CONTENTSgnpgeo.com.my/download/publication/L2013_02.pdf · 2018-07-25 · • Advanced static cone...

1

G&P Geotechnics Sdn Bhd (G&P Geotechnics Sdn Bhd (www.gnpgroup.com.mywww.gnpgroup.com.my))

By Ir. Dr. Gue See Sew & Ir. Chow Chee Menghttp://www.gnpgeo.com.my

Quality Services Quality Services -- Our CommitmentOur Commitment©© G&P Geotechnics Sdn BhdG&P Geotechnics Sdn Bhd

CONTENTSCONTENTS• INTRODUCTION• OBJECTIVES• DESK STUDY• SITE RECONNAISSANCE• METHODS OF GROUND INVESTIGATION• FIELD TEST AND SAMPLING• PLANNING OF GROUND INVESTIGATION• SPECIFICATIONS• SUPERVISION

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INTRODUCTIONINTRODUCTION

Guidance notes to engineers on the practical aspect of site investigation

4



OBJECTIVESOBJECTIVESProvide adequate information for

- Site assessment, safe and economical designs of temporary and permanent works.

- Planning and assessment of construction method.

- Foresee construction difficulties.- Choice of site and layout

arrangement.

5

DESK STUDYDESK STUDY

Topographic Maps

Geological Maps & MemoirsSite Histories &

Landuse

Results of Adjacent &

Nearby Ground Investigation

Aerial Photographs

Details of Adjacent

Structures & Foundation

Topographic Map

6

Geological MapGeological Map

Aerial PhotographsAerial Photographs

7


1981..

Proposed Development

Aerial Photograph (22 years ago)Aerial Photograph (22 years ago)

8



1985..





1999..Residential

Residential

Residential

9


Aerial Photo Aerial Photo (2006)(2006)

60% of the site were located at sea



Earthworks in progress to form the site profile.

10



Reclamation Done



Current Site Profile Formed

11


SITE RECONNAISSANCESITE RECONNAISSANCE• Confirm and obtain additional

information.• Examine adjacent and nearby

development.• Compare the surface features and

topography with data obtainable in the desk study.

• Locate and study the outcrops, previous slips.


Exposed Pile

Settlement

Settling Platform Detached from Building

12



13



Vegetation

14


Vegetation


Vegetation at Site (Wall Failure Area)

15

G&P Geotechnics Sdn Bhd (G&P Geotechnics Sdn Bhd (www.gnpgroup.com.mywww.gnpgroup.com.my))

METHODS OF GROUND METHODS OF GROUND INVESTIGATIONINVESTIGATION


• Light Dynamic Penetrometer and Hand Auger

• Excavation and Borehole- Trial Pits- Sampling of soil and rock- Groundwater monitoring via Piezometer- SPT - Vane shear test

• Piezocone• Geophysical

16


LIGHT DYNAMIC PENETROMETERLIGHT DYNAMIC PENETROMETER

• JKR or Mackintosh probe- to obtain preliminary subsoil information.- limit to shallow depth.- drop of hammer should be free fall and

consistent drop height.

17

JKR OR MACKINTOSH PROBES


HAND AUGERHAND AUGER

- To determine soil type and ground water.- Depth ≤ 5m

18


EXCAVATIONEXCAVATION• To prospect fill materials or exposing

materials.• Only apply to shallow depth (≤ 5m)

- Safety Precautions

• Stability of sides / slopes• Barricades if the pit is needed for further

testing• Backfill and compact properly after use.


BOREHOLESBOREHOLES• Refer to BS 5930• Includes boring, sampling, in-situ testing

and water table observation.• Drill through soils and core through

rocks.• Two commonly used methods:

a) Rotary drilling methodb) Wash boring

• Rock Coring

19


Care in Boreholes

- levels and coordinates

- Samplers in good condition, clean & greased

- Samplers sealed, labelled & stored


20


Sizes of commonlySizes of commonly--used Core barrels, Casings and Drill used Core barrels, Casings and Drill Rods UsedRods Used

21

Typical Rotary Drilling RigTypical Rotary Drilling Rig


Sampling in BoreholesSampling in Boreholes• Wash Samples

- soil strata description

• Disturbed Samples- Split spoon samples from SPT

• Undisturbed Samples- Piston Sampler- Thin wall sampler- Continuous Sampler- Mazier Sampler

22

Piston SamplerPiston Sampler

- for very soft to soft cohesive soils with (SPT’ N’ < 2)

Thin Wall SamplerThin Wall Sampler

- for cohesive soils up to firm consistency (SPT’N’ < 10)

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Continuous SamplerContinuous Sampler

• To identify sand lenses, description and classification tests.

• Usually for soft marine deposits.

MazierMazier SamplerSampler- Three-tube core-barrels containing detachable liners within the inner barrel.

- Suitable for stiffer soil stratum.

24

Care in SamplingCare in Sampling

Staging for Borehole at Mud Flats

25


Sg. Kelang


Groundwater Groundwater • Water level should be taken daily during SI

(particularly in the morning).

• Piezometer should be used for accurate and longer time measurement.

• Good practice :1. Lower down water level in borehole 2. Allow the ground water rise to original

level 3. Collect the water samples.

26

Boreholes with Standpipe

Piezometers Lockable Cap to prevent vandalism

Bright Color (Red + White) to prevent vehicle knocking into it.

Borehole Number Clearly Marked on

Concrete

27


Standard Penetration Test (SPT)Standard Penetration Test (SPT)

• According to BS 1377

- Hammer weight = 63.5kg- Drop height = 760mm- Total penetration is 450mm and the

number of blows for the last 300mm is the SPT’ N’ value.

Care - depth of test vs casing L

*site supervision

Equipment for SPT

28


ERRORS CONSEQUENCE

Inadequate cleaning of borehole (X) N, sludge trapped in sampler Casing driven bottom of the borehole )(↑ N in sand & )(↓ N in clay Damaged tip of sampling spoons )(↑ N Loose joints on connecting rods )(↑ N Not using guide rod )(↑ N, eccentric blows Water level in borehole below ground water level

)(↓ N especially sand at bottom of borehole, piping effect

Note : Where N = SPT’N’ values, )(↓ = Giving misleading lower value, )(↑ = Giving misleading higher value, (X) = Wrong Results

Factors Affecting SPT (N) Factors Affecting SPT (N) ValuesValues


Field Vane Shear TestField Vane Shear Test

• To obtain in-situ undrained shear strength of very soft to firm clay (clay only).

• Standard rate of rotation:- 6 degrees or 12 degree per minute

• Sensitivity of the soil can be determined

• Correct calibration chart for the torque shall be used.

• Influence of rootlets and coarse particles may lead to misleading results.

29

Field Vane Shear DevicesField Vane Shear Devices


PiezoconePiezocone (CPTU)(CPTU)• Advanced static cone penetration

test.• Rapid and continuous measures of

soil profile ,strength and pore water pressure.

• Allow dissipation test and obtain consolidation parameters.

• Data are captured electronically on computer.

30

Detailed Terminology of Piezocone Typical Piezocone Rig


31

PiezoconePiezocone


PLANNING OF GROUND PLANNING OF GROUND INVESTIGATIONINVESTIGATION

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Stage 1 Stage 1 -- PreliminaryPreliminary• General subsoil profile

- Estimate earthwork and rock excavation- Typical soft areas, cut or fill.

• Preliminary confirmation of layout and formation levels.

• Preliminary soil parameters and water table.

• Conceptual design and preliminary cost estimation.


?

?

?

?

?

??

?? ?

?

Ground Conditions?

