridges, viaducts, ancillary buildings and stations(excluding under platform voids);

ii) drainage system design and construction details for external catchmentareas within the Site boundaries;

iii) construction details only for Building Service foul and surface water

pumped and gravity drains external to the building envelope (such as pipetype, pipe supports/bedding, catchpit, and chamber details and the like) inaccordance with the drainage system design requirements identified inSection 7 of the NWDSM (such as falls, pipe/sump size, location,manholes and the like); and

iv) construction details only for Building Service pumped and gravity sumps,tanks, channels, and openings in buildings in accordance with thedrainage systems design requirements identified in Section 7 of theNWDSM.

4.9.1.2 Trackform drainage design requirements other than those given in Cl.4.9.1.1

shall be in accordance with Section 3 of the NWDSM.

4.9.1.3 Building service drainage design requirements shall be in accordance withSection 7 of the NWDSM. Building service drainage includes:

i) internal and external building foul and surface water drainage systemdesign (including roofs and internal slabs) and internal building drainageconstruction details only. System design requirements includes bothpumped and gravity drainage through to the outfall at externalculverts/channels/nullahs and the like (such as pumps, falls, pipediameters, sump sizes, pipe, and manhole locations and the like);

ii) design and specification of tanks and sumps within areas identified above;

iii) water supply system design; and

iv) puddle flange design within building walls for outgoing pipework.





4.9/3

vi) specific drainage from E&M equipment;

vii) water from tests on fire systems;

viii) discharge of waste water prevention cisterns over urinals (whereprovided);

ix) discharge of toilet cisterns;

x) discharge through wash hand basins;

xi) discharge from Mess Room sink;

xii) discharge from Cleaner's Room sink;

xiii) leakage from services; and

xiv) effluent discharge from maintenance activities in depots.

Surface Water, Groundwater and Foulwater Drainage System

4.9.2.6 The Corporation wishes to minimise the provision of external drainage systemsand to maximise the use of the DSD drainage systems. In addition, in order tominimise operating costs the use of gravity as opposed to pumped drainagesystems is preferred.

4.9.2.7 Unless stated otherwise, separate collection and discharge systems shall beprovided for the drainage of surface water, groundwater and foulwater. Inaddition separate drainage systems shall be provided in stations, ancillary

buildings and that arising from tunnels. Disposal shall be effected by one of thefollowing separate systems:

i) surface water and groundwater by gravity into the public stormwater drainage system except sea overtopping water which shall be by gravityinto the sea;

ii) surface water and groundwater pumped to the public stormwater drainagesystem;

iii) foul drainage by gravity to the public foul sewer; and

iv) foul drainage by pumping to the public foul sewer.

4.9.2.8 Surface water and groundwater drainage systems shall be provided withstandard terminal manholes, near the site boundary immediately before theconnection to the public stormwater drainage system. These terminal manholesinclude sump, silt trap and rodding holes and the like.

4.9.2.9 Foulwater drainage systems, other than those carry discharges from sanitary





4.9/4

fitments, shall include an oil interceptor for the treatment of all foulwater beforeany connection to the public storm sewer.

4.9.2.10 Surface water and groundwater may be discharged into a stormwater soakaway

or to a water course. The approval of the relevant authority must be obtained for the proposed means of disposal. When the surface water or groundwater isdischarged into a stormwater drain there shall always be a gravity fall in theconnection pipes and the fall shall be sufficient to give protection from anysurcharging that may occur in the drain. Non-return flaps are not to be reliedupon to give protection against surcharge in any situation.

4.9.2.11 Drains shall follow the shortest practicable route to the stormwater drain, soakaway,or watercourse. If the required velocity head or the protection against surchargecannot be obtained by gravity, then pumping must be provided and the dischargearranged in a manhole or a chamber so that the necessary gravity fall is obtained.The guiding principle in the location of manholes is that they shall be situated so as

to allow every length of drain to be accessible for cleaning and testing. On straightruns the maximum distance between manholes shall be 50 m.

