Requirements on piling plan submission

1 1Er Dr Yet Nai SongBuilding and Construction AuthorityRequirements on piling plan submissionUnder BC (Amendment) Act 2007 & Regulations 20082 Types of piling submissionsBored cast-in place pilesBarrettesGrouted micropiles3 Types of piling submissionsDriven pilesJacked-in piles4 Objective To help Qualified Persons who prepare the piling plans to comply with Requirements of BC (Amendment) Act 2007 & Regulations 20085 Overview1. submission checklist2. BC Regulations 10(2)3. SS CP4 : 20034. BCA / IES / ACES Advisory Note on Site investigation & Load test5. piling Annexes B, C, D6. Good practices in design & construction6(1) submission checklist7 submission plansendorsed by QP and reportsby QP and formsby QP and AC investigation report, endorsed & certified by a planshowing the layout and location of the site, boundary line and neighbouring buildings assessment report, where applicable (eg. for foundations located within influence zone of sensitive structures, like MRT or CST tunnels)VII.

2 Clearance letters, where applicable, from the relevant authority 8 Certifications by QP and AC on plans ACPE9 Certifications by QP(geo) and AC(geo) on plansAC(geo)PE(geo)1011 Certification by PE for SI report12 Plan to show Site LocationPlan to show Site LocationProposed Construction SiteSyedAlwiRdDeskerRdJalanBesarsiteSera ngoonRoad13An example of project close to sensitive structuresCST tunnelPile Raft for a 66-storey buildingPUB drainMRT stationCST tunnelMRT lines14(2) Building Control Regulation 10(2)15 Regulations 2003 Regulation 10(2)16 Regulations 2008 Regulation 10(2)the estimated pile penetration depth for each design zone ;the location of piles and site investigation boreholes ;17 Regulations 2008 Reg 10A(5)(Plans of foundation 30storeys)18 Building Control Regulations 2008 Regulation 10(2)the estimated pile penetration depth for each design zone ;the location of piles and site investigation boreholes ;19(a) Pile type & material specification, pile joints, sectional the plans show the pile typesand material specification?

3 The plans show pile sizeand pile details? 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 plan20 Pile capacity & Pile reinforcementPile diameterWorking loadPile reinforcement21 Details of Pile reinforcementAnchorage lengthLap lengthFull depth cage /12m cageSectional details22 Details of RC pileSectional detailsJoint detailsPilecap connection details23(b) Site investigation the plans show location of site investigation boreholes? there any borehole within the footprint of each block ?III. Do number of boreholesexceed minimum ? IV. Is depth of any boreholebeyond proposed pile penetration depth ? (see BCA/IES/ACES advisory note 2003)Items to be shown on piling planFor buildings of 10-storeys or more24 Site investigation boreholes (1)Footprint of tower blockTotal = 5 boreholes25 Total = 10 boreholesSite investigation boreholes (2)26 Site investigation boreholes (3)Total = 26 boreholes27(c) Pile depth & (d) Pile founding the plans show pile design zones(based on site investigation information) ?

4 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 to be shown on piling plan28 Pile design zones based on boreholes29 Example 1 Pile founding criteria (in hard soil)30 Example 2 Pile founding criteria (in hard soil & rock)31 Example 3 Pile founding criteria (pile set)32(e) Geotechnical the plans contain unit shaft frictionand unit pile base resistanceused for pile design ? soil strata / rock type given for the above ?Items to be shown on piling plan33 Unit shaft friction & base resistance used in pile design34(f) Negative skin there a design evaluationof the possibility of negative skin friction ?( whether the soil is still undergoing consolidation at its final stress state ?) negative skin friction been considered in the design?Items to be shown on piling plan35(g) Allowable allowable total and differential foundation settlementsshown on plan ?

5 These allowable foundation settlements consistent with the design calculation ?36 Sample variation of building settlement with time during superstructure erectionSettlement increases with building (h) Vibration allowable vibration limits specified on the plan ? 38 DIN 4150 : Part 3 Structural vibration in buildings Guideline on Limit of vibrationType 1 Type 2 Type 339(i) Verification the plans contain the following information ? (i) number of tests, (ii) types of pile types and number of tests provided complied with BCA/IES/ACES advisory note 2003 ? location of ultimate pile load testshown on plan, and correlated with borelog ? 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) 402 ULT + 5 WLT + 9 PDAE xceeded minimum !41 Preliminary pile to be instrumented42 Items to be shown on piling plana)Pile type & material specification, pile joints, sectional details b)Site investigation boreholesc)Estimated pile length for each design zoned)Minimum embedded depth into competent stratume)Skin friction & End bearing for pile designf)Pile capacity before & after negative skin frictiong)Allowable settlementsh)Allowable vibration limitsi)Pile load test & locationA recap43(3) SS CP4 : 2003(Code of Practice for Foundations)44 Code of Practice CP4 : 200345 Design for pile foundations[CP4 Clause ] Every pile design has to satisfy 3 conditions:1.