SHIFT

Limestone

33

S.I. In Grid PatternS.I. In Grid Pattern

(Total = 32 nos)

Not Recommended

Proposed SIProposed SI

(Total = 32 nos)

34

Typical CrossTypical Cross--SectionSection

Ground Level

Bedrock LevelVery Hard Material Level

Hard Material Level

Groundwater Level

EXISTING GROUND

LEVEL

Water Table

C’2, ø’2

Clayey Layer

C’3, ø’3

C’1, ø’1

BH

BH

BH Perched WT

Seepage

CROSS SECTION

35


Stage 2 Stage 2 –– Detailed InvestigationDetailed Investigation• Carry out after optimum building

layout is confirmed.• Refine subsoil profile and obtain soil

parameters.• Soft soil fill area• Major cut and slope• Structures

- Retaining wall- Loading areas


Selection of Ground Investigation Selection of Ground Investigation MethodsMethods

• Slope and cut area- use Boreholes- SPT and Mazier samples for triaxial tests- Piezometer

• Fill area / soft ground- use Boreholes and Piezocones- Vane shear tests for soft cohesive soil and

Mackintosh probe.- Undisturbed soil sampling for laboratory

strength and consolidation test

36

Staging for Borehole at Mud Flats

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38



Extent of Ground InvestigationExtent of Ground InvestigationIt depends on:

– Available information.– Geological formation and features.– Variability of subsoil and

groundwater.– Proposed structures and platforms.– Adjacent property.

39


Preliminary Ground InvestigationPreliminary Ground Investigation• Number/ Spacing (Minimum)• Depth

- Fill area (Compressible with SPT N≈ 30)- Cut Area (Depth of potential slips)

• Structures- up to depth of soil where the pressure

induced by structure has little influence (theoretically)

• Geophysical survey for large area and to determine bedrock profile and characteristics.

Depth of Investigation

Stability Analysis

Foundation Design

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Detailed Ground InvestigationDetailed Ground Investigation• Spacing

- Generally 10m to 30m for structures.- Intensified investigation for problem areas.- one at every pier and abutment for bridge.

• Depth of Rock CoringRock Type Minimum core length

Igneous rock 3m - 6m (expected boulders)Sedimentary ( x limestone) 3mLimestone ( x cavity) 10mLimestone with cavity 10m cavities free

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Depth of Rock CoringDepth of Rock Coring

• Boulder sizes (Granite formation):– Typically not exceeding 3m but cannot be

ruled out

G&P Geotechnics Sdn Bhd (G&P Geotechnics Sdn Bhd (www.gnpgroup.com.mywww.gnpgroup.com.my))G&P Geotechnics Sdn Bhd

Preboring through boulders

Boulders exposed

after preboring

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Depth of Rock CoringDepth of Rock Coring

• In tropical region such as Malaysia with high rainfall, possible cave widths of up to 10m possible (Waltham & Fookes, 2003)

• General guideline on stability of natural rock roof– Stable if the thickness of rock is equal to or

greater than its span

Quality Services Quality Services -- Our CommitmentOur Commitment©© G&P Geotechnics Sdn BhdG&P Geotechnics Sdn BhdCAVERN/CAVITY EXPOSED AFTER EXCAVATION

43



Laboratory Test

a) Classification- Sieve Analysis- Clay/Silt- Atterberg Limits- Moisture Content- Unit Weight- Specific Gravity

b) Compressibility- Consolidation- Swelling

c) Shear Strength

- Laboratory Vane- UCT- UU- Shear Box

Total

- CIU- CID

Effective

e) Chemical- SO4- CI- Ph- Resistivity- Redox Potential

d) Compaction Fill

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G&P-Form6 (Rev3) G&P GEOTECHNICS SDN. BHD.

(Geotechnical Consultants)

LABORATORY TEST SCHEDULE Project No : ……………………………….. Lab. Schedule No. ……………….. Requested by : …………………………………………… Date : ………………….. Project : ……………………………………………………………………………………..………………… Reviewed by : …………………………………………... Date : ……………………

BOREHOLE SAMPLE NO.

DEPTH m M/C A.L. B.D. S.G.

Direct Shear Box

SIEVE ANALYSIS CONSOLIDATION TRIAXIAL UCT

CHEMICAL ANALYSIS

Mech. Hydro. Std. Rapid S.S. CIU UU OR GANIC CONTENT PH SULPH ATE

CONTENT CHLORIDE CONTENT

TOTAL Requested

Performed

Note : 1) CIU - Isotropic Consolidated Undrained Triaxial Test with pore pressure measurements

- Use 70mm diameter sample (i.e. untrimmed Mazier sample) - Sample should not have side filter during consolidation - Shearing strain should be calculated using Cv values calculated during consolidation stage. - Multi-stage testing not allowed - P-Q Stress Path Plotting shall be submitted.

2) For CIU Tests, stress path and other relevant data shall be submitted in Hard Copy (Plots and Tabulated Data) and Soft Copy (Computer files data). Cell confining pressure of 0.5 σv, 1.0σv, 2.0σv shall be adopted

for the CIU test, where σv is the total vert ical in-situ stress. 3) UU - Unconsolidated Undrained Test (at total overburden pressure of the sample) 4) UCT - Unconfined Compression Test (untrimmed sample)

5) To determine Cv from Consolidation Tests :-

- Use Square-Root Time Method to determine d0.

- Then use Log-Time Method to determine d100

6) Direct shear box test - Three (3) reconstituted specimens (60mm x 60mm x 20mm thick) shall be used. - Applied normal stress pressure of 0.5 σv, 1.0σv, 2.0σv shall be adopted for the shear box test, where σv is the total vertical in-situ stress. 7) All specimens for triaxial or consolidation tests shall be obtained from center of the recovered samples in

UD sampler. 8) 2 moisture content tests shall be carried out on soil immediately besides the specimens retained for triaxial or consolidation tests. 9) Bulk density, particle size distribution and Atterberg Limit tests shall be carried out on every specimen after the triaxial or consolidation tests.


Special AttentionSpecial Attention

Triaxial Compression Test

- No/Minimum Trimming

- No Side Drains

- No Multistage

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SITE SUPERVISIONSITE SUPERVISION

• Full time Engineering Geologists, Engineers or experienced Technicians

• Briefing (Supervision Checklist)• Communication• Checklist (http://www.gnpgeo.com.my/RnD_spec_checklist_checklist.asp)


CONCLUSIONSCONCLUSIONS1. You pay for soil investigation whether

you carry out or not. In fact you eventually pay more without a soil investigation.