4.9.2.12 Apart from the collection of leakage, condensation, track washdown water andthe like, each separate structure trackform or building invert shall not be used asan open channel system to carry flows, either to the nearest sump for disposal,or from other trackform areas or drainage systems.

4.9.2.13 Groundwater drainage systems shall be kept separate from surface water drainage systems in order to prevent the surface water discharging water into thegroundwater system and hence into the ground.

4.9.2.14 Foulwater discharge from maintenance activities within depots will requiretreatment or neutralization to satisfy EPD standards for effluent discharge prior todischarge to the public foul sewer.

Drainage from Developments above Stations and Ancillary Buildings

4.9.2.15 All drainage systems for developments above stations and ancillary buildingsshall be designed in accordance with the Buildings Ordinance and BuildingRegulations. They shall be kept entirely separate from the station/buildingdrainage system and shall not penetrate the station/building box. The drainagesystem shall be designed to prevent a build up of water above the slabseparating the development from the station/building under adverse conditionssuch as power failure, blocked drains or fire. Provision shall be made for easyaccess for inspection and maintenance of the drainage systems of developmentssuch that access through the station/building is not required. The station/buildingroof slab and movement joint shall be protected against water leakage bywaterproofing membrane.





4.9/5

Interception of Land Drains

4.9.2.16 In no circumstances shall an open ditch be cut along the top of the slopes of acutting. Where a new cutting encounters a ditch or drain liable to carry any

appreciable volume of water, the flow shall be intercepted in a manhole built asnear to the Railway Boundary as possible and shall be led away in close jointeddrains.

4.9.2.17 Small springs or land drains, which cannot be diverted in the manner described inCl.4.9.2.15, shall be intercepted by stoneware, vitreous clay, or concrete pipesbedded in concrete. The water shall be carried down the slope by means of close

jointed pipes or precast concrete channels with covers bedded on concrete for collection in trackside drains. The channels shall feed directly into the track draincatch pits where the silt shall be trapped.

Ditches and Drains at Toes of Embankments

4.9.2.18 Ditches or drains at the bottom of embankments shall be installed as far from thetoe of the bank as is practicable.

4.9.2.19 At the foot of an embankment provided with a retaining wall, an open jointed drainor ditch shall not be installed unless this can be positioned at a distance from thefoundation which will avoid endangering the stability of the wall. If a closer positionfor the drain is unavoidable it shall consist of a channel drain.

Precautions Against Slope Failures

4.9.2.20 The design of drainage in deep cuttings or embankments where slips are known to

have occurred or where there is reason to anticipate their occurrence, shall payparticular attention to the geotechnical stability considerations - refer to Subsection4.6. Wherever possible all drainage systems shall be kept away from and out of slopes. Where this is not possible then appropriate protection against leaking or failure of such systems which could affect the slopes shall be provided.

Pipe Penetrations

4.9.2.21 Pipe penetrations through fire barriers shall be avoided wherever possible.Where pipes are required to pass through a fire compartmentation barrier, thepossibility of fire damage to the pipe causing a breach of the fire separation shallbe considered. Appropriate pipe materials, casings or other measures shall be

adopted to prevent this breach.

Close Jointed Drains

4.9.2.22 All close jointed drains shall be jointed with a patent joint and shall be bedded inconcrete of a width 300 mm greater than the internal diameter of the pipe,extending at least 75 mm above and below the pipe.





4.9/6

Channel, Tank and Sump Protective Coating Materials

4.9.2.23 To prevent capillary rise of contaminated water all internal surfaces of reinforcedconcrete tanks, drainage channels, tunnel manholes, and drainage sumps shall

be coated with either:

i) a two coat, 400 micron Dry Film Thickness (DFT) damp-tolerant epoxy-coating system; or

ii) a two coat 2 mm thick polymer modified cementitious waterproofingmaterial.

4.9.2.24 Where drainage channels are adjacent to walls, the lower 300 mm of the wallsshall also be coated with the epoxy coating or polymer modified cementitiouswaterproofing material. Refer to Fig. 4.9.2.F1.