6 Adequate safety factor against failure2. Settlement of foundation under working load should not affect the serviceability of structure3. Safety of nearby buildings should not be put at risk46 Pile Group Effect(CP4 Clause ) settlement is greater than settlement of individual pile settlement between two pile groups < 1:50047300 nos piles within 60mx60m footprintAn example where pile group effect is dominant with overlapping of stress bulbs of individual piles48 Effect of lateral forces during basement excavation(CP4 Clause )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. 49An example of effect of basement excavation on foundation piles 15m excav Marine clay Dwall GMP 4 struts50 Table 1 Pile Ecc and Maximum Forces at Final Stage of ExcavationPile Position from Max eccMax NMax BM Max SFDwall [m][mm][kN][kNm][kN]RemarksL14202029615- 595in GMPL212181782488-346in GMPL32071753229-372in GMPR143623408201030in GMPR212303592-740357in GMPR320243255-645236in GMPF oundation piles move by 36mm, and experience bending moment of 820 kNm !

7 Foundation piles should be designed for the effect of basement (4) BCA / IES / ACES Advisory note(for buildings of 10-storeys or more)52 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 boreholesMinimum requirement to establish the soil strata and ground variation53 Example of soil profile for Bukit Timah formatio (1) Rockhead varies from RL 102m to RL88m(2) The quality of bedrock varies 5m into hard stratum54 Example of soil profile for Jurong FormationMin. 3 pile diameters below intended pile founding level55 Requirements for pile load tests2 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 should be used for bored piles)2 numbers or 1%of working piles installed or 1 for every 50 metreslength of proposed building, whichever is greater.

8 (b) Working load test1 number or the total piles whichever is greater.(a) Ultimate load teston preliminary pile (preferably instrumented)Pile Test ScheduleType of Load Test56 Load measurement for pile load tests(CP4 Clause ) Load should be measured by a calibrated load gauge& a calibrated pressure gauge57(5) piling Annexes(for buildings of 10-storeys or more)58 piling Annex BCertificate of supervision of pile load testQPBuilderSite supervisorQP(geo)59 piling Annex CInterim certificate of supervision of piling worksQPBuilderSite supervisorQP(geo)60 piling Annex DCertificate for monitoring building settlementSigned by QPSigned by QP(geo)61(6) Some good practices in pile design & construction62a) Reduce over-reliance on pile base resistance1) Applying a minimum safety factor to skin friction, for bored piles, where soft toe may occur63a) Reduce over-reliance on pile base resistance2) In erractic soil condition, eg limestone area35m3-m thick cavitylimestonelimestone64(b) Preliminary pile at borehole locationBoreholeUltimate test pile65(c)

9 Judicious location of strain gauges Taking into account :- change of soil layers- thickness- variability To aid interpretationeg. measurement of skin frictionat various soil /rock layers66(d) Innovative Investigative preliminary pile Preliminary piles may be formed with voids at base or soft toes to determine ultimate shaft resistanceCP4 Clause (e) Investigative preliminary piles installed using similar construction method as working production pilesDry hole methodWet hole methodCP4 Clause (f) Proper transfer of load to Kentledge frameUse stiffener for effective transfer 69g) Minimum distance between test pile & Kentledge leg Distance between Kentledge leg to surface of test pile m (CP4 Clause )70(h) No preloading on piles before test71 Pile SizeWorking LoadNosNo. ofMethod of(mm)(kN)Load TestTestASM-1350-100058001470-1200840099 1 Kentledge1500132001152 Kentledge1800190001593Bi-Directional2000 23500961Bi-Directional220028500881Bi-Dir ectional250036800621Bi-Directional280041 600221Bi-Directional300053000160-Total :93910(i) Conduct working load test at location where it mattersExamples : (1) Piles within the tower footprint(2) Piles carrying larger load72(j) No preselection of pile for working load test73(k) Keep rock/soil sample at site for verification74(l) Impose quality control measure at site1) Pile bore stability2) Pile base cleanliness3) Tests on stabilizing fluids75(l) Impose quality control measures at site4)Sufficient cooling time for weld to gain strength76(m) Check & verify obvious change in pile depthEg.

10 (1) Site investigation(2) Load tests77 Recap of Some Good Practicesa)Reduce over-reliance on pile base resistanceb)Preliminary pile at borehole locationc)Judicious location of strain gauges d)Innovative preliminary pilee)Preliminary pile installed using same method as working pilesf)Proper load transfer to Kentledgeframeg)Minimum distance between test pile & Kentledge legh)No preloading on piles before testi)Conduct working load test at location where it mattersj)No preselection of pile for working load testk)Check & verify obvious change in pile depthl)Keep soil/rock samples at site for verificationm)Impose quality control at site78 Summary1. Requirements of piling plan submission under recent BC amendment Act and Regulations2. Requirements for foundations of buildings more than 10-storeys3. Good practices in design, load tests & construction79 Concluding remark QP who prepare plans and calculations for piling plans have to comply with the Requirements of BC Act and regulationsStandard Certification by QP on plans and calculations I.