understanding of foundations: success of a civil … · understanding of foundations: success of a...

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Understanding of Foundations:

Success of a Civil Engineer….!

Part B: Heavy Foundations

• Theory: Behaviour of Pile Foundations

• Design of Pile Foundations

• Case Study 1 : Heavy Foundations for Power Plant

• Case Study 2 : Deep Excavation Pit

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Behavior of Pile Foundations

Pile Foundations – Load Transfer Mechanism

Initially Pile-Soil system behaves elastically

Mob. of Friction: 0.3% to 1% of dia.

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Pile Foundations – Load Transfer Mechanism

Mob. of Friction: 0.3% to 1% of dia.

Pile Foundations – Failure Mechanism

4

P M

V

Pile cap

Batter pile

Vertical pile

Axially Loaded Piles

P P M

V

Axially Loaded Piles – Load Transfer

W

5

M

z

Deflection

y

Slope

S

Moment

M

Shear

V

Soil Reaction

p

Forces and Deflections of Long Piles

Method of estimation of Pile Capacity

By the use of static bearing capacity equations

By the use of the values of SPT and CPT

By field load tests

By dynamic method

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Ultimate Pile Capacity (IS 2911)

Ultimate Capacity of Pile , Qult = QEB + QSKIN – Wp

QEB = Ultimate End Bearing

QEB = c* Nc + Pd * Nq * Ap

QSKIN = Ultimate Skin Friction

QSKIN = *c + K*P*tan x As

Wp = Self weight of Pile

Qsafe = Qult / FoS

Qult

QEB

QSKIN

Ultimate Capacity of Piles - Self Weight

Ultimate Capacity of Pile , Qult = QEB + QSKIN – Wp

Ultimate End Bearing, QEB = 300 T FoS = 2.5

Ultimate Skin Friction, QSKIN = 100 T

Self Weight of Pile, W = 20 T

Case 1: Qsafe = Qult / FoS = 160 T (EPC Contractors)

Case 2: Qsafe = (Qult – W) / FoS = 152 T (Reasonable)

Case 3: Qsafe = Qult / FoS – W = 140 T (Consultants)

(too conservative, consultants may prefer…….or Contractors of item rate

contracts)

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Pile Foundations – Uplift Capacity of Pile

Quplift

QSKIN

W

Uplift Capacity of Piles

Ultimate Skin Resistance,

QSKIN = *c + K*Pdi*tan x As + Wp

For Cohesive Soils:

The skin resistance in both compression and uplift cases

are same

For Cohesionless Soils

A reduction of 50% to 33% is generally adopted (industry practice)

Ultimate Uplift Capacity = 1/2 to 2/3 of Ultimate Skin

Resistance.

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Negative Drag on Piles

Factor of Safety = Ult. Skin Resistance of Single Pile

Working load + (-) ve skin friction


• Behaviour of Pile Foundations



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Artistic View of Thermal Power Plant

2 X 660 MW (Phase 1)

Soil Profile & Operational Challenges

-70

-60

-50

-40

-30

-20

-10

0

0 10 20 30 40 50 60 70 80 90 100

Ele

va

tio

n [

m]

Standard Penetration Test, SPT N [ ]

GWT

40m

60m

10

Casing

Drilling fluid enables for the application of

hydrostatic pressure against the sides of

the pile by creating a bridging effect :

If top level of Drilling Fluid drop below ground

water table, the pile hole will collapse.

When Pile Bore Collapse happen.....?

Water Table

Casing

Stable Pile Bore Un-stable Pile Bore

Water Table

Operational Excellence with “Best Practices”

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Quality – Borehole Stability

Top Vibro Hammer to install 10m deep Temporary Casing

Quality – Bentonite Recycling

De-sanders to ensure quality of recycled Bentonite for borehole stability

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Pile Integrity Tests for all Installed Piles to ensure Quality of Piles

Quality – Testing (PIT)

Load Test Setup for 1200MT

Quality – Testing (PLT)

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Productivity – Timely Concreting

Timely Concreting (Dedicated Batching Plant ~ 1,00,000m3 batched on site)