4.9.3 DRAINAGE WATER VOLUME ESTIMATION

Rainfall Design Return Period

4.9.3.1 Surface water drainage shall be designed for a 1 in 200 year return period rainfallevent. However, where flooding would result in loss of life or serious damage toinstallations, the adoption of a higher return period should be considered.

Small Catchment Peak Discharges

4.9.3.2 For roofs, urban areas, and relatively small catchments in rural locations

(typically less than 100 ha), design peak discharges may be estimated using theRational Method in accordance with Section 7 of the HKSWDM.

Large Catchment Peak Discharges

4.9.3.3 The estimation of design peak discharge for catchments larger than 100 ha,where the Rational Method is not applicable, shall be by rigorous methods to beproposed for the approval of the Corporation.

Design Sea Levels

4.9.3.4 For determination of design sea levels, a 0.5m additional height shall be added

to the extreme design sea levels for Hong Kong, which are available in theHKSWDM, to allow for long term climatic change where this is more onerous for the case being considered.

Seawall Overtopp ing Water

4.9.3.5 Where the Railway may be affected by overtopping of an adjacent seawall, adrainage system shall be provided immediately inside the Railway Boundary.





4.9/8

Notes: 1) Class of watertightness are defined in Subsection 4.2.

Condensation Water

4.9.3.10 The flow of surface water generated by condensation shall generally be ignoredwhen calculating flows and sump sizes, except where these are associated witha particular item of E&M plant, such as:

i) cooling coils of air handling units;

ii) chilled water pumps;

iii) fire pumps; and

iv) package air conditioning units.

Washdown water and Fire System Tests

4.9.3.11 There shall be sufficient number of outlets on platforms and concourses to collectand dispose of washdown water and water from fire system tests.

4.9.3.12 Track washdown water from one washdown vehicle shall be allowed for, thisvehicle shall be assumed to discharge a maximum of 25,000 litres (25 m3) evenlyover 1 km of track in 1 hour. Consideration shall be given to a single track beingwashed or adjacent tracks where this would be more onerous for the structureunder consideration.

Drain Blockage

4.9.3.13 The effects of flooding as a result of a partial blockage of drains shall beconsidered with a view to limiting and restricting the extent of any resultingflooding and damage to property and life.

4.9.4 DRAINAGE SYSTEM - HYDRAULIC ANALYSIS

Introduction

4.9.4.1 For the purposes of sizing drainage structures, a design sea level with a 10 year

return period in conjunction with a rainstorm of 200 year return period shall beassumed. The design capacity of drainage systems shall also be verified under extreme sea level of 200 year return period in conjunction with a rainstorm of 10year return period.

Maximum Velocity

4.9.4.2 The maximum velocity at peak flow shall not exceed 5-6 m/sec in order to avoid





4.9/10

Notes: 1) 'Long term ground movement' is dependent upon foundationmaterial and embankment heights.

2) 'Degradation allowance' is to cover loss of material between

embankment maintenance intervals.3) 'Velocity head' will be small in the tidal reaches, but could be

considerably higher in the steep reaches. This provision isrequired to allow for local velocity head recovery (e.g. atstructures).

4) 'Superelevation at bends' and standing waves at transitionsmay be significant in the upper reaches. Local provision shallbe made to accommodate these.

5) 'Safety margin' is an allowance to provide public confidence inthe system when defences are operating at their designcondition. For hard defences (e.g. concrete walls), 300 mm isgenerally considered adequate. However, for soft defences

(e.g. earth embankments), a more generous provision (500 mm)is appropriate.

4.9.5 STATION AND ANCILLARY BUILDINGS

General

4.9.5.1 Building’s foulwater system design shall comply with the requirements of theBuildings Ordinance and Building Regulations. The building foulwater systemshall provide a separate system of self cleansing pipework to remove the wastespeedily without risk of nuisance or danger to health. The system shall be as

simple and direct as possible. No building foulwater waste shall be dischargedinto track or tunnel drainage systems.

