optimal foundations - iit gandhinagar foundations... · • more than 40 storage tank foundations...

16/10/2015

GITSSI-Lecture-BVM College 1

Singapore Resource Piling Malaysia India Hong Kong Indonesia

Short Course on Geotechnical Investigation for Structural Engineering

15- 17 October 2015, IIT Gandhinagar

Sridhar Valluri, Geotechnical Manager Keller India

Optimal Foundations

Contents

1. Optimal Foundations

2. Over View of Ground Improvement Techniques

3. Case Studies

i. Power Plants

ii. Oil & Gas

iii. Industrial Structures

iv. Real Estate

v. Transportation

4. Conclusions

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Definition: Alternative or approach that best fits the situation, employs resources in a most effective and efficient manner, and yields the highest possible return under the given circumstances.

Optimal Foundation

Opportunities for Optimization

Approaches

• Good data : extensive soil investigation • Physics : how are forces resisted - design • Materials : cost & carbon footprint, waste disposal, availability • Time : how long do you take • Convenience : is the solution flexible, allows change

Examples 1. Power Plants 2. Oil & Gas 3. Industrial Structures 4. Real Estate 5. Power Plant Structures 6. Transportation

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Over View of Ground Improvement Techniques

Foundation Engineering

Shallow Foundations

Foundations on Natural Soils (Un-Improved Soils)

Good Bearing Strata

Less Load Intensity

Settlements within Tolerable Limits

Foundations on Weak Soils (Improved Soils)

Ground Improvement Techniques

Deep Foundations

Bored Cast In-Situ Pile Foundations

Friction Piles

End Bearing Piles

Friction & End Bearing Piles

Driven Pile Foundations

Steel Piles

Pre Cast Piles

Driven Cast In-Situ Piles

Ground Engineering & Foundation Systems

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Principles & Types of Ground Improvement Techniques

Ground Improvement

Open Foundations

Deep Foundations

Ground improvement is defined as the controlled alteration of the state, nature or mass behavior of ground materials in order to achieve an intended satisfactory response to existing or projected environmental and engineering actions.

Source: CIRIA Publication

Concept of Ground Improvement

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• Densification (loose sands) : rearrangement of granular particles

• Consolidation (Cohesive) : drainage and reduction of voids

• Chemical Modification : hardening by addition of binders

• Displace & Reinforce : pushing unsuitable soils aside, installing stiffer elements

Principles of Ground Improvement

Ground Improvement

Densification

Vibro Compaction

Dynamic Compaction

Blast Densification

Compaction Grouting

Consolidation

PVD + Surcharge

Vacuum Consolidation

(Vibro Replacement)

Chemical Modification

Deep Soil Mixing

Jet Grouting

Injection Grouting

Reinforcement

Vibro Replacement

Geosynthetic Reinforcement

Rigid Inclusions

(Compaction Grouting)

Others

Removal & Replacement

Thermal

Electrical

Ground Improvement Methods

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PILES(bridge over weak soil)

REINFORCED GI TECHNIQUE(treat weak soil + strengthen with

stones, cement, etc.)

UNREINFORCED GI TECHNIQUE

(consolidation by weight)

Sett

lem

ent

0% 50% 100%

Soil Dependancy

Bridge over Poor Soil

100% 50% 0%

Ground Improvement: Soil Dependency

Deep Vibro Techniques

100

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Vibro Compaction

Vibro Replacement

Clay Silt Sand Gravel Stones Transition Zone

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Principle : Change in Density of Soil

Vibro Compaction

Vibro Compaction

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Schematic of Vibro Compaction

Ground Subsidence during Vibro Compaction

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GPS Antenna

Off-shore Vibro Compaction with Twin Vibro

Vibro Stone Columns – Concept

• Displacing the soil radially with the help of a depth vibrator, refilling with granular material and compacting

• Increases the density of the soil between the columns • Provides drainage • Increases stiffness of the soil

Before Treatment

After Treatment

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Depth Vibrator

Wet Top Feed Method

Dry Bottom Feed Method

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Dry Vibro Stone Columns – Execution

Very Soft to Med. Stiff Clay

Stiff to Very Stiff Clay Marine Deep Vibratory Replacement Columns

Vibrator String + Stone Feeder Pipe

GPS Antenna

Seabed

Offshore Installation (Bottom-Feed) Method

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Mechanical Cutting

Mechanical Mixing

Full Completed DSM Column

DSM Operation in field

Mechanical mixing of in-situ soils with a binder (e.g. cement, slag, lime, fly ash etc.) to improve shear strength and to reduce permeability of weak deposits.