46


CONCLUSIONSCONCLUSIONSPrincipal conclusions:1. Delay and escalating

construction costs are due to inadequate site investigation

2. Consequences of inadequate SI is not only severe during design and construction stage but even more serious for full-life costing


CONCLUSIONS (CONCLUSIONS (concon’’tt))

2. You must know- why you wanted them- where they are to be carried out- how they should be done

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CONCLUSIONS (CONCLUSIONS (concon’’tt))

3. Use proper specifications

4. Full time supervision

5. Ensure QA/QC system.

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YOU PAY FOR SOIL YOU PAY FOR SOIL INVESTIGATION INVESTIGATION WHETHER YOU WHETHER YOU CARRY OUT OR CARRY OUT OR

NOTNOT

49


ReferenceReferenceMS 2038: 2006 – Code of Practice for Site Investigations MS 1754: 2004 – Code of Practice for EarthworksMS 1756: 2004 – Code of Practice for FoundationMS 1056: 2005 – Method of Test for Soils for Civil Engineering PurposesClayton, C.R.I. Simons, N.e. & Mathews, M. C. (1982) Site Investigation, A

Handbook for Engineers, Grenada London, 424PEuropean Group Subcommittee (1968)

“Recommended method of Static and Dynamic Penetration Tests 1965”Geotechnique Vol. 1 No. 1

Head, K. H. (1984)Manual of Soil Laboratory testing

GCO (1984) : Geotechnical Manual for Slopes, Geotechnical Control Office, Hong Kong

50

References (contReferences (cont’’d)d)GCO (1980) : Geoguide 2 : Guide to Site Investigation, Geotechnical Control

Office, Hong Kong

Gue, S. S. (1985)

“Geotechnical Assessment for Hillside Development”Proceedings of the Symposium on Hillside Development; Engineering Practice and Local By-Laws, The Institution of Engineers, Malaysia

Neoh, C. A. (1995)

“Guidelines for Planning Scope of Site Investigation for Road Projects”, Public Works Department, Malaysia

Ooi, T.A. and Ting, W.H. (1975)

“The Use of a Light Dynamic Cone Penetrometer in Malaysia”. Proceeding of 4th Southeast Asian Conference on Soil Engineering, Kuala Lumpur, pp. 3-62, 3-79

Ting, W.H. (1972)

“Subsurface Exploration and Foundation Problems in the Kuala Lumpur Area”, Journal of Institution of Engineers, Malaysia, Vol. 13, pp. 19-25

G&P Geotechnics Sdn Bhd

byby Ir. Dr. Gue See Sew & Ir. Chow Chee MengIr. Dr. Gue See Sew & Ir. Chow Chee Meng

INTERPRETATION OF INTERPRETATION OF LABORATORY AND LABORATORY AND

FIELD TEST RESULTS FIELD TEST RESULTS FOR DESIGNFOR DESIGN

http://www.gnpgroup.com.myhttp://www.gnpgroup.com.my

CONTENTSCONTENTS1. INTRODUCTION2. OBJECTIVE3. SCOPE4. INTERPRETATION

5. DESIGN PARAMETER

6. LABORATORY TEST

JKR PROBEJKR PROBESPTSPT


INTRODUCTIONINTRODUCTIONNEED

Neglected topic; only briefly covered in universities

Danger of using results directly without interpretation

Decision on choice of values for soil parameters

SCOPECommon tests only

PROCESSESSpecifications, Supervision, Presentation & Interpretation




Proton Iswara


Ferrari

OBJECTIVESOBJECTIVES

1) Illustrate the importance of interpretation

2) Show methods of compiling results and recognising errors


SCOPESCOPECommon field and laboratory tests

FIELD TESTSFIELD TESTSJKR/ Mackintosh probe

SPT (Standard Penetration Test)

Piezocone

Field Vane Shear

LABORATORY TESTSLABORATORY TESTSUnconfined compression

Triaxial Test (UU, CIU with pore pressure measurement & CD)

Consolidation

Geonor vane



JKR ProbesJKR ProbesPrimitive tool

Limited useShallow bedrock profile (limestone with slump zone)

Weak zone at shallow depth

Shallow foundation• No recent fill and future settlement

• Structure of low risk

• If in doubt – use borehole



Cased hardened steel pointer of Cased hardened steel pointer of 25mm dia. and 6025mm dia. and 60oo cone.cone.

12mm dia. HY 12mm dia. HY 55C steel rod55C steel rod

Prevent buckling during driving

5kg drop 5kg drop hammerhammer

22mm outer 22mm outer dia. couplingdia. coupling

28

•• ApparatusApparatus


CONE PENETROMETER


For practical application:

- Results of JKR Probe and Mackintosh Probe can be taken as equivalent

- JKR Probe created as equivalent to Mackintosh Probe as Mackintosh Probe is patented in the early days


•• Precautionary measuresPrecautionary measuresFree fall and consistent drop heightFree fall and consistent drop height

Components and apparatus properly Components and apparatus properly washed and oiledwashed and oiled

•• Termination criteriaTermination criteriaBlows/300mmBlows/300mm(maximum 400 blows/300mm)(maximum 400 blows/300mm)

Max 15m depthMax 15m depth


•• Typical test resultsTypical test results


Identifying localised soft/weak or slip plane.Identifying localised soft/weak or slip plane.

•• ApplicationsApplications


Identifying localised soft/weak or slip plane.Identifying localised soft/weak or slip plane.

•• ApplicationsApplications


Identifying nonIdentifying non--compliance fill.compliance fill.

TT

T = compaction lift


Allowable Bearing Capacity V.S. J.K.R. Dynamic Cone Penetration Resistance (After Ooi & Ting, 1975) ** Conditions applied



•• Comparison between JKR probe and SPTComparison between JKR probe and SPT


0 100 200 300 400JKR Blows

12

8

4

0

Dep

th (m

)

JKR Plot

0 10 20 30 40 50SPT'N'

12

8

4

0

SPT'N' Plot


0 10 20 30 40SPT'N'

16

12

8

4

0

14

10

6

2

Dep

th (m

)

SPT'N' Plot

0 100 200 300 400JKR Blows

16

12

8

4

0

14

10

6

2

JKR Plot

Number of Blows per 300 mm

Dep

th F

rom

Gro

und

Sur

face

In M

eter

(m)


Shear Strength In kPa

Dep

th F

rom

Gro

und

Sur

face

In M

eter



Shallow depthShallow depth

Not for gravelly groundNot for gravelly ground

Human errors Human errors (e.g. wrong counting, non(e.g. wrong counting, non--consistent consistent drop height, exerting force to the drop hammerdrop height, exerting force to the drop hammer

Misleading results at greater depthMisleading results at greater depth

•• LimitationsLimitations

A popular testA popular testuseful for pile foundation design

Common errorsCommon errors


Standard Penetration Test (SPT)Standard Penetration Test (SPT)


63.5kg Hammer

760mmFree Fall

450mm

Split-Spoon Sampler

AW Rod



Driving Shoe

Split Barrel

•• OD = 50mm OD = 50mm •• ID = 35mm ID = 35mm •• Length ~ 650mmLength ~ 650mm

Split-Spoon Sampler


Seating drive

Test drive

SPTSPT--N ValueN Value


SPTSPT--N = x 300 = 143N = x 300 = 143

5 5 -- 10 10 -- 30 30 -- 20/30cm20/30cmSeating drive

Test drive

(30 + 20)(30 + 20)(75 + 30)(75 + 30)


Maximum blows to be applied In seating drive In test drive Soil 25 50 ‘Soft rock’ 25 100

BS1377: Part 9

Formation Level


CLAY

SAND

SILTY CLAY


Red

uced

Lev

el (f

t)




New Technology New Technology ……automaticautomatic

1)1)To obtain soil profile and stiffness To obtain soil profile and stiffness (strength) profile of the subsoil(strength) profile of the subsoil

2)2) To determine coefficient of To determine coefficient of consolidation of soilconsolidation of soil

3)3) Results can also be used directly Results can also be used directly for design (e.g. pile design)for design (e.g. pile design)


Piezocone (CPTu)Piezocone (CPTu)

Piezocone ResultsPiezocone Results


Piezocone ResultsPiezocone Results


Nk = 11-19

Lunne & Kleven (1981)

Nkt = 15

Gue & Tan (2000)



Cone factors related to plasticity index of the clays (After Dobie & Wong, 1990)


1. Sensitive, fine grained2. Organic soils – peats3. Clays – clay to silty clay4. Silt mixtures – clayey silt to silty clay5. Sand mixtures – silty sand to sandy silt6. Sands – clean sand to silty sand7. Gravelly sand to sand8. Very stiff sand to clayey sand (heavily overconsolidated or cemented)9. Very stiff fine grained (heavily overconsolidated or cemented)