Productivity – Supporting Equipment

Dedicated Equipment to ensure optimal cycle times of piling process

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Note: Above piles installed to 40m depth using 3 rigs (avg. productivity ~ 50 nos x 40m / 3 rigs / 6 days ~ 111 lin.m. / rig / day)

30

50

70

90

110

130

150

170

Au

g-1

1

Au

g-1

1

Sep

-11

Oct

-11

No

v-1

1

Dec

-11

Jan

-12

Feb

-12

Mar

-12

Ap

r-1

2

May

-12

Jun

-12

Jul-

12

Jul-

12

Rat

e o

f P

rod

uct

ion

(Li

n.m

/Rig

/Day

)

Week

Weekly Rate of Production

Productivity


• Behaviour of Pile Foundations



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Past Experience

BBCL – Breeze Residences, Chennai

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About the project

• Project : 3B+G+18 storeyed Residential Project

• “Breeze Residences”, Kilpauk, Chennai

• Developer : M/s BBCL Developers Pvt Limited.

• Client Consultant : M/s. Buro Engineers Ltd.

• Specialised Foundation: M/s. Keller Ground Engineering India Pvt. Ltd.

Contractor

• Keller scope : Design & Build contract - BCIS Pile foundation &

Permanent Retention System

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Project Location

32 32 32

Plan Layout

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33 33 33

Geotechnical Challenges

• Loose/weak layers at top (N~5) - Low in-situ bearing pressure

• Hard strata at deeper depths - Foundation piles to be designed as

end bearing & shall rest on rocky strata

• Deeper Excavation(-10.2m) - Overall stability is a concern

• Sandy soils (Fines~5% to 25%) - Exerts high Lateral pressure on wall

& Shallow GWT(-5.0m from EGL)

• Continuous Dewatering reqd. - Chances of seeping of soil particles

• High lateral wall deflection - Ground subsidence

• Settlements & Tilting of adjacent buildings

34 34 34

Scope of Work - Foundation Piles

Foundation Package

Design & Build Depth Optimization

BCIS Piles 900, 750 & 600mm Piles (186 Nos.)

Pile Load Tests Routine Tests (3 Nos.-1 for each dia.)

PIT 107 Nos

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35 35 35

Scope of Work – Retention System

Retention Package

Design & Build Contiguous Bored Pile with Inclined Anchors

BCIS Piles

Retention (145 Piles)

Retention Cum Foundation (57 Piles)

Grouting Cement : Bentonite (201 Nos.)

Anchors 1st level – 103 Nos

Capping Beam Length – 172m

36 36 36

Design of Foundation Piles

Confirming Design by M/s BBCL (Client)

Proposed by M/s Keller (Depth Optimization)

SI. No. Pile dia.

(mm)

Length of pile

(m)

Vertical Pile capacity

(MT)

1 600 15 150

2 750 15 230

3 900 15 300

SI. No. Pile dia (mm) Length of pile

(m)

Vertical Pile capacity

(MT)

1 600 12.5 175

2 750 13.0 260

3 900 13.0 332

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37 37 37

Layout Plan – Foundation Piles & Retention System

38 38 38

Preliminary Analysis – GGU Retain

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39 39 39

Proof Checking – Plaxis 2D

40 40 40

Summary of Results

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41 41 41

Typical Cross Section

42 42 42

Execution – Installation of Piles

Casing installation

Boring in

progress

Flushing

Concreting

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43 43 43

Execution – Vertical Grout Columns

Inclination checking Boring in progress Grout mixer set-up

Primary Grouting Secondary Grouting

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Execution – Ground Anchors

Inclination checking Anchor Fabrication

Anchor Installation Anchor Strand Spacer Grout Pipes

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45 45 45

Execution – Capping Beam

Levelling & Preparation Laying of PCC

Reinforcement fabrication Completed Capping Beam

46 46 46

Deflection Monitoring Points

Deflection monitoring points

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47 47 47

Deflection Monitoring Results

Maximum Predicted Deflection = 39 mm

(Plaxis Analysis)

Recorded settlement = 9mm

48 48 48

Completed Picture

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Completed Excavation

Completed Excavation

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Present site condition

Basements completed

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Latest Photograph

Past Experience

VGN – Notting Hill, Nungambakkam, Chennai

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About the project

• Project : Residential Building (3B+G+16 Floors)

• Developer : M/s VGN Developers Pvt. Ltd.