4.9.5.2 The foulwater from underground buildings shall be dealt with by a separatesystem, comprising collecting pipes, vented tanks/sumps, and pumps, to connectto the public foul sewage system at street level.

4.9.5.3 The foulwater from surface and above ground buildings shall be disposed of by anormal gravity system.

4.9.5.4 The criteria for determination of the number of sanitary fittings within buildingswhen designing the foulwater drainage are given in Section 5 of this Manual.

4.9.5.5 The drainage system shall be designed to prevent surface water or foulwater from buildings being carried down the running tunnels to the lowest point linesumps.

4.9.5.6 A covered washdown water and groundwater seepage drainage channel shall beconstructed at the mouth of each running tunnel as it enters a building. Thechannel cover shall be flush with the surface of the building base slab and the





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track bed in the tunnel shall be level with it, such that passenger emergency walkthrough is achieved without a step.

4.9.5.7 In cases where tunnels are on a down gradient into a building, the building sump

may be sized to accommodate the groundwater seepage and washdown water flow from the tunnels in addition to the flow from the building.

Floor Cleaning and Surface Drainage

4.9.5.8 In public areas which are accessible by floor cleaning machines, typicallyconcourses, platforms and adjoining passageways at the same level, surfacedrainage connected to the foulwater system shall be provided in the form of drainage outlets with covers at strategic locations, to drain off any accidentalspillage or dripping from water sources such as all fire hose reels and water supply points as defined by Section 5 of the NWDSM. Drainage channels shallnot be installed in these public areas.

4.9.5.9 In public areas which are not accessible to floor cleaning machines, typicallyentrances and passageways, surface drainage shall be provided in the form of dish drainage channels formed within the finishes depth, adjacent and parallel tothe passage walls and shall incorporate drainage outlets connected to thefoulwater system.

4.9.5.10 Drainage outlets in the areas defined in Cl.4.9.5.8 and Cl.4.9.5.9 shall beinstalled at not more than 25m centres.

4.9.5.11 In non public areas, dish drainage channels are not required. The requirementsfor drainage provision in specific rooms, including room sumps and room oil

interceptors, shall be as specified in Section 5, Section 7 and Section 8 of theNWDSM.

Drainage Falls

4.9.5.12 Drainage falls within stations and ancillary buildings shall be as follows:

i) Platforms

A 1 in 100 fall between the platform edge and the column line, away fromtrack, shall be provided. The area between the columns shall remain level.

ii) Concourses

Concourses shall be level.

iii) Plant rooms

Generally level with positive drainage provided to specific items, as required.





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iv) Entrance passageways

A minimum 1 in 100 longitudinal fall at intermediate landings between flightsof stairs. Elsewhere, passageways may be level if there is no requirement

for a ramp to achieve passenger routing.

v) Escalator machine rooms

A minimum fall of 1 in 100 to suitable outlets.

vi) Under-platform voids

A minimum 1 in 100 fall to drainage outlets as shown on Figs. 4.9.5.F1 and4.9.5.F2. For typical track bed, under platform, and escalator pit drainagedetails - refer to Fig. 4.9.5.F1 and Fig. 4.9.5.F2.

4.9.6 TUNNEL, SHAFT AND CAVERN SYSTEMS

General

4.9.6.1 A separate drainage system including line sumps shall be provided to cater for seepage, condensation, track washdown water and any other foulwater that willbe collected from the tunnel trackform and invert. Line sumps shall be sited at or close to the low points of the tunnel, or at a maximum of 2000 m whichever isless.

4.9.6.2 Shafts or caverns shall not generally be provided with sumps unless the layoutprecludes gravity discharge to the line sump.

4.9.6.3 Apart from the collection of leakage, condensation, and track washdown water,each separate trackform or tunnel invert shall not be used as an open channelsystem to carry flows from other trackform areas or drainage systems to thenearest sump.

Portals

4.9.6.4 Surface water run-off from approach structures, surfaces slopes and elevatedsections shall not be permitted to enter the tunnels at portals by the provision of an interceptor drainage channel, a secondary interceptor drainage channel shallbe positioned a short distance into the tunnel to suit the cut-off of wind blown rain.

