piling requirements
TRANSCRIPT
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Er Dr Yet Nai SongBuilding and Construction Authority
Requirements on piling plan
submissionUnder BC (Amendment) Act 2007 & Regulations 2008
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Types of piling submissions
Bored cast-in
place piles
Barrettes
Grouted
micropiles
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Types of piling submissions
Driven piles
Jacked-in
piles
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Objective
To help Qualified Persons whoprepare the piling plans to
comply with requirements of
BC (Amendment) Act 2007 &
Regulations 2008
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Overview1. Submission checklist
2. BC Regulations 10(2)
3. SS CP4 : 2003
4. BCA / IES / ACES Advisory Note on
Site investigation & Load test
5. Piling Annexes B, C, D
6. Good practices in design & construction
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(1) Submission
checklist
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Submission checklistI. Piling plans endorsed by QP and AC
II. Design reports by QP and AC
III. Declaration forms by QP and AC
IV. Site investigation report, endorsed & certified by a PE
V. A plan showing the layout and location of the site, boundaryline and neighbouring buildings
VI. Impact assessment report, where applicable (eg. for
foundations located within influence zone of sensit ive
structures, like MRT or CST tunnels)
VII. Clearance letters, where applicable, from the relevant authority
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Certifications by QP and AC on plans
AC
PE
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Certif ications by QP(geo) and AC(geo) on plans
AC(geo
)
PE(geo)
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Certification by
PE for SI report
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Plan to show Site LocationPlan to show Site Location
Proposed Construction SiteSyedA
lwiRd
DeskerRd
Jala
nBes
ar
site
Serango
on
Road
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An example of project close to sensitive structures
CST
tunnel
Pile Raft for a 66-storey building
PUB
drai
n
MRT
statio
nCST
tunnel
MRT lines
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(2) Building ControlRegulation 10(2)
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Regulations 2003Regulation 10(2)
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Regulations 2008
Regulation 10(2)
the estimated pile penetration depth for each design zone ;
the location of piles and site investigation boreholes ;
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Regulations 2008 Reg 10A(5)(Plans of foundation 30storeys)
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Building Control Regulations 2008Regulation 10(2)
the estimated pile penetration depth for each design zone ;
the location of piles and site investigation boreholes ;
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(a) Pile type & material specification, pilejoints, sectional details
I. Do the plans show the pile types and material specification ?
II. Do the plans show pile size and pile details?
III. Do the plans show the pile capacity ?
(i) allowable foundation capacity, before and after accounting
for negative skin friction,
(ii) allowable tension load, lateral load, where applicable.
Items to be shown on piling plan
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Pile capacity & Pile reinforcement
Pile diameterWorking load
Pile reinforcement
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Details of PilereinforcementAnchorage length
Lap length
Full depth cage /12m cageSectional details
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Details of RC pile
Sectional detailsJoint details
Pilecap connection details
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(b) Site investigation borehole
I. Do the plans show location of site
investigation boreholes?
II. Is there any borehole within the footprint ofeach block ?
III. Do number of boreholes exceed minimum ?
IV. Is depth of any borehole beyond proposedpile penetration depth ? (see BCA/IES/ACES
advisory note 2003)
Items to be shown on piling plan
For buildings of 10-storeys or more
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Site investigationboreholes (1)
Footprint of
tower block
Total = 5 boreholes
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Total = 10 boreholes
Site investigation
boreholes (2)
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Site investigation boreholes (3)
Total = 26 boreholes
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(c) Pile depth & (d) Pile founding criteria
I. Do the plans show pile design zones (based on
site investigation information) ?
II. Do the plans show the following information ?
(i) pile founding criteria (eg. pile founding depth /minimum embedment into competent stratum / pile
set criteria / magnitude of jack in load)
(ii) a description of soil / rock for founding layer.
Items to be shown on piling plan
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Pile design zones based on boreholes
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Example 1
Pile founding criteria (in hard soil)
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Example 2
Pile founding criteria(in hard soil & rock)
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Example 3
Pile founding criteria (pile set)
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(e) Geotechnical parameters
I. Do the plans contain unit shaft friction and unit
pile base resistance used for pile design ?
II. Are soil strata / rock type given for the above ?
Items to be shown on piling plan
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Unit shaft friction & base resistanceused in pile design
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(f) Negative skin friction
I. Is there a design evaluation of the
possibil ity of negative skin fr iction ?
(i.e. whether the soil is sti ll undergoing
consolidation at its final stress state ?)