• Total Basement Area : 2175.7 sq.m

• Site dimensions : 60mx36m

• Excavated Perimeter : 218m (approx.)

• No. of Basements : 3 Nos.

• Depth of excavation : 8.5m from present ground level (RL -3.0m)

• Working level : 3.0m below NGL (RL 0.0m)

• Retention system : Contiguous Bored Pile wall with 1 level anchor

• Structure : Multi-storeyed (G+16) Residential buildings with 3 basements

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Project Location

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57 57 57

Plan Layout

Ad

jacen

t B

uild

ing

(G+

5)

(W

est

sid

e)

Adjacent Building (G+7) (South

side)

58 58 58

Subsoil Condition

Typical Soil Profile

0.0

14.0

17.0

Dense Silty

Sand+Gravel

N>50, φ= 36°

Weathered Rock

N>100,

Cu=400kPa

2.0

MD Silty Sand

N~17, φ= 30°

Clayey Sand /

Sandy Clay

N~8, Cu=40kPa

Filled up

N~7, φ= 28°

10.0

20.0

6.0

MD to Dense

Silty Sand

N~30, φ= 34°

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59 59 59

Geotechnical Challenges

Following are the challenges related to RETENTION SYSTEM FOR

DEEP EXCAVATION may need to be addressed:

• Deep Excavation (depth ~ 11.5m) adjacent to tall structures (G+7)

• Overall Stability of the excavation system

• Nature of in-situ soil – Granular content (70% to 90%) which exerts

high lateral pressure than cohesive soil

• Ground Water Level at Shallow Depth (3m below EGL)

• Settlement/ tilting of existing structures adjacent to the excavation

• Ground Subsidence due to excessive dewatering (retention side)

• Lateral deflection of the Retention

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• CB piles

• Number of piles - 271nos

• Diameter of piles - 750mm with 820mm c/c distance

• Length of retention piles - 16m from Present ground level

• Grout columns

• Number of Grout columns - 270 nos. with 12m depth from Present GL

• Diameter of grout columns - 150mm

Proposed retention system - CBP wall with inclined anchors

Pre excavation of about 3m were carried out at site to optimize the design of retention system

Total length of retention - 218m

Detail showing Retention piles with Grout columns


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•Inclined anchors

• Number of Inclined anchors - 130 nos at 1.64m c/c

• Capacity of anchors - 50T

• Anchor level - 5.0m below NGL

• Fixed length of anchors -11m

• Free length of anchors - 8m

•Anchor inclination - 50o

Typical Cross section of Inclined Anchor

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• Waler beam

• Total length of waler beam - 218m

• Steel Waler beam - ISMC 400 (2 nos.) connected back to back

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Retention System Layout – Initial Proposal


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Retention System Layout – Existing Old

Foundation Piles

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65

Realignment of Retention System


66 66 66

Preliminary Analysis – GGU Retain

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67 67 67

Proof Checking – Plaxis 2D

68 68 68

Summary of Results

GGU Analysis Plaxis Analysis

GWT at -6.0m GWT at -6.0m

Plie dia., m 0.75 0.75

Pile spacing, m 0.82 0.82

Pile length, m 16 16

Embedment, m 7.5 7.5

Surcharge, kPa 10 20

GWT @ Retention side, m -6.0 -6.0

Max BM, kN.m/m Wall 409.3 484

Max SF, kN/m Wall 248.39 214

Anchor Capacity, Tons 50 50

Deflection, mm 1 in 550 1 in 400

DescriptionGWT at -2.5m GWT at -2.5m

Pile dia., m 0.75 0.75

Pile spacing, m 0.85 0.85

Pile length, m 16 16

Embedment, m 8.6 8.6

Surcharge, kPa 10 20

GWT at retention side, m -2.5 -2.5

Max BM, kN.m / m wall 468 562

Max SF, kN / m wall 249 193

Anchor force, Ton / m wall 24 27

Anchor Capacity, Tons 41.0 46.0

Deflection, mm 1 in 500 (15mm) 1 in 250 (30mm)