Soil Behaviour Type Classification Charts for CPT(after Robertson, 1990)


1)1)Vane test in boreholeVane test in borehole

2)2) Geonor vaneGeonor vane

3)3) Lab vaneLab vaneUseUse-- To determine inTo determine in--situ undrained situ undrained

shear strength (Sshear strength (Suvuv) of soft clayey ) of soft clayey soilssoils


Vane Shear TestVane Shear Test


Most common errorsMost common errors-- Computation Computation –– spring factorspring factor-- Clay with organic materialsClay with organic materialsRecognise errorsRecognise errorsSummarise results with SSummarise results with Suu from from unconfined compression, UU and lab unconfined compression, UU and lab vane superimposedvane superimposedPlot Plot SSuvuv against PIagainst PI

PPoo’’Or SOr Suvuv against Pagainst Poo’’ then find then find

PPoo’’SSuvuv





Dep

th (f

t)

Shear Strength (lb/ft2)


Foundation DesignFoundation Design• Stability / Bearing Capacity• Settlement Prediction

Bearing CapacityBearing Capacity• Su• C’ and Φ’

Settlement PredictionSettlement Prediction• e vs Log10 p’ (mv, Cc)• cv (k)


Design ParametersDesign Parameters


LABORATORY TESTSLABORATORY TESTS

-- Why?Why?

-- Types of Tests!Types of Tests!

-- How?How?

-- Specifications?Specifications?(Load, Pressure, Time)(Load, Pressure, Time)


SPECIFICATIONSSPECIFICATIONS

A) Consolidation TestA) Consolidation Test1) Which samples are appropriate and suitable for the test?2) For consolidation test

- Load increment

- Pressure

} 0.5Po’ – 8Po’} or to} e 0.42eo~~

B) Triaxial testB) Triaxial test1) For triaxial tests

- Strain rate- Back pressure

Ref: Head, K. H (1984) Ref: Head, K. H (1984) -- Manual of soil Laboratory testingManual of soil Laboratory testingG&P Geotechnics Sdn Bhd

Special AttentionSpecial Attention

Triaxial Compression Test

- No/Minimum Trimming

- No Side Drains

- No Multistage


G&P-Form6 (Rev3) G&P GEOTECHNICS SDN. BHD.

(Geotechnical Consultants)

LABORATORY TEST SCHEDULE Project No : ……………………………….. Lab. Schedule No. ……………….. Requested by : …………………………………………… Date : ………………….. Project : ……………………………………………………………………………………..………………… Reviewed by : …………………………………………... Date : ……………………

BOREHOLE SAMPLE NO.

DEPTH m M/C A.L. B.D. S.G.

Direct Shear Box

SIEVE ANALYSIS CONSOLIDATION TRIAXIAL UCT

CHEMICAL ANALYSIS

Mech. Hydro. Std. Rapid S.S. CIU UU OR GANIC CONTENT PH SULPH ATE

CONTENT CHLORIDE CONTENT

TOTAL Requested

Performed

Note : 1) CIU - Isotropic Consolidated Undrained Triaxial Test with pore pressure measurements

- Use 70mm diameter sample (i.e. untrimmed Mazier sample) - Sample should not have side filter during consolidation - Shearing strain should be calculated using Cv values calculated during consolidation stage. - Multi-stage testing not allowed - P-Q Stress Path Plotting shall be submitted.

2) For CIU Tests, stress path and other relevant data shall be submitted in Hard Copy (Plots and Tabulated Data) and Soft Copy (Computer files data). Cell confining pressure of 0.5 σv, 1.0σv, 2.0σv shall be adopted

for the CIU test, where σv is the total vert ical in-situ stress. 3) UU - Unconsolidated Undrained Test (at total overburden pressure of the sample) 4) UCT - Unconfined Compression Test (untrimmed sample)

5) To determine Cv from Consolidation Tests :-

- Use Square-Root Time Method to determine d0.

- Then use Log-Time Method to determine d100

6) Direct shear box test - Three (3) reconstituted specimens (60mm x 60mm x 20mm thick) shall be used. - Applied normal stress pressure of 0.5 σv, 1.0σv, 2.0σv shall be adopted for the shear box test, where σv is the total vertical in-situ stress. 7) All specimens for triaxial or consolidation tests shall be obtained from center of the recovered samples in

UD sampler. 8) 2 moisture content tests shall be carried out on soil immediately besides the specimens retained for triaxial or consolidation tests. 9) Bulk density, particle size distribution and Atterberg Limit tests shall be carried out on every specimen after the triaxial or consolidation tests.



Consolidation SettlementConsolidation Settlement

CONSOLIDATION TEST RESULTS

Void Ratio

Cv m²/year

Coefficient of Volume Change

Mv X 10ˉ³ m² / KN


Dep

th (m

)


Compression Index

Coefficient of Consolidation, Ch m²/yr

Dep

th (m

)




NAVFAC DM7.1

Log time methodRoot time method


Compression index, CCompression index, Ccc and and Recompression index, CRecompression index, Crr

a) a) CCcc = 0.009 (LL = 0.009 (LL –– 10%)10%) For inorganic soils,For inorganic soils,with sensitivity less with sensitivity less than 4than 4

b) b) CCcc = 0.007 (LL = 0.007 (LL –– 10%)10%) For normally For normally consolidated clayconsolidated clay

c) c) CCcc = 0.0115 W= 0.0115 Wnn For organic soils, peatFor organic soils, peat

d) d) CCcc = 1.15 (e= 1.15 (eoo –– 0.35)0.35) For all claysFor all clays

e) e) CCcc = (1 + e= (1 + eoo) [0.1 + (W) [0.1 + (Wnn –– 25)0.006]25)0.006] For varved claysFor varved clays

f) f) CCcc = 0.5*PI*G= 0.5*PI*Gss For OC claysFor OC clays

Compression index, CCompression index, Ccc and and Recompression index, CRecompression index, Crr

•• For inorganic normally For inorganic normally --consolidated Klang Clay (Tan et consolidated Klang Clay (Tan et al., 2004):al., 2004):–– CCcc = 0.02LL = 0.02LL –– 0.870.87–– CCcc = 0.61e= 0.61eoo –– 0.170.17–– CCcc = 0.02 W= 0.02 Wnn –– 0.370.37

•• CCrr ≈≈ (0.1 to 0.2)*C(0.1 to 0.2)*Ccc

Coefficient of secondary compression, CCoefficient of secondary compression, Cαα

•• CCαα / C/ Ccc = 0.04 = 0.04 ±± 0.010.01 For inorganic soft claysFor inorganic soft clays

•• CCαα / C/ Ccc = 0.02 = 0.02 ±± 0.010.01 For granular soils including For granular soils including rockfillrockfill

•• CCαα / C/ Ccc = 0.03 = 0.03 ±± 0.010.01 For shale and mudstoneFor shale and mudstone

•• CCαα / C/ Ccc = 0.05 = 0.05 ±± 0.010.01 For organic clays and siltsFor organic clays and silts

•• CCαα / C/ Ccc = 0.06 = 0.06 ±± 0.010.01 For peat and muskegFor peat and muskeg

TWO Major Categories :

(1)(1) Strength Parameters :Strength Parameters :

-- Stability Analyses of Slopes & Embankment.Stability Analyses of Slopes & Embankment.

-- Bearing Capacity Analyses for Foundation.Bearing Capacity Analyses for Foundation.

(2)(2) Stiffness & Deformation Parameters :Stiffness & Deformation Parameters :Prediction & evaluation of :Prediction & evaluation of :--Settlement, Heave, Lateral deformation, Settlement, Heave, Lateral deformation, Volume Change.Volume Change.