II. Has negative skin friction been considered
in the design ?
Items to be shown on piling plan
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(g) Allowable settlements
I. Are allowable total and differential foundation
settlements shown on plan ?
II. Are these allowable foundation settlements
consistent with the design calculation ?
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Sample variation of building settlementwith time during superstructure erection
Settlement increases with building height.
10th 1.5mm
20th 3.0mm
30th 4.5mm
40th 6.5mm
43rd 8.0mm
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(h) Vibration limits
I. Are allowable vibration limits specified on
the plan ?
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DIN 4150 : Part 3 Structural vibration in
buildings Guideline on Limit of vibration
Type 1
Type 2
Type 3
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(i) Verification testsI. Do the plans contain the following information ?
(i) number of tests,
(ii) types of pile tests.
II. Are types and number of tests provided complied with
BCA/IES/ACES advisory note 2003 ?
III. Is location of ultimate pile load test shown on plan, andcorrelated with borelog ?
IV. Will the preliminary piles for the ultimate pile load test be
instrumented, to verify the geotechnical parameters ?
(Applicable to piles where strain gauges could be installed
along the pile, eg. bored piles, hollow spun pile)
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2ULT+5WLT+9PDA
Exceededminimum!
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Preliminary pile to be instrumented
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Items to be shown on pil ing plan
a) Pile type & material specification,
pile joints, sectional details
b) Site investigation boreholes
c) Estimated pile length for each
design zone
d) Minimum embedded depth into
competent stratum
e) Skin fr iction & End
bearing for pile design
f) Pile capacity before &
after negative skin friction
g) Allowable settlements
h) Allowable vibration limits
i) Pile load test & location
Arecap
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(3) SS CP4 : 2003
(Code of Practice for Foundations)
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Code of Practice
CP4 : 2003
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Design for pile foundations
[CP4 Clause 7.3.1]
Every pile design has to satisfy 3 conditions:
1. Adequate safety factor against failure
2. Settlement of foundation under working
load should not affect the serviceability ofstructure
3. Safety of nearby buildings should not be
put at risk
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Pile Group Effect
(CP4 Clause 7.3.4)
I. Group settlement is
greater than
settlement of
individual pile
II. Differential
settlement between
two pile groups
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300 nos 1.8m
piles within60mx60m
footprint
An example where pile group effect is dominant
with overlapping of stress bulbs of individual piles
Effect of lateral forces during basement excavation
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Effect of lateral forces during basement excavation
(CP4 Clause 7.4.5.3.2)
If bored piles are subject to lateral forces,
reinforcement should be adequately
provided for bending moments. to full pile length or
to where bending moment is negligible.
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An example of effect of basementexcavation on foundation piles
15m excav
Marine clay
Dwall GMP
4 struts
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Table 1 Pile Ecc and Maximum Forces at Final Stage of Excavation
Pile Position from Max ecc Max N Max BM Max SF
Dwall [m] [mm] [kN] [kNm] [kN] Remarks
L1 4 20 2029 615 -595 in GMP
L2 12 18 1782 488 -346 in GMP
L3 20 7 1753 229 -372 in GMPR1 4 36 2340 820 1030 in GMP
R2 12 30 3592 -740 357 in GMP
R3 20 24 3255 -645 236 in GMP
Foundation piles move by 36mm, and
experience bending moment of 820 kNm !
Foundation piles should be designed for
the effect of basement excavation.
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(4) BCA / IES / ACESAdvisory note
(for buildings of 10-storeys or more)
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Requirements for Site Investigation
- 5 metre into hard stratum with N>100
- 3 times pile diameters beyond pile
founding level.
(b) Depth of boreholes
- 1 borehole per 300 m2
- 1 borehole at 10 to 30m spacing
- Minimum 3 boreholes
(a) Number of boreholes
Minimum requirement
to establish the soil strata and ground variation
(1) Rockhead varies from RL 102m to RL88m
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xample of soil profile for Bukit Timah Formatio
(1) Rockhead varies from RL 102m to RL88m
(2) The quality of bedrock varies greatly.
Min. 5m into
hard stratum
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Example of soil profile for Jurong Formation
Min. 3 pile diameters below
intended pile founding level
Requirements for pile load tests
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q p
2 numbers or 2% of working piles
installed, whichever is greater.
(c) Non-destructive integrity
test. (Note: This is for the
purpose of quality control,
and high-strain type shouldbe used for bored piles)
2 numbers or 1% of working piles
installed or 1 for every 50 metres
length of proposed building,
whichever is greater.