No. of models (options) 20 to 25 6 to 8

DescriptionGGU Analysis Plaxis Analysis

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69 69 69

Typical Cross Section

70 70 70


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71 71 71


Maximum Predicted Deflection = 25 mm

(Plaxis Analysis)

Recorded settlement (till date) = 17 mm

-10

-9

-8

-7

-6

-5

-4

-3

-2

-1

0

1

2

3

4

5

6

7

8

9

10

11

0 5 10 15 20 25 30

Plaxis 3 4

5 6 7

8 9 10

11 12 13

14 15 16

17 18

72 72 72

Completed Picture

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73 73

Introduction to Diaphragm Wall system

74 74

What is Diaphragm Wall?

A Diaphragm wall is a technique used to build

reinforced concrete walls in the area of soft earth

close to open water or with high ground water table

to stabilize deep excavations and as deep

foundation elements.

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75 75

About Diaphragm Wall • Diaphragm walls are typically constructed by starting

with a set of guide walls, typically 1 meter deep and 0.5

meter thick.

• The guide walls are constructed on the ground surface

to outline the desired slurry trench(es) and guide

excavation.

• Excavation is done using a special clamshell-shaped

digger or a hydromill trench cutter. The excavator digs

down to design depth, or bedrock, for the first cut.

• The excavator is then lifted and moved along the trench

guide walls to continue the trench with successive cuts

as needed.

• The trench is kept filled with slurry (usually a mixture of

bentonite and water) at all times to prevent collapse.

76 76

About Diaphragm Wall • Once a particular length is reached, a reinforcing cage is

lowered into the slurry-filled pit and the pit is filled with concrete

from the bottom up using tremie pipes.

• The concrete displaces the bentonite slurry, which is pumped

out and recycled.

• Slurry walls are built to enclose the desired area, blocking water

and softened earth from flowing into it.

• On completion of concreting, digging within the now concrete

wall-enclosed area can proceed.

• To prevent the concrete wall from collapsing into the newly open

area, temporary supports such as tiebacks or anchors are

installed.

• When completed, the structure built within the walled-off area

supports the wall, so that tiebacks and/or other temporary

bracing may be removed.

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77 77

Construction Procedure of Diaphragm Wall

Construction Procedure of D-wall

78 78

Construction Procedure of Diaphragm Wall (Typical)

Stage 1: Construction of Guide Walls

Stage 2: Preparation of the Supporting Slurry

Stage 3: Excavation of Diaphragm-wall

Stage 3a: Stop Ends Fixing

Stage 4: Lowering of Reinforcement Cage

Stage 5: Concreting & Stop Ends Removal

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79 79

Project Background

80 80

Project Background

• Project : Commerzone IT Building (3B+G+9F)

• Location : Porur, Chennai

• Owner : M/s K Raheja Corp

• Total Plot Area : 25,800 Sq. M (approx.)

• Total Basement Area : 15,250 Sq. M (approx.)

• Excavated Perimeter : 650 m (approx.)

• No. of Basements : 3 Nos.

• Retention system : Diaphragm wall with Anchors

• Depth of excavation : 11.3m from Existing Ground Level (EGL)

• Scope of Work : Design & Execution of Diaphragm Wall.

• Area of D-Wall : 11, 700 Sq.M

• Depth of Retention : ~18m

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81 81

Aerial View

82 82

Overall Layout Plan

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83 83

SPT N value & Grain Size Distribution

84 84

Idealised Soil Profile

Soil Description Depth

from

(m)

Layer

thk. (m)

SPT N

Values

Clayey silt (MI) / Silty Clay (CI) 0.0 3.0 11

Clayey silt (MH) / Silty Clay (CH) 3.0 3.0 14




Clayey Silty Sand (SM) / (SC) 13.0 2.0 6

Clayey Silty Sand (SM) / (SC) 15.0 3.0 50

Weathered Rock 18.0 6.0 >100

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85 85

Geo-Technical Problems

The geotechnical problems of the site are listed below,

• Proposed site comprises of top 15m compressible silty clay.