Deep Soil Mixing

Very Soft Clay / Slime Cu = 5 to 10 kPa

Pile Like Element Cu = 100 to 2000 kPa

Deep Soil Mixing

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Installation of Deep Soil Mixing

Exposed Deep Soil Mixing Columns

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SoilfracTM Compensation Grouting:

Fracturing & Heaving of the soil with grout

TAM

SoilcreteTM Jet Grouting:

Eroding and mixing the soil with grout

Grouting:

Penetrating & filling soil voids with grout

TAM

Compaction Grouting:

Compaction/ Densification of soil with

stiff grout bulb

Introduction of liquid or dry binder (esp. cement material) into the weak soil mass, to improve its strength, stiffness and reduce permeability.

Grouting Techniques

Grouting techniques started from practice, not from theory”

Applications of Grouting

Reduction in Ground Water Seepage

• Rock Grouting

• Permeation Grouting

• Jet Grouting (Soilcrete)

Fissures / Cavity Treatment

• Rock Grouting

• Compaction Grouting

Soil Arching / Stabilisation

• Compaction Grouting

• Jet Grouting (Soilcrete)

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Grouted Layer

Rock Grouting

Permeation Grouting

Tube A Manchette (TAM) Technique – Grouted Body

Automatic Injection Containers – Computerised Grout Pumps

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Compaction Grouting

Jet Grouting (Soilcrete)

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• Suitability of Technique

• Are the encountered soil and suggested technique fundamentally compatible?

• Technical Compliance

• Does the suggested technique satisfy the design requirements ? (strength or stiffness?)

• Availability of Material

• Is the required material (stone, cement) readily available?

• Cost

• Is the proposed technique within the budget? What is the cost of time when there is saving?

• Protection of the Environment

• Does the suggested technique reduce or avoid pollution? Is the technique resource efficient?

Choice of Technique

Power Projects

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Thermal Power Plant, Punjab, India

• Compacted loose sandy layer up to 10m depth

• Achieved R.D >70% and liquefaction is addressed

• 1.2mio. m3 of Vibro Compaction

• Max. 0.7-1m settlement was observed out of 10m treatment (7-10%)

• Achieved Bearing Capacity is more than 20 T/m2

• Loose Sand with 6% fines from 2m to 10m below Existing Ground Level

• Load Intensities up to 15 T/m2 (lightly loaded structures)

• Bearing Capacity, Control of Settlements & Mitigation of Liquefaction

• Optimization of BCIS Piles (Axial & Lateral cap.)


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Mitigation of liquefaction potential & Improvement of bearing capacity of soil


Project :2 x 500MW Thermal Power Plant (Unit D)

Owner : Uttar Pradesh Rajya Vidyut Utpadan Nigam Ltd (UPRVUNL)

Location : Anpara, near Sonebhadra (U.P)

Structures : Coal Handling Plant

: Water System Package

: Substation (760 kV)

Construction Site : Abandoned Fly Ash Deposit resting on Clay Layer

Confirming Design : Deep Foundations to address Vertical & Lateral Loads

Power Plant Foundations on Fly Ash Deposit

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Soil Conditions (Typical)

Geotechnical Concerns

Bearing Capacity : < 10T/m2 (required > 10 T/m2) & excessive settlements

• Low lateral capacity : < 2 T for BCIS Piles (desired > 7T)

• Liquefaction : Zone III, Possibility of liquefaction

Geotechnical Value Addition:

• Combination of Ground Improvement & Bored Piles

• Ground Improvement using Vibro Stone Columns (dry bottom feed method) was suggested

• To enhance Bearing Capacity > 10T/m2 for Open Foundations

• To enhance Lateral Pile Capacity of bored piles to 7T

• To mitigate the Liquefaction potential

Foundation Solution

General Approach:

• Deep Foundations : for Settlement sensitive structures (ex. TG, Boiler, Stacker Reclaimer etc)

• Shallow Foundations : for Light to Medium loaded structures (ex. Pump House, Drive House, Cable Gallery, Sub-Station, water retaining structures etc, .