The interceptor channel shall be made wide enough to effectively intercept water falling towards the channel without the need for interceptor barriers. Where theapproach structure is on a down gradient to the portal a substantial sump shallbe provided to collect water falling on the approach unless this can be pipedaway by gravity. For sizing of any portal sump - refer to Subsection 4.9.8.

4.9.6.5 The design of portal approach structure drainage shall ensure that the invert level





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of any gravity drains from the approach structure are above the flood protectionlevel required in Subsection 4.2 to prevent backflow, the use of non-return tideflaps for this purpose is not allowed.

Ventilation Shafts

4.9.6.6 Provision shall be made at the ventilation shaft terminals to collect the rain water which is blown or falls into the ventilation shaft. Collection shall be by a systemof gutters discharging to the existing surface water drainage system in the locality.The remainder shall be intercepted at concourse or track level depending on the

detailed configuration of the ventilation shafts at individual locations anddischarged to the station foulwater drainage system.

4.9.6.7 The design shall ensure that flood protection at least equal to the requirementsfor station entrances, detailed in Subsection 4.2.

Drainage Fall

4.9.6.8 Drainage fall within tunnel surfaces shall have a minimum fall of 1:100 to drains.

4.9.7 BRIDGES AND ELEVATED STRUCTURES

4.9.7.1 The design and detailing of surface water drainage for bridges shall conform withthe general requirements of the NWDSM and Chapter 16 of the HKSDM.

4.9.7.2 Where bridges or elevated structures support sections of track with less than 1%longitudinal fall, the track supporting elements shall be designed with imposed

localised longitudinal falls of no less than 1%, without the use of screeds. Theefficiency of the drainage system shall take into account the presence of trackform which may impede the drainage path.

4.9.7.3 To avoid flooding on bridges in the event of a blockage in the main drainagesystem, emergency overflow pipes shall be provided. These pipes shall be100 mm diameter and project above the concrete invert by a nominal 25mm -refer to Fig, 4.9.7.F1. The pipe spacing shall be at similar spacing as the viaductdrainage gullies. Wherever possible, emergency drain-pipes shall not be locatedabove highways or areas to which pedestrians have unrestricted access.

4.9.7.4 With the exception of the emergency overflow pipes and superstructure voiddrains, all bridge surface water drainage including those provisions withinabutment galleries and beneath structure movement joints shall be positivelyconnected to the public storm water drainage system via a terminal manhole.

4.9.7.5 Due to the structural arrangement and spatial restriction of bridges, surface water drainage and foulwater drainage may be collected and discharged in a combinedsystem, subject to the approval of the Corporation. The combined drainage shallbe connected to the public storm water drainage system via an oil interceptor,





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with bypass protection for high flows.

4.9.8 BUILDING, LINE AND PORTAL SUMPS

4.9.8.1 The normal capacity of surface water or foulwater sumps shall be defined as thevolume between the minimum water level at which the pumps are switched off automatically and the upper level, at which the final duty pump switches on.They shall be sized to ensure a minimum pump running time of 5 minutes. Thenormal capacity of the sump should be small enough to ensure at least one startof the pumps per day during wet weather. In no event shall the sump be sized sothat the pumps start more frequently than four times per hour.

4.9.8.2 The alarm level in the sump shall be set just above the top of the normal capacity,to sound an alarm in the Station Control Room (SCR) if the water level in thesump continues to rise above the top pump cut-in level.

4.9.8.3 The sump shall be designed to accommodate four hours inflow above the alarmlevel. This may be reduced to one hour storage capacity in accordance withClause 7.8.2.6.3 (b) but in no case shall the storage capacity be less than thevolume of water expected during track or structure washdown - refer toCl.4.9.3.11 and Cl.4.9.3.12. This arrangement shall also be subject toassessment on case by case basis and will only be approved where civil designconsiderations make larger storage capacities impractical.