(b) Working load test
1 number or 0.5% of the total piles
whichever is greater.
(a) Ultimate load test on
preliminary pile (preferably
instrumented)
Pile Test ScheduleType of Load Test
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Load measurement for pile load tests(CP4 Clause 7.5.5.2.1)
Load should be measured by a calibrated
load gauge & a calibrated pressure gauge
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(5) Piling Annexes(for buildings of 10-storeys or more)
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Piling Annex B
Certificate of
supervision of pile
load test
QP
Builder
Sitesupe
rvisor
QP(geo)
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Piling Annex CInterim certificate of
supervision of piling
works
QP
Builder
Sitesuperviso
r
QP(geo)
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Piling Annex DCertificate for
monitoring building
settlement
Sign
edby
QP
Signed
byQP
(geo)
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(6) Some good practices inpile design construction
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a) Reduce over-reliance on pile base resistance1) Applying a minimum safety factor to skin friction,
for bored piles, where soft toe may occur
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a) Reduce over-reliance on pile base resistance2) In erractic soil condition, eg limestone area
35m
3-m thick cavity
limestone
limestone
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(b) Preliminary pile at borehole locationBoreholeUltimate test p ile
( ) J di i l ti f t i
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(c) Judicious location of strain gauges
Taking into account :
- change of soil layers
- thickness
- variability
To aid interpretation
eg. measurement of skin frict ion
at various soil /rock layers
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(d) Innovative Investigative preliminary pile
Preliminary piles may be
formed with voids at base or
soft toes to determine
ult imate shaft resistance
CP4 Clause 7.5.4.1
( ) I ti ti li i il i t ll d i i i l
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(e) Investigative preliminary piles installed using similar
construction method as working production piles
Dry hole method
Wet hole method
CP4 Clause 7.5.4.1
(f) Proper transfer of load to Kentledge frame
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(f) Proper transfer of load to Kentledge frame
Use stiffener for effective transfer
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g) Minimum distance between test pile & Kentledge leg
Distance between Kentledge leg to surface of test pile
1.3 m (CP4 Clause 7.5.5.2.1)
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(h) No preloading on piles before test
(i) C d t ki l d t t t l ti h it tt
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Pile Size
Working
Load Nos No. of Method of
(mm) (kN) Load Test Test
ASM - 135 0 -
1000 5800 147 0 -
1200 8400 99 1 Kentledge
1500 13200 115 2 Kentledge
1800 19000 159 3 Bi-Directional
2000 23500 96 1 Bi-Directional
2200 28500 88 1 Bi-Directional
2500 36800 62 1 Bi-Directional
2800 41600 22 1 Bi-Directional
3000 53000 16 0 -
Total : 939 10
(i) Conduct working load test at location where it matters
Examples :
(1) Piles within the tower footprint
(2) Piles carrying larger load
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(j) No preselection of pile for working load test
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(k) Keep rock/soil sample at site for verification
(l) Impose quality control measure at site
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1) Pile bore stability
2) Pile base cleanliness
3) Tests on stabilizingfluids
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(l) Impose quality control measures at site
4) Suff icient cooling t ime forweld to gain strength
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(m) Check & verify obvious change in pile depth
Eg:
(1) Site investigation
(2) Load tests
Recap of Some Good Practices
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a) Reduce over-reliance on pile baseresistance
b) Preliminary pile at borehole location
c) Judicious location of strain gauges
d) Innovative preliminary pile
e) Preliminary pile installed using same
method as working piles
f) Proper load transfer to Kentledge
frame
g) Minimum distance between test pi le &
Kentledge leg
h) No preloading on piles before test
i) Conduct working load test at
location where it matters
j) No preselection of pile for working
load test
k) Check & verify obvious change in
pile depth
l) Keep soi l/rock samples at site for
verification
m) Impose quality control at site
Summary
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1. Requirements of piling plan submission
under recent BC amendment Act and
Regulations
2. Requirements for foundations of buildings
more than 10-storeys
3. Good practices in design, load tests &
construction
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Concluding remark
QP who prepare plans and calculations
for piling plans have to comply with the
requirements of BC Act and regulations
Standard Certification by QP on plans and calculations
I .... certify that they have been prepared in accordance with the provisions of
the Building Control Regulations, the Building Control Act and any otherwritten law pertaining to buildings and construction for the time being in
force.
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Thank you !
THE END