RE & RTO Seminar cum Awards Night

Supervision of Foundation Works

Chua Tong Seng14th December 2011

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Teamwork: QP-RE-RTO

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DTL

MCEKPE

KPE-C424KPE-C423LTA

Understanding Soil Condition

DSTA,2009

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Bukit Timah Granite Formation

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Bkt Timah

Granite

Kallang FormationMarine Clay

UMC

LMC

Dr.Poh, TY

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UMC

LMC

6000 years ago

E , F1 and F2

Fluvial Clay, F2

Estuarine Deposit, E

Estuarine Deposit, E

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Fluvial Sand, F1

Old Alluvium Formation

K.W.Lee,2010

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Sandy CLAY

Clayey SAND

Jurong Formation

Syncline

JF@Buona Vista

Geological Time, Kimura, 2011

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Limestone Formation

Jeyatharan et al, 2003

Vietnam,Yashuda, 2011

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?

Fort Canning Boulder Bed, FCBB

Shirlaw et al, 2003

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LONGITUDINAL SECTION

Types of Foundation

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Classification of Piles

End Bearing and Friction Piles Replacement,

Displacement or Low-displacement?

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Bored Piles in Singapore

GBH

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Sequence of Construction

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B

Keep Accurate Installation Records

• Soil Description

• Dry hole or tremie concreting

• Stabilisation method

• Length of temporary steel casing

• Duration of drilling

• Record of anomaly, like hole

collapse

• Pile concreting record

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Collection of Representative Samples

Collection of samples for various depths and different soil/rock layers Which sample do you choose?

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Construction Problems

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Chua, 1999

Stabilising Fluids

Bentonite suspension

Polymer suspension

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Marsh Funnel

Mud Balance

Construction tolerance: VerticalityCaliper Logging (Koden)

• Singapore Standard

CP4:2003, Code of

Practice for

Foundations

1:75

Kelly Bar

Loadtest,2011

Bauer,2011

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Eccentricity

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Where is the centre of pile ?

75mm

Time-Lag before Concreting

CP4:2003 Code of Practice for Foundation

• The time interval between completion of the

formation of the borehole and commencement

of concreting should be minimised as ground

will deteriorate with time

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Checking Base of Pile

LCH,2011

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Imperfection: Soft Toe of Pile

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Type of Rock at Founding Depth

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Slake Tests

Case 1 Case 2

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Reinforcements of Bored Pile

CP4: 2003, Foundations

• CP4: compression min main

reinforcement 0.5% of Ac

and not less than 10m long

below pile cut-off level

• For tension , full cage

• For pile within excavation,

reinforcement should be

adequately provided for

bending moment.

BS EN 1536:2000, Bored Piles

• Piles should be reinforced

over any length through

soft or loose soil

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Barrette Piles

BS EN 1536:2000

Dr. Yet,N.S., 2010

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Driven Piles

Pile Driver Pile Segments

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Common Problems with Driven Piles

Piles shorter than design

• Driving energy less than

required i.e. low hammer

efficiency or soft cushion

• Soil strength higher than

anticipated

Piles longer than design

• Driving energy higher than required

• Soil resistance lower than anticipated

• Additional piles to compensate weaker soil i.e. due higher negative skin friction, nsf ?

• Overstressing, yielding of piles?

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Overstressing of Steel Piles

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HKFellinius, 1986

Type of Pile Load Test

Ultimate Load Test

• Verification of design

• Conducted to 2.5 to 3.0

times working load, or

failure

• Instrumented to determine

skin friction and end

bearing

Working Load Test

• Quality control test for

assessment of workmanship

• Tested to 1.5 to 2.0 times

working load

• Randomly chosen from

among working piles, not

pre-selected

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(Dr. Yet NS, 2011)

BCA/IES/ACES Advisory Note 1/03 on

Load Tests and Schedule

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Method of Pile Load Tests

Kentledge Method O-Cell

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Foo HK,2011

Dynamic Pile Testing

High Strain Pile Dynamic Test, PDA Statnamic Test

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Pile Intergrity Testing

Cross-hole Sonic Logging Low Strain Hammer Test

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Guidelines for Pile Load Test using Kentledge

• Key points

� Design by PE

� Kentledge weight at least 110% of max test load

� Supervise by PE and QSS

� Design to Codes and prepare Drawings to communicate design intent

� Construction to follow design Drawings

� Instrumentation and monitor stability

� All to observe WSHA

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Workplace Safety & Health Act, WSHA

• An ACT relating to safety, health and welfare of persons at work in workplaces

• WSH(Construction) Regulations 2007

– Piling works

– Reg. 129 Stability of adjacent structures

– Reg. 130 Inspection

– Reg. 131 Pile driver not in use

– Reg. 132 Pile testing

– Reg. 133 Footing

Lim Shiyi, 2011

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Source of Specification

• Projects Technical Specification

• Code of Practice SS CP4:2003 Foundation

• Code of Practice SS515:2005 Supervision of Structural Works

• Code of Practice BS EN– BS EN 1536:2000 Execution of special geotechnical works –

Bored piles

– BS EN 12699:2000 Execution of special geotechnical works –Displacement piles

– BS EN 14199:2000 Execution of special geotechnical works –Micropiles

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Conclusion

• Good for QP-RE-RTO to cultivate goodcommunication links. QP to disseminate keydesign requirements and RE-RTO to feedback onsite observations i.e. unexpected soil condition atthe site

• RE-RTO contributions are very important

• All should be familiar with relevant Codes

• Works as a Team. If there is any incident, the lineof responsibility will become irrelevant as allmembers in the team will be affected in one wayor another.

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