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• The deformations observed to be within allowable limits (5mm) at design load of 7T

• 0.5m dia. stone column grid was adopted for main works

Addressing Lateral Capacity of Piles

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0 5 10 15 20 25

Set

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Load in Tons

Lateral Pile Load Test Results

ITP-1

ITP-2

Installation of Stone Columns & Bored Piles

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Project Location : Maharashtra Wind Turbines : 25 (locations) for ground improvement Height : 65m Capacity : 850 kW Static Loads Self weight of turbine : 150 T Self weight of foundation: 300 T

Wind Mill Foundations- Maharashtra

Geotechnical Challenges

• Achieving required Bearing Capacity

• Satisfying ‘Rotational Stiffness’ requirements

• Working in high altitudes

Wind Mill Project, Maha

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838

840

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8580 10 20 30 40 50 60 70 80 90 100

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Standard Penetration Test, SPT N [ ]

GAL 14

Subsoil Data (Typical)

Typical Scheme & Activities

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Installed Wind Mills

Case Studies- Oil & Gas Sector

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LNG Tank Foundations

• Foundation for large diameter (84m) tanks (35m high) in seismic prone region

• Mitigation of liquefaction potential and limiting foundation settlements

LNG Tank Foundations

Hydrotest results are well with in permissible limits and operational since 2005

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HPCL Refinery, Ennore

• More than 30 Storage Tank Foundations

• Including Foundation for ancillary structures & Dykes

• Increase in bearing capacity and dyke stability & limiting foundation settlements

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Height

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igh

t (m

)

HPCL Refinery, Ennore

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Oil Storage Tanks, Gujarat

• More than 40 Storage Tank Foundations

• Foundation Solution for Tanks, ancillary structures & Buildings

Key Features

- Floating and Fixed Roof Tanks

- Tank Heights varying from 18 to 20m

- Diameter varying from 12m to 25m

Sub Soil Profile

Geotechnical Concerns :

- High Total & Differential Settlements

- Low Bearing Capacities

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Site Execution Pictures

Monitoring of Settlements

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Geotechnical Value Addition:

• Ground Improvement using Vibro Stone Columns was suggested the entire terminal

• Extensive soil investigation using eCPT’s and Boreholes

• Monitoring of tank settlements

• Resulted in savings of Cost & Time.

Completed Terminal

Case Studies- Industrial Plants

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Factories on Reclaimed Soil – Shipyard

Land reclamation

Fill thickness 5m to 30m

Qc about 4 to 6 MPa

RD about 30% to 40%

Factories on Reclaimed Soil – Structure

Hull shop Automated steel plate cutting and assembly 180m x 670m

50m tall

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• Foundation for columns • Foundation for floor slab


Automation => Sensitive to settlements

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Factories on Reclaimed Soil – Loading

Steel Plate Storage

Automated cutting and

forming

Automated assembly

Manual assembly

Finished product delivery

Settlements

Steel Storage Area < 100mm

Other Areas < 50mm

Differential ≈ 1 in 1000

Legend

Existing Boreholes (56 nos)

Existing CPT

Additional Boreholes

Additional CPT (> 60 nos. – more where you need them)

Collect Extensive Soil Information

Factories on Reclaimed Soil – Soil Investigation

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Factories on Reclaimed Soil – Soil Conditions

Loose reclaimed SAND

Stiff to very stiff clay

Soft to firm clay Hard clayey silt

Factories on Reclaimed Soil – Geotechnical Solution

Conforming : Driven Piles

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Factories on Reclaimed Soil – Site

Surcharge PVD rigs

VC cranes

Factories on Reclaimed Soil – Testing

Post CPT

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Factories on Reclaimed Soil – Shipyard