4.9.8.4 Sumps receiving large volumes of rainwater may be designed to accommodatethe flow that would occur above the alarm level for the period of time required toinstall emergency pumping measures. This period of time is likely to be

considerably less than four hours required by Cl.4.9.8.3 and would allow for thetime taken for emergency personnel to arrive at the sump and the set up time of the emergency pumping measures, including the discharging of pumped water.This period of time shall be subject to consultation with and the approval of theCorporation.

4.9.8.5 In locations where sumps are not covered by a structural floor they shall becovered with open grille flooring, which shall be removable and flush with theadjacent floor level. Corrosion resistant stainless steel or polymer grill flooringshall be specified. Discharge valves and the manifold shall be installed abovethe grill and the grill shall provide access for inspection and maintenance of thevalves and pumps.

4.9.8.6 Lifting beam or lifting eye and appropriate equipment shall be provided for pumpmaintenance.

4.9.8.7 Wherever practicable direct ladder free access from ground level shall beprovided to the sump, for emergency services use during operating hours, for lifting out injured personnel. This access shall be secure against unauthorisedentry.





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4.9.8.8 Sump maintenance access shall be provided from track level. Vertical ladderswith fall arrest devices, in accordance with Subsection 4.2, shall be provided inany emergency services sump access shafts to enable inspection. However,

these shall be positioned so as not to impede the removal of injured personnel byemergency services - refer to Fig. 4.9.8.F1, 4.9.8.F2 and 4.9.8.F3.

4.9.8.9 In general, surface water drainage system shall be designed for a 1 in 200 year return period rainfall event. However, where large quantity of surface water would result in an uneconomic size of the sump, the adoption of a lower returnperiod should be considered. Such a proposal should be supported by a full riskassessment and shall be submitted for the approval of the Corporation.

4.9.8.10 Sumps shall be installed with screens such that debris within the system cannotcause damage to pump impellers.

4.9.9 CULVERTS

General

4.9.9.1 Where embankments are to be built across existing ditches or small streams,culverts shall be provided. The cross sectional area of the culvert shall be 50%larger than the design flooded cross sectional area of the water course. Allrelevant authorities shall be contacted to determine if there are futuredevelopment proposals that could increase flows.

4.9.9.2 Where multiple pipes or a reinforced concrete culvert is used, all such large

culverts shall be provided with concrete inverts (concrete inlet and outlet aprons),falling in the direction of the flow of the water and extending the full width of thebottom of the embankments, and shall be provided with head walls, wing walls,and parapet walls of sufficient height to fully retain soil from the slopes or excesstrackform ballast material.

Culvert/Open Channel Inspection and Maintenance Access

4.9.9.3 Access points for inspection and maintenance/desilting operations shall beprovided at regular intervals as indicated below.

Type Description Maximum Spacing

1 Desilting Access 100 m2 Personnel Access 50 m

4.9.9.4 The spacing and sizing of access points shall allow for the layout of roads, major buildings, and other constraints as well as maintenance equipment and access tosites.





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4.9.9.5 Adequate silt/boulder inlet structures are required to prevent the ingress of siltand boulders, but not to impede the normal design flows, within culverts andopen channels. Adequate access to inlet structures for desilting andmaintenance shall be provided.

4.9.9.6 All inlet structures shall be fitted with handrailing and stainless steel protectivescreens to prevent accidental access to the inlet structure and culverts duringfloods. Screens shall be designed to reduce head losses and blockage duringfloods and adequate access for cleaning and maintenance shall be provided. A200 mm spacing between the bars of screens shall be adopted.

4.9.10 SURFACE WATER GROUNDWATER AND FOULWATER PUMPS

4.9.10.1 There will be a minimum of two pumps, a duty pump, and a standby. Dependingon the detailed design of the pumping system, more than one duty pump may be

needed.

4.9.10.2 The pumps provided for sumps shall have sufficient capacity to handle all flowsallowing for one failed pump. This will normally require the provision of threepumps.

4.9.10.3 Provision shall be made for the rapid installation of surface water emergencypumping measures and the identification of the nearest entry to stormwater drains suitable for the emergency discharging of surface water sump water.

