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Piling In Difficult Ground ConditionsDr.K.S.Rama Krishna Larsen & Toubro Ltd ECC-Division Chennai

Difficult Ground Conditions for Piling1.Piling in Soft Soils Over Rock 2.Piling in Bouldary Soils 3.Piling with Socketing in Rock 4.Piling on Slopes 5.Piling in Soils with Under water Streams 6.Piling Through Loose Fills under High Water Table 7.Piling Over Water

Piling with Socketing in Rock27-11-2010 L&T-ECC Division : Dr.K.S.Rama Krishna : Piling in Difficult Ground, IGS, Madurai 2

Piling With Socketing in Rock1.Bored Cast-In-Situ Piles with Socketing in Rock 2.Precast Concrete/Steel Piles with Socketing in Rock

Bored Cast-In-Situ Piles with Socketing in Rock

27-11-2010

L&T-ECC Division : Dr.K.S.Rama Krishna : Piling in Difficult Ground, IGS, Madurai

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Bored Cast-In-Situ Piles with Socketing in RockContents:A. Our Current Projects B. Some Design Aspects C. Construction Practices D. Importance of Equipment & Tools E. A Process Approach Being Followed In L&T Sites F . Use of Polymer as Drilling Mud G. Suggested Process for a Sound Rock Socket27-11-2010 L&T-ECC Division : Dr.K.S.Rama Krishna : Piling in Difficult Ground, IGS, Madurai 4

A. Current Infrastructure Projects of L&T with Bored Piles Socketed in Rock

27-11-2010

L&T-ECC Division : Dr.K.S.Rama Krishna : Piling in Difficult Ground, IGS, Madurai

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Bored Piles Socketed in Rock -:L&T Projects:Project1. 2. 3. 4. 5. 6. MIAL, Mumbai Mono Rail, Mumbai Nasik Elevated Corridor Bangalore Metro Rail Project Chennai Metro Rail Project Hyderabad Metro Rail Project

Type of Rock- Basalt, Breccia, Trachyte - Basalt, Breccia, Trachyte - Breccia, Basalt - Granite, Gneiss, Schist - Charnockite - Laterites, Basalts

27-11-2010

L&T-ECC Division : Dr.K.S.Rama Krishna : Piling in Difficult Ground, IGS, Madurai

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Pile Sizes and CapacitiesProject MIAL(Mumbai International Air port) MONO RAIL, Mumbai Nasik Elevated corridor Bangalore Metro Rail Project Chennai Metro Rail Project Hyderabad Metro Rail Project Pile Diameter (mm) 600,800,1000 800,1000 1000 1200 1200 No of piles 5000 3000 500 900 500 Compression Capacity(MT) 140,250,400,500 T 350,500 T 500 T 500T 500T

Design Stage Monopile Under Consideration

27-11-2010

L&T-ECC Division : Dr.K.S.Rama Krishna : Piling in Difficult Ground, IGS, Madurai

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B. Some Design Aspects for Rock Socketed Bored Piles

27-11-2010

L&T-ECC Division : Dr.K.S.Rama Krishna : Piling in Difficult Ground, IGS, Madurai

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Rock Socket Friction

is a function of

Surface Roughness of Rock Socket Unconfined Compressive Strength of Intact Rock

Confining Stiffness Around the Socket in Relation to Fractures of Rock Mass &

Socket DiameterSocket Length-to-Diameter RatioL&T-ECC Division : Dr.K.S.Rama Krishna : Piling in Difficult Ground, IGS, Madurai 9

27-11-2010

Cole & Stroud MethodIS 2911, Part-1, Section 2

In Hard Rock 300mm Penetration for Large Diameter Piles In Weathred or Soft Rocks: 1) Shear Strength of Rock based on Rock Type & Quality ( Easy methods of Identification in Field) 2) Standard Pile Capacity Estimate using inputs from Point 1 and arrive capacity/Socket Length27-11-2010 L&T-ECC Division : Dr.K.S.Rama Krishna : Piling in Difficult Ground, IGS, Madurai 10

Cole & Stroud Chart for Piles socketted in Weak rocks Basis for Draft IS2911 Part I Sec 227-11-2010

L&T-ECC Division : Dr.K.S.Rama Krishna : Piling in Difficult Ground, IGS, Madurai

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Cole & Stroud Table for Piles socketed in Weak rocks (Ref: Draft IS-2911 Part I Sec 2)

27-11-2010

L&T-ECC Division : Dr.K.S.Rama Krishna : Piling in Difficult Ground, IGS, Madurai

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IRC SPECIFICATIONSMethod -1: Where Rock Cores can be taken & UCS Established

Qu = Ksp x qc x df x Ab + As x Cusqc = average UCS of rock Ksp = An empherical coefficient whose valueranges from 0.3 to 1.2 for the rocks where core recovery is reported.