Vibro Compaction Rigs

PVD Rigs

• Physics (NSF) • Cost • Time • Materials & Carbon Footprint

Sewage Treatment Plant, NCR • Structures related to STP (Water retaining structures)

• Subsoil : Loose to medium dense fine Sand up to 10m

• Load intensities : up to 20 t/m2

• Concerns : Mitigation of Liquefaction Potential & Settlement Control

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• Concerns : Mitigation of Liquefaction Potential & Settlement Control

• Geotechnical Solution : Vibro Stone Columns ( Up to Liquefiable Depth ~10m)

• 1.5 to 3 Fold Increase in Post Qc and SPT Values.

Completed Structures

Industrial Plant

• Project : Chemical Plant

• Location : Kutch region, Gujarat State, India

• Structures: Industrial Structures

• Plot Area : 25 Ha.

• Main Structures:

• Sulphate of Potash (SOP) • Bromine Plant • Cogen Plant

• Other Structures:

• Storage Tanks • Workshops • Ware houses • Treatment Plants • Admin Buildings • Ancillary structures and other Amenities

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Soil Data

• Boreholes were explored to a depth of 20m to 25m below EGL and Uniform Soil Conditions through out the site

• Top 6m : Silty CLAY, SPT N is < 6

• 6m to 15m : Silty Sand with clay, N ≈ 40

• 15m to 25m : Hard Silty Clay, N > 50

• GWT was at 2m below EGL

Loading Conditions

• Foundation type : Piles for heavily loaded Structures : Raft for light to medium loaded Structures

• Loading Intensity : 100 kPa to 200 kPa

• Settlement criteria : < 100 mm (for shallow foundations)

Soil Data and Loading Conditions

Design Profile

Silty Clay

N < 6

Silty Sand with Clay

N = 40

Hard Silty Clay

Ave. N >60

BH Termination level

0.0

-6.0

-15.0

-25.0

Cost Effective Alternate Solutions

Pile Foundations Sulphate of Potash (SOP)

Bromine Plant Cogen Plant

Shallow Foundations on GI Storage tanks

Workshop Treatment Plant Ancillary structures and amenities Buildings and other storage areas

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Foundation Alternatives & Performance

• Heavily loaded structures were supported on 750mm dia. and 16m long BCIS Piles

• Lightly –medium loaded structures were rested on GI using Vibro Stone Columns (dry bottom feed method)

• Load Tests were conducted on Piles & GI and performance proved satisfactory.

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Load in Tons Routine Stone Column Load Test

Case Studies- Real Estate

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School Building, Noida (Vibro Compaction)

• Loose to medium dense fine Sand up to 9m with fines < 12%

• G + 3 School Building, required SBC is 20 t/m2 and N > 20

• Liquefaction Mitigation, Control of Settlements and Increasing Bearing Capacity,

• Vibro compaction up to 9m below EGL

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pth

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Pre SI BH2

Pre SI BH3

Perfrm. Line

Post SI BH4

Post SI BH5

School Building, Noida (Completed Structure)

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Tall buildings on GI, Haryana , India

Soil Data & Loading Conditions

Soil Data

•Boreholes were explored to a depth of 20m to 25m below EGL and Uniform Soil Conditions are found through out the site

•Top 7.5m : Silty SAND, SPT N varies from 6 to 17

•7.5m to 10.5m : Loose med. Sandy SILT, N ≈ 17 to 23

•10m to 20m : Med. Dense Sandy SILT, N > 40

•GWT was at 2m below EGL during investigation

Loading Conditions

• Foundation type : Raft

• Loading Intensity : 150 kPa

• Settlement criteria : < 75 mm

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Bearing Capacity & Liquefaction

Main Technical Concerns are………………

• Low Bearing Capacity due to weak soil

• Total & Differential Settlements

• Mitigating Liquefaction (Zone 4, 0.24g)

Required Geotechnical Solution………

Reinforcement To improve composite shear strength

Compaction in granular/soft subsoil To increase composite compression modulus

Large Drainage path To improve overall permeability

Mitigate Liquefaction

Site View (during execution)