Interpretation of Laboratory TestsInterpretation of Laboratory Tests



Conventional Foundation for Low Rise Buildings


Conventional Foundation for Low Rise Buildings (Soil Settlement)


Exposed Pile

Settlement



TWO Conditions :

(A)(A) Total Stress :Total Stress :

-- For Short Term Conditions in Cohesive Soils.For Short Term Conditions in Cohesive Soils.

-- Little of no drainage. Little of no drainage.

(B)(B) Effective Stress :Effective Stress :-- For Long Term & Permanent Conditions.For Long Term & Permanent Conditions.

-- Fully Fully ““DrainedDrained”” Conditions.Conditions.

Strength ParametersStrength Parameters


Simple CheckSimple Check

qqallowallow = (N= (Ncc..ssuu / FOS)/ FOS)qqallowallow == allowable bearing pressure allowable bearing pressure

= = ((γγfillfill.H + 10) .H + 10) (( in kPain kPa))

NNcc == 55

HHfailurefailure = (5 x Su) / = (5 x Su) / γγfillfille.g. :e.g. :When When Su = 10 kPa ; Su = 10 kPa ; γγfill fill = 18 kN/m= 18 kN/m33

HHfailurefailure = (5 x 10)/ 18 = 2.8 m= (5 x 10)/ 18 = 2.8 mG&P Geotechnics Sdn Bhd

Clough et al. (1989)

Excavation: Check Depth of ExcavationExcavation: Check Depth of Excavation


Undrained Shear Strength, su from :

(i)(i) Unconfined Compression Test, UCTUCT

(ii)(ii) Unconsolidated Undrained Triaxial Test, UUUU

(iii)(iii) Laboratory Vane Shear TestLaboratory Vane Shear Test

Total Stress Strength, Total Stress Strength, ssuu



Typical Set-up of Triaxial Test

a)Base

b)Removable cylinder and top cap

c)Loading ram

d)Rubber membrane

Equipment for Triaxial TestEquipment for Triaxial Test

Effective Stress StrengthEffective Stress StrengthParameters c’ & φ’ Interpretation from

(i)(i) Isotropic Consolidated Undrained Triaxial Test, CIU + CIU + ΔΔUU

(ii)(ii) Isotropic Consolidated Drained Triaxial Test, CIDCID

(iii)(iii) Laboratory Shear Box Test Laboratory Shear Box Test (at v. slow (at v. slow rate)rate)

Note : Advantage to use Stress PathNote : Advantage to use Stress PathG&P Geotechnics Sdn Bhd

Mohr-Coulomb


Stress Path InterpretationStress Path InterpretationTwo types of Plot

(i)(i) MIT MIT Stress Path Plot Stress Path Plot (T.W. Lambe of MIT, 1967)

(ii)(ii) Cambridge Cambridge Stress Path Plot Stress Path Plot

The vertical axis : t = (σ1 - σ3)/2 = (σ’1 - σ’3)/2The horizontal axis :s = (σ1 + σ3)/2 & s’ = (σ’1 + σ’3)/2

(Roscoe, Schofield and Wroth (1958) at the Cambridge, England)The vertical axis :

q = σ1 - σ3 = σ’1 - σ’3The horizontal axis :p = (σ1 + σ2 + σ3)/3 & p’ = (σ’1+ σ’2+σ’3)/3

G&P Geotechnics Sdn BhdTerminology & Interpretation

MIT & Cambridge Stress Path PlotMIT & Cambridge Stress Path Plot

MIT & Cambridge Stress Path PlotMIT & Cambridge Stress Path Plot

Tan θ = t’ / sTan θ = Sin φ’K = c’ Cos φ’

C’ = KCos φ’

Tan η = q / p’Sin φ’ = (3 η) / ( 6 + η )r = c’ (6 Cos φ’) / (3 – Sin φ’)

C’ =r (3 – Sin φ‘)

6 Cos φ’


For Slopes & Walls AnalysesFor Slopes & Walls AnalysesParameter cParameter c’’ and and φφ’’ shall be shall be Interpreted fromInterpreted from

i)i) Isotropically Consolidated Undrained Isotropically Consolidated Undrained Triaxial Test, CIU + Triaxial Test, CIU + ΔΔuu

ii)ii)Isotropically Consolidated Drained Isotropically Consolidated Drained Triaxial Test, CIDTriaxial Test, CID

iii)iii)Laboratory Shear Box Test (at very Laboratory Shear Box Test (at very slow rate)slow rate)

Note: Advantage to use Stress PathNote: Advantage to use Stress Path


Large Strain


Scattered CIU Results

0 50 100 150 200 250 300 350 400 450 500s' = (σ1'+σ3')/2

0

50

100

150

200

250

300

350

400

450

500

t' =

(σ1'

- σ3')

/2

BH1 UD2BH2 UD1BH2 M1BH3 UD2BH4 UD1BH5 M1BH6 M1BH6 M2BH9 M1BH10 UD1BH10 UD3

0 50 100 150 200 250 300 350 400 450 500

0

50

100

150

200

250

300

350

400

450

500

Upper Boundc’ = 5 kPa, φ’ = 39º

Lower Boundc’ = 0 kPa, φ’ = 29º

Proposed Design Linec’ = 3.5 kPa, φ’ = 32º

φ’ = sin-1 mc’ = a / (cos φ’)

a

1m


Correlations for Preliminary Assessment of φ’


φφ’’ Values vs Plasticity IndexValues vs Plasticity Index (after Terzaghi)(after Terzaghi)

Typical PI = 30% to 70%(Malaysia Soft Clay)G&P Geotechnics Sdn Bhd

ΦΦ’’ Values vs Clay ContentValues vs Clay Content (Skempton, 1964)(Skempton, 1964)


ΦΦ’’ vs % of Finesvs % of Fines

Figure 3 : φ’peak versus Percentage of Fines in Residual Soils

30

35

25


cc’’ vs % of Finesvs % of Fines

Figure 4 : c’ versus Percentage of Fines in Residual SoilsG&P Geotechnics Sdn Bhd

Correct InterpretationCorrect Interpretation

Undrained Shear StrengthUndrained Shear Strength

•• Limitations of UU Tests:Limitations of UU Tests:–– Sample disturbanceSample disturbance–– Negative pore pressures generated during Negative pore pressures generated during

removal of sample from tuberemoval of sample from tube

•• Undrained shear strength is best Undrained shear strength is best obtained from inobtained from in--situ testing such as situ testing such as field vane, piezocone, etc.field vane, piezocone, etc.

