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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
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Understanding Soil Condition
DSTA,2009
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Bukit Timah Granite Formation
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Bkt Timah
Granite
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Kallang FormationMarine Clay
UMC
LMC
Dr.Poh, TY
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UMC
LMC
6000 years ago
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E , F1 and F2
Fluvial Clay, F2
Estuarine Deposit, E
Estuarine Deposit, E
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Fluvial Sand, F1
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Old Alluvium Formation
K.W.Lee,2010
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Sandy CLAY
Clayey SAND
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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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?
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Fort Canning Boulder Bed, FCBB
Shirlaw et al, 2003
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LONGITUDINAL SECTION
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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
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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
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Stabilising Fluids
Bentonite suspension
Polymer suspension
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Marsh Funnel
Mud Balance
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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
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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
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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)
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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
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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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