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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
80
60
40
20
0
100
80
60
40
20
0 0,6 0,002 0,006 0,02 0,06 6,0 20 60 0,2 2,0
Grain Size [mm]
Per
cen
tag
e P
assi
ng
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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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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• 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.)
Thermal Power Plant, Punjab, India
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Mitigation of liquefaction potential & Improvement of bearing capacity of soil
Thermal Power Plant, Punjab, India
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
0
2
4
6
8
10
12
14
16
18
20
0 5 10 15 20 25
Set
tlem
ent,
mm
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
842
844
846
848
850
852
854
856
8580 10 20 30 40 50 60 70 80 90 100
Ele
vati
on
[m
]
Standard Penetration Test, SPT N [ ]
GAL 14
Subsoil Data (Typical)
Typical Scheme & Activities
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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
-300
-270
-240
-210
-180
-150
-120
-90
-60
-30
0
30
1-M
ar-1
1
11
-Mar
-11
21
-Mar
-11
31
-Mar
-11
10
-Ap
r-1
1
20
-Ap
r-1
1
30
-Ap
r-1
1
10
-May
-11
20
-May
-11
30
-May
-11
9-J
un
-11
19
-Ju
n-1
1
29
-Ju
n-1
1
Sett
lem
en
t [m
m]
Days
Pt2
Pt3
Pt4
Pt5
Pt6
Pt7
Pt8
Pt9
Pt10
Pt11
Pt12
Pt13
Pt14
Pt15
Pt16
Pt17
Pt18
Pt19
Pt20
Height
He
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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0
4
8
12
16
20
0 50 100 150 200 250 300
Sett
lem
ent i
n m
m
Load in Tons
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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Factories on Reclaimed Soil – Structure
• Foundation for columns • Foundation for floor slab
Factories on Reclaimed Soil – Structure
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.
0
5
10
15
20
0 25 50 75 100
Set
tlem
ent,
mm
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
0
1
2
3
4
5
6
7
8
9
10
0 10 20 30 40 50 60
De
pth
[m
]
SPT N [ ]
Pre SI BH1
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
0
5
10
15
20
25
30
35
40
0 100 200 300 400
Set
tlem
ent
in 'm
m'
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
-20
-18
-16
-14
-12
-10
-8
-6
-4
-2
0
2
4
6
8
10
12
14
16
18
20 -100
-90
-80
-70
-60
-50
-40
-30
-20
-10
0
10
20
30
40
50
60
70
80
90
100
0 6 12 18 24 30 36 42 48 54 60 66 72 78 84 90 96 102
Flo
or
Lev
el
Set
tlem
ent
'mm
'
Time in Weeks
F1 F2 F3 F4 Floor Level
Monitoring of Settlements
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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
Monitoring of Settlements
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Monitoring of Settlements
0
10
20
30
40
50
60
70
80
90
100
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
Sup
er s
truc
ture
load
(kP
a)
Settlement Results - All Pours
Load vs Time Curve
0
10
20
30
40
50
60
70
800 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
Set
tlem
ent
'mm
'
Time in Weeks
Point: P1S1 Point: P1S2
Point: P3S2 Point: P4S1
Point: P4S3 Point: P6S3
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………
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