YOU PAY FOR YOU PAY FOR SOIL SOIL INVESTIGATIONINVESTIGATIONWHETHER YOU WHETHER YOU CARRY OUT OR CARRY OUT OR

NOTNOT



REFERENCESREFERENCESASTM, (1986)

Standard Test Method for Deep Quasi-static, Cone and Friction Cone Penetration Tests of Soil, D3441-86, ASTM Committee D-18 on Soil and Rock, USA

Dobie, M.J.D., & Wong, J.T.F. (1990)“Piezocone testing; Interpretation in Malaysia Alluvial Clays” Geotechnical Aspects of the North-South Expressway, PLUS & PL, Kuala Lumpur

Fleming, W.G.K. et al (1985)Piling Engineering Survey University Press, Glasgow

International Society for Soil Mechanics and Foundation (1988)International Reference Test Procedure, ISSMFE Technical Committee on Penetration Testing, Proposal to ISSMFE, Orlando, USA

Head, K. H (1984)Manual of Soil Laboratory Testing


REFERENCESREFERENCES

Proceedings of 1st InternationalSymposium on Penetration Testing/ ISOPT – I/Florida, USA, 1988

Proceedings of 2nd EuropeanSymposium on Penetration Testing/ ESOPT – II/ Amsterdam/ May 1982

Robertson, P.K. and Campanella, R.G. (1988)Guidelines for using the CPT, CPTU and Marchetti DMT for Geotechnical Design, U.S. Department of Transportation, Federal Highway Administration, Office of Research and Special Studies, Report No. FHWA-PA-87-023+84-24

Meigh, A.C. (1987)Cone Penetration Testing: Methods and Interpretation, Construction Industry Research and Information Association, CIRIA Ground Engineering Report: In-site Testing, London


Sanglerat, G, (1972)The Penetrometer and Soil Exploration, Elsevier Publishing Company, Amsterdam, Netherlands

Teh, C.I. and Houlsby, G.T. (1991)An Analytical Study of the Cone Penetration Test in Clay, Geotechnique, Vol. 41, No. 1, pp: 17-34

REFERENCESREFERENCES

Gue, S.S. & Tan, Y.C. (2003)Current Status & Future Development of Geotechnical Engineering Practice in Malaysia, 12th ARC on Soil Mechanics & Geotechnical Engineering, Singapore

Gue, S.S. & Tan, Y.C. (2006)

Landslides: Abuses of the Prescriptive Method, International Conference on Slopes, Malaysia


PILED FOUNDATION PILED FOUNDATION DESIGN & CONSTRUCTIONDESIGN & CONSTRUCTION

By Ir. Dr. Gue See Sew & Ir. Chow Chee Menghttp://www.gnpgeo.com.my

ContentsContents

Overview

Preliminary Study

Site Visit & SI Planning

Pile Design

Pile Installation Methods

Types of Piles

Contents (ContContents (Cont’’d)d)Piling Supervision

Pile Damage

Piling Problems

Typical Design and Construction Issues

Myths in Piling

Case Histories

Conclusions

Overview

What is a Pile Foundation

It is a foundation system that transfers loads to a deeper and competent soil layer.

When To Use Pile Foundations

• Inadequate Bearing Capacity of Shallow

Foundations

• To Prevent Uplift Forces

• To Reduce Excessive Settlement

PILE CLASSIFICATIONPILE CLASSIFICATION

Friction Pile– Load Bearing Resistance derived mainly

from skin friction

End Bearing Pile– Load Bearing Resistance derived mainly

from base

Friction Pile

Overburden Soil Layer

End Bearing Pile

Rock / Hard Layer

Overburden Soil

Preliminary Study

Preliminary StudyPreliminary Study

Type & Requirements of Superstructure

Proposed Platform Level (ie CUT or FILL)

Geology of Area

Previous Data or Case Histories

Subsurface Investigation Planning

Selection of Types & Size of Piles

Previous Data & Case Previous Data & Case HistoriesHistories

Bedrock Profile

Existing Development

A

Existing Development

BProposed

Development

Only Need Minimal Number of Boreholes

Challenge The Norm Thru Innovation To Excel

SELECTION OF PILESSELECTION OF PILES

Factors Influencing Pile Selection– Types of Piles Available in Market (see Fig. 1)– Installation Method– Contractual Requirements– Ground Conditions (eg Limestone, etc)

– Site Conditions & Constraints (eg Accessibility)

– Type and Magnitude of Loading– Development Program & Cost– etc

TYPE OF PILES

DISPLACEMENT PILES NON-DISPLACEMENT PILES

TOTALLY PREFORMED PILES(A ready-made pile is driven or jacked

into the ground)

DRIVEN CAST IN-PLACE PILES(a tube is driven into ground to

form void)

Bored piles Micro piles

HollowSmall displacement

Solid

Steel Pipe Concrete Spun Piles

Concrete Tube

Closed ended tube concreted with tube left in position

Closed ended tube

Steel Tube

Open ended tube extracted while concreting (Franki)

Concrete Steel H-piles(small displacement)

Bakau pilesTreated timber pile

Precast R.C. piles

Precast prestressedpiles

FIG 1: CLASSIFICATION OF PILES

Restricted use due to environmental considerations

Caisson piles

BA

KA

U P

ILE

S

TIM

PE

R P

ILE

S

RC

PIL

ES

PS

C P

ILE

S

SP

UN

PIL

ES

STE

EL

H P

ILE

S

STE

EL

PIP

E P

ILE

S

JAC

KE

D P

ILE

S

<100 KN a a a ? ? ? ? a x ? a

100-300 a a a ? ? a a a x a a

300-600 ? a a a a a a a a a a

600-1100 x ? a a a a a ? a a ?

1100-2000 x ? a a a a a ? a a ?

2000-5000 x x a a a a a ? a a ?

5000-10000 x x a a a a a x a a x

>10000 x x ? a a a a x a ? x

<5m ? ? ? ? ? ? ? x a a ?

5-10m a a a a a a a ? a a a

10-20m ? ? a a a a a a a a a

20-30m x x a a a a a a a a a

30-60m x x a a a a a a a ? a

a a a a a ? a a a ? a

a a a a a a a a a ? a

? ? ? ? ? a a a ? a a

x x a a a a a ? a a ?x x ? ? ? a a ? a a ?x ? a a a a a a a a a

a a a a a a a a a ? a

a a a a a a a a a a a

? a a a a a a a a a a

x ? a a a a a a a a a


? a a a a a a a a a a

x ? a a a a a a a a a

V. DENSE SPT > 50 x x a a a a a ? a a ?

S < 100 mm x ? a a a a a a a a ?

100-1000mm x x ? ? ? a a ? a a x

1000-3000mm x x ? ? ? ? ? ? ? a x

>3000mm x x ? ? ? ? ? ? ? a x


x a a a a a a a a a a

a a ? ? ? ? ? a a a a

? ? ? ? ? ? ? a ? a a

1-2 0.5-2 1.5-3 1-2.5

AU

GE

RE

D P

ILE

S

COMPRESSIVE LOAD PER COLUMN

SC

ALE

OF

LOA

D

(STR

UC

TUR

AL)

1.0-3.5

PREVENTION OF EFFECTS ON ADJOINING STRUCTURES

(SUPPLY & INSTALL) RM/TON/M 0.5-2.5 0.3-2.0

LOOSE SPT < 10

UNIT COST

GROUND WATER

TYP

E O

F IN

TER

ME

DIA

TE L

AY

ER

GE

OTE

CH

NIC

AL TY

PE

OF

BE

AR

ING

LA

YE

RB

EA

RIN

G T

YP

E

ENVIRONMENT

MIC

RO

PIL

ES

BO

RE

D P

ILE

S

PREFORMED PILES

M. DENSE SPT = 10 - 30

MAINLY END -BEARING (D=Anticipated depth of bearing)

PARTLY FRICTION + PARTLY END BEARING

MAINLY FRICTION

LIMESTON FORMATION

M. STIFF SPT = 4 - 15

V. STIFF SPT = 15 - 32

HARD SPT > 32

DENSE / VERY DENSE SAND

SOFT SPT < 4

WEATHERED ROCK / SOFT ROCK

NOISE + VIBRATION; COUNTER MEASURES REQUIRED

BELOW PILE CAP

ROCK (RQD > 70%)

DENSE SPT = 30 - 50

COHESIVE SOIL

COHESIVELESS SOIL

SOIL WITH SOME BOULDERS / COBBLES (S=SIZE)

ABOVE PILE CAP

DESIGN CONSIDERATIONS

TYPE OF PILE

LEGEND :

8

x

?

