Landslide Disaster Protection Project of the National Road Network

Project DirectorLandslide Disaster protection project

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MITIGATION OF LANDSLIDE AT NAWALAPITIYA

LOCATION OF LANDSLIDE DISASTERS IN MOUNTAIN AREA

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Source of Finance JICA Rs. 11,423 Million. Government of Sri Lanka Rs. 3331 Million.Total amount Rs. 14754 Million.

This project consists of 16 sites in 3 provinces as follows,8 sites in Central Province2 sites in Sabaragamuwa Province 6 sites in Uva Province

Project is divided into 3 categories as follows, Lot A-6 Sites (ICB) Lot B-10 Sites (LCB) Lot C-Early warning system(30 Location) (LCB)

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Site locations of the Project (Both ICB and LCB)

ICBLCB

ICB and LCB

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Project Objective The objective of the project is to mitigate

landslide disaster in national roads to enhance the security of the road network and safeguard the life of people including road users and residents

To transfer Landslide mitigation knowledge to related parties

Mitigation of Landslide at Nawalapitiya

Gampola – Nawalapitiya road A113-15 km

Rank C Site(ICB)　Landslide A113-015(Nawalapitiya)

Landslide movement

Profile of landslide

Topographic Survey -To produce detailed topographic map and profile

Geological Field Survey -To obtain surface information of Landslide such as tension

crack, compression crack on the ground , crack appears on structures and tilting of trees

Drilling Investigation -To understand underground information by drilling

Geophysical Exploration -To obtain 2-D underground information (Using

Resistivity &

seismic exploration method)

Monitoring of Landslide - To obtain information of landslide activities by surface, subsurface, and groundwater monitoring Landslide Analysis - To identified the landslide blocks, boundaries and slip surfaces

Slope Stability Analysis -To obtain necessary resistance by countermeasure

Selection of Countermeasure -To select optimal set of countermeasures

Detail design -To prepare drawings for procurement of civil works

Flow of Investigation & Design

Result of Topographic and Geological Field Survey

Automated Water Level Gauge

Extensometer

Pipe Strain Gauge

Inclinometer

Direction of movement

Main scarp

Monitoring Equipment fixed at site

For Surface Displacement

For Underground Displacement

For GroundwaterObservation

Pipe stain gauge can provide continuous observation but expensive.

Landside Geological Profile-Nawalapitiya(A113-015)

Countermeasures against Landslide

Control measures Preventive measures1 Surface Drainage control2 Groundwater control • Shallow groundwater control • Horizontal drainage boring • Interceptor under drains • Deep groundwater control Drainage wells3 Earth removal4 Counter embankment (Butters fill )

1 Piles2 Anchor3 Retaining walls

Japanese Ground Anchors Drainage Well Preventive Steel Pipe

Selected Countermeasures for Nawalapitiya Landslide

• Control Measures– Surface drainage – Horizontal boring– Drainage well– Shallow ground water drainage

• Preventive measures– Ground Anchors– Steel Pipe Piles

Proposed Countermeasures at Nawalapitiya

Horizontal Drainage Drilling

Drainage Well

Drainage Well

Drainage well

Concerete bottom lining

Horizontal drainage boring

Discharge boring

Ground water level

Resting place

Drainagewell Horizontal drainage boring

Discharge boring

Pile Work

Ground Anchor Works

Appearance on the surface of ground anchors with loading plates.Ground anchor can be used with crib wall as loading member.

Ground Anchor Works

Fixing length of tendon

Free length of tendon

Free length

Fixed anchor length

Grouting

Loading plate

Protection cup

Antirust oil

Nut

Anchor length

Structure of ground anchor

• Composed of anchor body (fixing length), tension part (free length), and anchor head with loading plate.

• Most effective with the total length of 30 meters or less.

• Applied to landslide and slope failure.Ground anchor with crib wall

Light Weight Embankment with Air Mortar• Can be applied to repair of road shoulder and

road widening in mountainous area.• Formed mortar(or air mortar) or cement can be

used as light weight embankment.• Fluidity of air mortar enables easy

construction. (No need of compaction due to its fluidity). It can be used in backfilling at narrow space.

• Strength and weight can be set by changing mixing proportion. (Strength can be set at 1,000kN/m² or lower whereas unit weight can be between 5 and 13kN/m³.

Light Weight Embankment with Air Mortar

Existing roadDesigned road

Lightweight embankment

5 m

Rock bolt work

Protection by shotcrete Protection by concrete panel

Air mortal embankment shall be protected by concrete panel or shot Crete.

Typical cross section

Countermeasure Proffile

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J1

J2

J3LIGHTWEIGHT

PILE (Ø 406.4,

23.5

L=30.0 m

5°

5°

DRAINAGE WELL(PROJECTED VIEW)

GROUND ANCHOR LINE NO:01VSL E5-5, Td=477.0 kN, Ø 90 mm@ 2000 mm SPACING (29 Nos)

DRAINAGE WELL(PROJECTED VIEW)

t=30mm, N=28)

EMBANKMENT FILL

PROJECTED VIEW

(PROJECTED VIEW)

GROUND ANCHOR LINE NO:01VSL E5-5, Td=477.0 kN, Ø 90 mm@ 2000 mm SPACING (29 Nos)

1:0.

6

4.50

22.018.0

L=81.0 m

23.0

26.0

L=50.77 m

1.0

0.5

L=50.0 m

PROJECTED VIEW

26°30'

26°30'

5°

5°

5°

5°

5°

HORIZONTAL BORING

HWL

FsCase

For C&ø (CWL)

J1 J2 J3

Pile Work

Horizontal Drain(3m WaterTable Reduce)

Road Widening

Ground anchor works

1.000 1.0001

2

3

4

5

1.000

HWL 0.947 0.983 0.996

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1.050

1.199 1.094 1.095

1.203 1.102 1.119

1.271 1.200 1.275

0.983 0.996

Parameter

?(kN/m3)

C'(kN/m2)

F (Degree)

J1 J2 J3

18.0

13.267

15.0

22.869

15.0

25.252

15.0

18.0 18.0

Benefit from the Project Japanese technology against landslide will be introduced.

Safety traffic will be secured at the Project sites.

Local contractors will have knowledge and experience of Japanese countermeasures against landslides

Local engineers will learn design methods of Japanese countermeasures

Local engineers will learn Japanese investigation and monitoring methods

Local authorities will get experience and expertise regarding Japanese guidelines and manuals against landslide and utilize it for improving Sri Lankan guidelines.

In future, similar countermeasures will be established along the highways in Sri Lanka and provide safer roads to the public.

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Thank you

Project DirectorLandslide Disaster protection project

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IF YOU DO NOT TAKE CARE OF SOIL,SOIL WILL NEVER TAKE CARE OF YOU