1. RE & RTO Seminar cum Awards Night
Supervision of Foundation Works
Chua Tong Seng
14th December 2011
1

2. Teamwork: QP-RE-RTO
2
DTL
MCEKPE
KPE-C424KPE-C423 LTA

3. Understanding Soil Condition
DSTA,2009
3

4. Bukit Timah Granite Formation
4
Bkt Timah
Granite

5. Kallang Formation
Marine Clay
UMC
LMC
Dr.Poh, TY
5
UMC
LMC
6000 years ago

6. E , F1 and F2
Fluvial Clay, F2
Estuarine Deposit, E
Estuarine Deposit, E
6
Fluvial Sand, F1

7. Old Alluvium Formation
K.W.Lee,2010
7
Sandy CLAY
Clayey SAND

8. Jurong Formation
Syncline
JF@Buona Vista
Geological Time, Kimura, 2011
8

9. Limestone Formation
Jeyatharan et al, 2003
Vietnam,Yashuda, 2011
9
?

10. Fort Canning Boulder Bed, FCBB
Shirlaw et al, 2003
10
LONGITUDINAL SECTION

11. Types of Foundation
11

12. Classification of Piles
End Bearing and Friction Piles Replacement,
Displacement or Low-displacement?
12

13. Bored Piles in Singapore
GBH
13

14. Sequence of Construction
14
B

15. 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
15

16. Collection of Representative Samples
Collection of samples for various
depths and different soil/rock layers Which sample do you choose?
16

17. Construction Problems
17
Chua, 1999

18. Stabilising Fluids
Bentonite suspension
Polymer suspension
18
Marsh Funnel
Mud Balance

19. Construction tolerance: Verticality
Caliper Logging (Koden)
• Singapore Standard
CP4:2003, Code of
Practice for
Foundations
1:75
Kelly Bar
Loadtest,2011
Bauer,2011
19

20. Eccentricity
20
Where is
the centre
of pile ?
75mm

21. 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
21

22. Checking Base of Pile
LCH,2011
22

23. Imperfection: Soft Toe of Pile
23

24. Type of Rock at Founding Depth
24

25. Slake Tests
Case 1 Case 2
25

26. 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
26

27. Barrette Piles
BS EN 1536:2000
Dr. Yet,N.S., 2010
27

28. Driven Piles
Pile Driver Pile Segments
28

29. 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?
29

30. Overstressing of Steel Piles
30
HKFellinius, 1986

31. 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
31
(Dr. Yet NS, 2011)

32. BCA/IES/ACES Advisory Note 1/03 on
Load Tests and Schedule
32

33. Method of Pile Load Tests
Kentledge Method O-Cell
33
Foo HK,2011

34. Dynamic Pile Testing
High Strain Pile Dynamic Test, PDA Statnamic Test
34

35. Pile Intergrity Testing
Cross-hole Sonic Logging Low Strain Hammer Test
35

36. 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
36

37. 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
37

38. 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
38

39. Conclusion
• Good for QP-RE-RTO to cultivate good
communication links. QP to disseminate key
design requirements and RE-RTO to feedback on
site observations i.e. unexpected soil condition at
the site
• RE-RTO contributions are very important
• All should be familiar with relevant Codes
• Works as a Team. If there is any incident, the line
of responsibility will become irrelevant as all
members in the team will be affected in one way
or another.
39