INDICATES THAT THE PILE TYPE IS SUITABLEINDICATES THAT THE PILE TYPE IS NOT SUITABLE

INDICATES THAT THE USE OF PILE TYPE IS DOUBTFUL OR NOT COST EFFECTIVE UNLESS ADDITIONAL

MEASURES TAKEN

FIG 2 : PILE SELECTION CHART

Pile Selection Based on CostDetails: 250mm Spun Piles 300mm Spun Piles Micropile

Total Points 83 70 70

Average Length 9m 9m 9m

Average Rock Socket Length - - 2.5m

Indicative Rates :

Mob & Demob RM 50,000.00 RM 50,000.00 RM 20,000.00

Supply RM 33.00 / m RM 42.00 / m -

Drive RM 30.00 / m RM 32.00 / m -

Cut Excess, Dispose + Starter Bars RM 200.00 / Nos RM 200.00 / Nos -

Movement - - RM 200.00 / Nos

Drilling in Soil - - RM 110.00 / m

Drilling in Rock - - RM 240.00 / m

API Pipe - - RM 120.00 / m

Grouting - - RM 85.00 / m

Pile Head - - RM 150.00 / Nos

Est. Ave. Cost Per Point RM 967.00 / Nos RM 1,066.00 / Nos RM 4,297.50 / Nos

Est. Foundation Cost RM 190,261.00 RM 184,620.00 RM 380,825.00

√

Site Visit and SI Planning

Site VisitSite VisitThings To Look For …

Accessibility & Constraints of Site

Adjacent Structures/Slopes, Rivers, Boulders, etc

Adjacent Activities (eg excavation)

Confirm Topography & Site Conditions

Any Other Observations that may affect Design and Construction of Foundation

Subsurface Investigation (SI) Subsurface Investigation (SI) PlanningPlanning

Provide Sufficient Boreholes to get Subsoil Profile

Collect Rock Samples for Strength Tests (eg UCT)

In-Situ Tests to get consistency of ground (eg SPT)

Classification Tests to Determine Soil Type Profile

Soil Strength Tests (eg CIU)

Chemical Tests (eg Chlorine, Sulphate, etc)

Typical CrossTypical Cross--Section at Hill Site Section at Hill Site

Ground Level

Bedrock LevelVery Hard Material Level

Hard Material Level

Groundwater Level

EXISTING GROUND

LEVEL

Water Table

C’2, ø’2

Clayey Layer

C’3, ø’3

C’1, ø’1

BH

BH

BH Perched WT

Seepage

CROSS SECTION

Placing Boreholes in Limestone Areas

Stage 1 : Preliminary S.I.- Carry out geophysical survey (for large areas)

Stage 2: Detailed S.I. - Boreholes at Critical Areas Interpreted from Stage 1

Stage 3: During Construction- Rock Probing at Selected Columns to supplement Stage 2

Pile Design

PILE DESIGNPILE DESIGN

Allowable Pile Capacity is the minimum of :

1) Allowable Structural Capacity

2) Allowable Geotechnical Capacitya. Negative Skin Frictionb. Settlement Control

PILE DESIGNPILE DESIGNStructural consideration

• Not overstressed during handling, installation & in service for pile body, pile head, joint & shoe.

• Dimension & alignment tolerances (common defects?)

• Compute the allowable load in soft soil (<10kPa) over hard stratum (buckling load)

• Durability assessment

Pile Capacity Design Pile Capacity Design Structural CapacityStructural Capacity

Concrete Pile

Steel Pile

Prestressed Concrete Pile

QQallall = 0.25 x = 0.25 x ffcucu x Ax Acc

QQallall = 0.3 x = 0.3 x ffyy x Ax Ass

QQallall = 0.25 (= 0.25 (ffcucu –– PrestressPrestress after loss) x Aafter loss) x Acc

Qall = Allowable pile

capacity

fcu = characteristic strength

of concrete

fs = yield strength of steel

Ac = cross sectional area of

concrete

As = cross sectional area of

steel

SPT Blow Count per 300mm Penetration

Collection of SI DataCollection of SI Data

Pile Capacity Design Pile Capacity Design Geotechnical CapacityGeotechnical Capacity

4000 50 100 150 200 250 300 35026

24

22

20

18

16

14

12

10

8

6

4

2

0

12

10

8

6

4

2

00 50 100 150 200 250 300 350 400

Dep

th (m

)

Upper Bound

Lower Bound

Design Line (Moderately

Conservative)

Depth Vs SPT-N Blow Count

0 50 100 150 200 250 300 350 400

26

24

22

20

18

16

14

12

10

8

6

4

2

0

12

10

8

6

4

2

0

0 50 100 150 200 250 300 350 400

0 50 100 150 200 250 300 350 400

26

24

22

20

18

16

14

12

10

8

6

4

2

0

12

10

8

6

4

2

0

0 50 100 150 200 250 300 350 400

Upper Bound

Lower Bound

Design Line Upper Bound

Lower Bound Design Line

Dep

th (m

)



Dep

th (m

)



Collection of SI DataCollection of SI Data


Moderately Conservative Moderately Conservative Design ParametersDesign Parameters

Eurocode 7 definition:– Characteristic value of a geotechnical

parameter shall be selected as a cautious estimate of the value affecting the occurrence of the limit state

– In other words, moderately conservative

Moderately Conservative Moderately Conservative Design ParametersDesign Parameters

If at least 10 test results are available:

– A value of 0.5D below the mean of the test results provides a useful indication of the characteristic value

1. Contribution to Discussion Session 2.3, XIV ICSMFE, Hamburg, Balkema, Schneider H R (1997) – Definition and determination of characteristic soil properties. Discussion to ISSMFE Conference, Hamburg.

2. Extracted from Prof. Brian Simpson’s Course Note (2-day Course on Eurocode 7 Geotechnical Design to EC7, 13-14 November 2007, PJ, Malaysia).

Extracted from Prof. Brian Simpson’s Course Note (2-day Course on Eurocode 7 Geotechnical Design to EC7, 13-14 November 2007, PJ, Malaysia).

•• Piles installed in a group may fail:Piles installed in a group may fail:• Individually

• As a block


• Piles fail individually• When installed at large spacing


• Piles fail as a block• When installed at close spacing


Pile Capacity Design Pile Capacity Design Single Pile CapacitySingle Pile Capacity

Pile Capacity DesignPile Capacity DesignFactor of Safety (FOS)Factor of Safety (FOS)

Factor of Safety (FOS) is required for

Natural variations in soil strength & variations in soil strength & compressibilitycompressibility


Factor of Safety is (FOS) required for

Different degree of Different degree of mobilisationmobilisation for shaft for shaft & for tip& for tip Lo

adSettlement≈ 5mm

qsmob

qbmob

Load

Settlement≈ 5mm

qsmob

qbmob

Pile Capacity Design Pile Capacity Design Factor of Safety (FOS)Factor of Safety (FOS)

PartialPartial factors of safety for shaft & base factors of safety for shaft & base capacities respectivelycapacities respectively

For shaft, use 1.5 (typical)For shaft, use 1.5 (typical)

For base, use 3.0 (typical)For base, use 3.0 (typical)ΣQsu + Qbu

1.5 3.0Qall =


GlobalGlobal factor of safety for total ultimate factor of safety for total ultimate capacitycapacity

Use 2.0 (typical)Use 2.0 (typical)

ΣQsu + Qbu

2.0Qall =

Pile Capacity Design Pile Capacity Design Factor of Safety (FOS)Factor of Safety (FOS)