Cus = Ultimate shear strength along socket length = 0.225(qc), The same shall be restricted to 5Mpa

(CR+RQD)/230% 100%

Ksp0.3 1.2

CR : Core Recovery ; RQD : Rock Quality Designation27-11-2010 L&T-ECC Division : Dr.K.S.Rama Krishna : Piling in Difficult Ground, IGS, Madurai 13

Pile capacity chart Based on IRC78:2000-Cole and Stroud Method 2: When RQD shows Highly Fragmented StrataStrength/ Consistency (qc) Approx N Value Compressive Strength in Mpa Strong Moderately Moderately Weak Strong Weak > 600 80-40 600-400 40-10 400-200 10-4 200100 4-1.4 Very Weak 100-60 1.4-0.8

Qu = Re+Raf = Cu.b x Nc x Ab + Cus x As Where, Cub = Average shear Strength below base of pile for the depth twice the diameter/ least lateral dimension of pile. Cus = Ultimate shear strength along socket length = 0.225(qc), The same shall be restricted to 5Mpa L = Length of socket Nc = 9 Factor of safety : Skin friction = 10 and End bearing = 527-11-2010 L&T-ECC Division : Dr.K.S.Rama Krishna : Piling in Difficult Ground, IGS, Madurai 14

IRC SPECIFICATIONS Large Diameter Bored piles : Pile Dia > 600mm Design : Safe load capacity = Socket friction+ End Bearing Minimum socket length: Hard rock = 300mm Weathered Rock = 0.5x Dia of pile Ignore top 300mm socket length for calculation of socket friction capacity. Friction Capacity Shall be limited to 6 times Diameter of piles The allowable end bearing component after dividing by factor of safety shall be restricted to 5Mpa. Minimum Grade of concrete : M35 Factor of safety on Friction component : 10 Factor of safety on End Bearing Component : 5 Minimum Diameter of Pile:Bridges on land :1000mm River Bridges : 1200mmL&T-ECC Division : Dr.K.S.Rama Krishna : Piling in Difficult Ground, IGS, Madurai

27-11-2010

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Hong Kong Specifications Large Diameter Bored Piles(LDBP) : Pile Dia>600mm Design: Granitic & Volcanic Bed RocksSafe Load Capacity = Socket Friction + End Bearing Socket Length Min (2 x Pile Dia Or 6m) Ignore top 600mm socket length For LDBP : Minimum Grade of Rock = Gr. III Allowable Socket Friction: Min Gr.II + TCR 95% + UCS 50MPa = 700 kPa Min Gr.III+ TCR 85% + UCS 25MPa = 500 kPa Concrete Min 30MPa In Case Gr. II & Gr. III met in Pile Bore USE Gr.III for Socket Friction

Soil Investigation : At Every Pile Point:BH = 1 For Pile Dia < 2.5m & 2 for Pile Dia >2.5m Continuous Rock Core(N-Size) for Length = 600mm+1.5 Pile Dia below Bed Rock LevelL&T-ECC Division : Dr.K.S.Rama Krishna : Piling in Difficult Ground, IGS, Madurai 16

27-11-2010

Hongkong- Stringent Quality Standard for Piling

100% predrilling prior to pile drilling 100% verticality check, 10% verticality check by Kodenor as per Specifications

100% Sonic Logging 100% Interface Full core of pile 5% to 10% depending onSpecifications

Material testing such as cube crushing and RebarTensile Test as per Specifications27-11-2010 L&T-ECC Division : Dr.K.S.Rama Krishna : Piling in Difficult Ground, IGS, Madurai 17

From Tomlinson

27-11-2010

L&T-ECC Division : Dr.K.S.Rama Krishna : Piling in Difficult Ground, IGS, Madurai

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C. Construction Practices

27-11-2010

L&T-ECC Division : Dr.K.S.Rama Krishna : Piling in Difficult Ground, IGS, Madurai

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Design & Construction Compatibility1. Design of Bored Piles in general & Rock Sockets in Particular MUST Consider Construction Practices 2. Equipment, Tools & Methods Play an Important Role in Quality, Time and Cost

3. Construction Process(QA/QC) Determines the Capacity27-11-2010 L&T-ECC Division : Dr.K.S.Rama Krishna : Piling in Difficult Ground, IGS, Madurai 20

Tripod, Bailer & Chisel MethodConventional Tripod System BAILER

Productivity : No.of days per pile, Depends on Many factors27-11-2010 L&T-ECC Division : Dr.K.S.Rama Krishna : Piling in Difficult Ground, IGS, Madurai

3.5 T CHISEL21

Limitations of Tripod- Chisel- Bailer Method1. Very Slow and some times indefinite 2. Capacity of Chisel is limited by the Winch Capacity 3. It is highly Operator Oriented 4. Very High Quality Supervision Required 5. The Actual Rock in which Pile is socketed is assessed by indirect method- by energy input 6. Energy is Spent breaking the Entire Rock Mass within the

Socket Portion Inefficient Method27-11-2010 L&T-ECC Division : Dr.K.S.Rama Krishna : Piling in Difficult Ground, IGS, Madurai 22

Rock Socket Using Rotary Piling RigsBORE PILE CONSTRUCTION SEQUENCEBentonite (drilling fluid) filling Commence drilling

Drilling soil & rock

27-11-2010

L&T-ECC Division : Dr.K.S.Rama Krishna : Piling in Difficult Ground, IGS, Madurai

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BORE PILE CONSTRUCTION SEQUENCESolid Rock Core Extracted

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L&T-ECC Division : Dr.K.S.Rama Krishna : Piling in Difficult Ground, IGS, Madurai

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Working Sequence for Rock Socket Construction Kelly Drilling Method with Bentonite Mud

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L&T-ECC Division : Dr.K.S.Rama Krishna : Piling in Difficult Ground, IGS, Madurai

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27-11-2010

L&T-ECC Division : Dr.K.S.Rama Krishna : Piling in Difficult Ground, IGS, Madurai

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Koden Test For Verticality

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L&T-ECC Division : Dr.K.S.Rama Krishna : Piling in Difficult Ground, IGS, Madurai

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Cores for Concrete Quality

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L&T-ECC Division : Dr.K.S.Rama Krishna : Piling in Difficult Ground, IGS, Madurai

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Pile Toe-Rock Contact Ve

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