• High Ground water table (GWT at 2.5 m below EGL).

• Adjacent building with closer setback distances (say 9m).

• Deep excavation (11.3m below EGL).

• Overall stability of Retention system.

86 86

Design Considerations

Retention System Details:

• Length of Retention system : 650 m

• Existing Ground Level : 0.0 m

• Final Depth of Excavation : 11.3 m below EGL

• Design Water Table : 2.5 m below EGL

Possible solutions:

• Contiguous bored pile (CBP) wall with lateral support

• Diaphragm wall with lateral supports - SELECTED

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87 87

Retention System used for analysis

-12.3 m GWT

88 88

Typical D-wall Cross Section

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89 89

Wallap Analysis (Stretch-1)

90 90

Wallap Analysis Results (Stretch-1)

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91 91

Wallap Analysis (Stretch-2)

92 92

Wallap Analysis Results (Stretch-2)

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93 93

Plaxis Analysis (Stretch-1)

94 94

Plaxis Analysis Results (Stretch-1)

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95 95

Plaxis Analysis Results Summary (Stretch-1)

96 96

Plaxis Analysis (Stretch-2)

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97 97

Plaxis Analysis Results (Stretch-2)

98 98

Plaxis Analysis Results Summary (Stretch-2)

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Project Information

• Project : Construction of Diaphragm wall for Underground Metro

Station, Hazratganj

• Location : Hazratganj, Lucknow

• Owner : Lucknow Metro Rail Corporation (LMRC)

• Main Con : M/s Gulermak - Tata Projects Limited JV

• Design consultants : Tandon Consultants – Geoconsultants JV

• Structure : Station Box with 2 level basement

• Total perimeter : 860m

• Depth of D-wall : 21.5m from EGL

• Total D-wall area : 18,500 sq.m

• No. of panels : 168 nos. (5m each)

• Total excavation depth : ~17.5m below EGL

100 100 100

Project Location

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101 101 101

Plan Layout

D wall Thickness : 800 mm & 1000 mm

Length of D wall : 840 m

No. of panels : 168 Nos.

Depth of D wall : 21.5 m below EGL

Final depth of excavation : 17.5 m below EGL

102 102 102

Cross Section Layout

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103 103 103

Subsoil Condition

Depth

From (m)

Depth

to (m)

Layer

Thick (m) Soil Description SPT N Range

0.0 7.0 7.0 Silty Sand (SM) 10-20

7.0 24.0 17.0 Sandy Clayey Silt (ML/CI) 20-40

24.0 30.0 6.0 Silty Sand (SM) 40-60

104 104 104

Execution - Overall Site View

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105 105 105

Execution – Grabbing

Grabbing

106 106 106

Execution – Cage Lowering

Reinforcement Cage Erection

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107 107 107

Execution – Concreting & Stop end removal

Concreting Stop end removal

108 108 108

Execution – Roof slab construction

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109 109 109

Execution – Excavated Portion

110 110 110

Quality Checks for Polymer

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111 111 111

Quality Checks – Koden Results

• Ground Improvement Techniques such as Deep Vibro Techniques can

be used to provide Optimal Solutions

• Design & Build expertise will ensure savings in Cost & Time

• Execution of Specialized Foundation Techniques requires state-of-the-

art experience with Operational Excellence and Best Practices

• Execution of Deep BCIS Piles requires state-of-the-art process

• International standard of practices using latest equipment ensures the

success of a project

• Safety goal of zero accidents is possible with dedicated safety systems

and motivated leadership

Conclusions

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Independent Foundation Package

• Allows for specialist foundation works with defined specifications

• Quality works will be delivered in a timely manner

• Combination of heavy foundations (bored piles) and open foundation (ground improvement techniques) for overall cost optimization

• Organisations following the above • HPCL • BPCL • MRPL • IOCL • BHEL

Keller’s Ideal Worker (Kelwin)

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All the best & Good Luck…..!

Thank you for your kind attention…….!

What Keller do…….?

BCIS Piles

Soil Anchors

DSM

Micro Piles

Grouting

Tank Foundations Stone Columns

Driven Piles

understanding of foundations: success of a civil … · understanding of foundations: success of a...

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