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Group Load Test & Performance

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Set

tlem

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Load in 'Tons' Load vs Settlement

Load Intensity Settlement @ Design Load

Net Settlement

All. Settlement as per IS 15284 (Part 1): 2003

150 kPa 10.2 mm 6.7 mm 30 mm

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Time in Weeks

F1 F2 F3 F4 Floor Level


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Site Pictures - Present Status

G+14 Storied Towers

Housing on GI – Resedential Building, Chennai

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Project Background

• Project : INFINITY, Porur

• Location : Porur Gardens, Chennai

• Building : Stilt + 4 floors

• Total flats: 198 units

• Raft Area : 5600 sq.m

• Plot Area : 2.5 Acres (~100m x 100m)

Soil Data

• 4 Boreholes were explored to a depth of 20m to 25m below EGL and Uniform Soil Conditions through out the site

• Top 6m : Silty sandy CLAY with 20 to 40% fines

• Below 6m : Medium dense SAND up to 12m, followed firm to stiff silty CLAY up to explored depth

• GWT was at 3m below EGL during investigation (Sep 2012)

Loading Conditions

• Foundation type : Raft

• Loading Intensity : 100 kPa

• Settlement criteria : < 100 mm

Soil Data and Loading Conditions

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Vibro Stone Columns with Dry Bottom Feed Technique

• Treatment depth = 6 to 8m below EGL

• Area replacement = 18% to 22%

Proposed Ground Improvement Scheme

Advantages to the Investor:

• Savings in Time for about 6 months • Reduced Carbon footprint • Locally available stone material (avoided usage of large quantity of cement and steel) • Early Completion of Project (benefit to Investor by Saving site OH + benefit to Banker by

early disbursement of Loans => Early completion and delivered to End User)

• To check post treatment performance of ground

• Established 14 settlement monitoring points

• Regular monitoring of vertical movement of raft foundation


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0 4 8 12 16 20 24 28 32 36 40 44 48 52 56 60 64 68 72 76 80 84 88 92 96 100 104 108

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ture

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a)

Settlement Results - All Pours

Load vs Time Curve

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Time in Weeks

Point: P1S1 Point: P1S2



Predicted settlement

Settlement vs Time Curve

Completed Structure

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Case Studies- Transportation

Compaction Grouting -SMART Project, Malaysia

Soil stabilization and cavity filling

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North Drive South Drive

SMART Project, Malaysia

Rock Grouting- SMART Project, Malaysia

Dry walls after curtain grouting

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Compaction Grouting - DMRC Saket, India

Soil arching – NATM construction

GI for Roads and High Speed Railways

13m High RE Wall

Double Track Project, Malaysia

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• Automated Real Time Monitoring of Installation Process • Reliable investigation techniques (Electric Cone Penetration Testing, SPT’s etc) • Post improvement testing by Load Tests • Good quality of Back Fill Material

Quality Control Measures – Pre and Post

eCPT’

Figure 7 Keller’s Automatic

Quality Control System(M3 / M4 Computer)

Figure 7 Keller’s Automatic

Quality Control System(M3 / M4 Computer)

Automated Real Time Quality Control

Concluding Remarks

Ground improvement techniques such as Vibro Compaction, Vibro Stone Columns, Deep Soil Mixing, Jet Grouting can be used to provide Optimal Foundations.

These techniques can be used both for heavy, tall & settlement sensitive structures and also for smaller simpler structures

Opting for Optimal foundation solution offer savings in cost, time, materials, convenience and protection to the environment

Excellent soil information, a correct choice of technique, good equipment, experienced people, testing and monitoring during and after construction is essential for successful project completion.

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Thank you for your attention………

[email protected]

Key Factor: Reliable Soil Investigation…..!!!!!

• Reliable soil data is must to OPTIMIZE appropriate foundation alternatives

• Advanced investigation techniques such as eCPTs shall be adopted to obtain relevant soil data over the project area along with few confirmatory BHs

optimal foundations - iit gandhinagar foundations... · • more than 40 storage tank foundations...

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