4.9.10.4 The invert level of the lower end of a culvert shall be slightly higher than the naturalbed of the stream or drain into which it discharges, and sufficient of the existing

stream on both ends of the culvert shall be reconstructed or lined with side wallsand inverts to avoid waterlogging of the foot of the railway embankments.

4.9.11 VIADUCTS

4.9.11.1 The track drainage system shall be designed utilizing only 75% of the designcapacity of perforated pipes. An additional allowance shall be made for thedrainage of ground-water. If appropriate.

4.9.11.2 Where a highway is located on viaduct directly above railway tracks at grade, fullrainfall intensity for the track drainage shall be calculated using a 300 vertical

angle subtended inwards from the edge of expressway decking.

4.9.11.3 For tracks fully covered by highway decking, a nominal pipe diameter of 150 mmshall be provided for each track that is fully covered and not subject to rainfallintensity as defined above.





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4.10 Temporary Works


4.10/1

4.10 TEMPORARY WORKS

4.10.1 SCOPE

4.10.1.1 This subsection specifies the criteria for the design of Temporary Works andthose Temporary Works design criteria which shall be incorporated into theContract. The design criteria shall also be used in assessing all Temporary

Works design submissions made by the Contractor. They have evolved after taking into consideration the construction methods generally used in HongKong and the information about general ground conditions in Hong Kong.Temporary Works shall be designed in accordance with the requirementsstated in the M&W Specifications.

4.10.1.2 The Corporation does not guarantee that by applying the design criteria laid out

in this document, in particular the specified limits, that the Temporary Works willbe safe and adequate or that no damage or settlement will occur toneighbouring buildings or land. These criteria and any approvals given as a

result of them, shall not relieve the designers of Temporary Works from their obligations to ensure that all such works are designed with due regard to safety,and Hong Kong ordinances, to cause no loss or damage to adjoining property,land or the Contract.

4.10.1.3 Some Corporation works are subject to approval of the Buildings Department.In these situations all the obligations of the relevant legislation shall becomplied with by the Contractor.

4.10.2 GENERAL

Envisaged Construction Sequence Drawings

4.10.2.1 A separate set of 'Envisaged Construction Sequence and Temporary Works’drawings shall be produced with the Tender documents in accordance withSubsection 4.2.18. Contractually binding requirements shall be included on the'Construction Constraints Drawings' in the Tender or Contract documentation as

appropriate.

4.10.2.2 Under no circumstances shall the details of temporary works, such astemporary cut slope angles or cofferdam arrangements, be included in thepermanent works tender or contract documentation.

Temporary Works Design

4.10.2.3 All major items of Temporary Works shall be checked by an IndependentChecking Engineer.

4.10.2.4 The temporary drainage which will be used during construction or betweendifferent construction stages, shall be designed on not less than the basis of a 1in 10 year return period. The adoption of a higher return period shall be

considered where loss of life or damage to property could occur.




4.10 Temporary Works

4.10.3 DESIGN INTERFACES WITH EBS

4.10.3.1 The design of the Temporary Works shall limit ground movement generally inand around the site works area and beyond, thereby avoiding damage to

adjacent structures, footways, roads, services, utilities and street furniture.

4.10.3.2 The design of Temporary Works shall ensure that ground movements adjacentto EBS or the Works are within the allowable Risk Categories and their equivalent ground limits for EBS, defined in Subsection 4.2.

4.10.3.3 The design of Temporary Works shall ensure that movement in the adjacentEBS or the Works is not greater than the limits defined in Subsection 4.2. Inzones where EBS, services or utilities are considered to be at risk the Designer shall propose protection measures to mitigate movements.

4.10.4 DESIGN INTERFACES WITH NEW MTR STRUCTURE

4.10.4.1 The design of Temporary Works shall take account of all the applied externalforces and imposed structural deformations. Additionally for undergroundworks, the Temporary Works design shall take due cognizance of the effects of removing the load from the ground and the movement of the groundindependent of the load.

nwdsm section 04 - civil engineering_a5 (18 apr 2013).pdf

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