Calculate using Calculate using BOTHBOTH approaches approaches (Partial & Global)(Partial & Global)

Choose the Choose the lower lower of the of the QQallall valuesvalues

QQuu = Q= Qss + + QQbb


Qs = skin friction

Qb = end bearing

Qu = ultimate bearing capacity

Pile Capacity Design Pile Capacity Design Single Pile CapacitySingle Pile Capacity

Qu = α.sus.As + sub.Nc.Ab

Qsu Qbu

Qu = Ultimate bearing capacity of the pile a = adhesion factor (see next slide)sus = average undrained shear strength for shaftAs = surface area of shaft sub = undrained shear strength at pile baseNc = bearing capacity factor (taken as 9.0) Ab = cross sectional area of pile base

Pile Capacity Design Pile Capacity Design Single Pile Capacity : In Cohesive SoilSingle Pile Capacity : In Cohesive Soil

Pile Capacity DesignPile Capacity DesignSingle Pile Capacity:Single Pile Capacity: In Cohesive SoilIn Cohesive SoilAdhesion factor (Adhesion factor (αα) ) –– Shear strength (SShear strength (Suu) )

(McClelland, 1974)(McClelland, 1974)

Adhesion Factor

Su (kN/m2)25 75 100 125 150 17550

0

0.6

0.2

0.4

0.8

1.0

Cα/Su

Preferred Design Line

Meyerhof Fukuoka

SPT N fsu=2.5N(kPa)

su = (0.1+0.15N)*50

(kPa)α

fsu=α.su(kPa)

0 0 5 1 5

1 2.5 12.5 1 12.5

5 12.5 42.5 0.7 29.75

10 25 80 0.52 41.6

15 37.5 117.5 0.4 47

20 50 155 0.33 51.15

30 75 230 0.3 69

40 100 305 0.3 91.5

Correlation Between SPT N and Correlation Between SPT N and ffsusufsu vs SPT N

0

10

20

30

40

50

60

70

80

90

100

110

0 5 10 15 20 25 30 35 40 45

SPT N

fsu

(kP

a)

Meyerhof Fukuoka

Pile Capacity DesignPile Capacity DesignSingle Pile Capacity:Single Pile Capacity: In Cohesive SoilIn Cohesive Soil

Values of undrained shear strength, su can be obtained from the following:

Unconfined compressive test

Field vane shear test

Deduce based on Fukuoka’s Plot (minimum su )

Deduce from SPT-N values based on Meyerhof


NOTE: Use only direct field data for shaft friction prediction instead of Meyerhof

Modified Meyerhof (1976):

Ult. Shaft friction = Qsu ≅ 2.5N (kPa)

Ult. Toe capacity = Qbu ≅ 250N (kPa)

or 9 su (kPa)

(Beware of base cleaning for bored piles –

ignore base capacity if doubtful)


Modified Meyerhof (1976):Modified Meyerhof (1976):

Ult. Shaft Friction = Ult. Shaft Friction = QQsusu ≅≅ 2.0N (2.0N (kPakPa))

Ult. Toe Capacity= Ult. Toe Capacity= QQbubu ≅≅ 250N 250N –– 400N 400N

((kPakPa))

Pile Capacity DesignPile Capacity DesignSingle Pile Capacity:Single Pile Capacity: In In CohesionlessCohesionless SoilSoil

Note: Correlations for driven piles. Research by G&P indicates the correlations may be too conservative for jack-in piles

0 200 400 600

20

16

12

8

4

0

Dep

th (m

)

0 100 200 300 400 500Load (kN)

20

16

12

8

4

0

Pile Capacity DesignPile Capacity Design

ΣQsu

Qbu

ΣQsu + Qbu

0 200 400 600

20

16

12

8

4

0

Dep

th (m

)

0 100 200 300 400 500Load (kN)

20

16

12

8

4

0

0 200 400 600

20

16

12

8

4

0

Dep

th (m

)

0 100 200 300 400 500Load (kN)

20

16

12

8

4

0

0 200 400 600

20

16

12

8

4

0

Dep

th (m

)

0 100 200 300 400 500Load (kN)

20

16

12

8

4

0

ΣQsu + Qbu2.0

0 200 400 600

20

16

12

8

4

0

Dep

th (m

)

0 100 200 300 400 500Load (kN)

20

16

12

8

4

0

ΣQsu + Qbu1.5 3.0

SemiSemi--empirical Method (SPTempirical Method (SPT--N)N)Shaft : Shaft : ffsusu = = KKsusu ×× SPTSPT--NNTip Tip : : ffbubu = = KKbubu ×× SPTSPT--NN

From Malaysian experience:From Malaysian experience:

KKsusu = 2.0= 2.0KKbubu = 7.0 to 60 (depending on workmanship)= 7.0 to 60 (depending on workmanship)

Pile Capacity DesignPile Capacity DesignSingle Pile Capacity:Single Pile Capacity: For Bored PilesFor Bored Piles

Base cleaning of bored piles– Difficult and no practical means of verification

during construction avaliable

Base resistance require large movement to mobilise

Base contribution in bored pile design ignored unless proper base cleaning can be assured and verified (or base grouting, etc.)

Pile Capacity DesignPile Capacity DesignSingle Pile Capacity:Single Pile Capacity: For Bored PilesFor Bored Piles

ROCK SOCKET DESIGNROCK SOCKET DESIGN

Allowable Bearing Pressure on Rockqa = Ksp qu

qa = average bearing pressurequ = average unconfined compressive

strength of rockKsp = an empirical coefficient, which includes

a factor of 3 and ranges from 0.1 to 0.4

Ref: Canadian Foundation Engineering Manual

SPACING OF DISCONTINUITIES

SPACING WIDTH (m)*

APPROXIMATE RQD VALUE

Ksp

Moderately closeWideVery wide

0.3-11-3>3

≥ 25%≥ 75%≥ 90%

0.10.250.4

Bearing Capaciy of Rock Socket

1. Allowable Bearing Resistance on Rock Socket Base

qa = qu Kspdqu = average unconfined compressive strength of

rock coreKsp = empirical factor, and including a factor of 3

d = depth factor = 1 + 0.4 (Ls / Bs)≤ 3

where Ls = depth (length) of the socketBs = diameter of the socket

2. Allowable Shaft Resistanceqa = b β

Pa FOS

qu = Unconfined compressive strength of rock coreFOS = Factor of safety, generally 2Pa = Atmospharic pressure

b = an empirical factor (= 0.63 – lower bound, 1.42 – upper bound)β = rock mass fracturing factor

Combination of base and shaft resistance could only be considered when the base of pile could be cleaned with certainty

< < 0.05 fc

where fc = characteristics strength of concrete

paqu /

Allowable Shaft ResistanceAllowable Shaft ResistanceAPPROXIMATE RQD

VALUEβ

≥ 25%≥ 75%≥ 90%

0.40.60.9

Allowable Shaft ResistanceAllowable Shaft Resistance(EXAMPLE)(EXAMPLE)

Upper bound (b = 1.4)

Lower bound (b = 0.63)β = 0.6

Range of acceptable values – higher shaft resistance can be adopted if

verified by instrumented static load test results

Verification of Rock SocketVerification of Rock Socket

Recommended definition of rock coring shall fulfill all three (3) criteria below:

– Change of tools to rock coring tools, and


– The rock materials shall be verified by carrying out point load test on at least three (3) rock samples to achieve minimum index strength, Is(50) of 3 MPasubject to site confirmation on typical rock lump sizes based on the size correction factor, F = (De/50)0.45 where De is the equivalent core diameter in mm (Is(50) = F*Is), and


– The value of Is(50) varies for different rock formation and site conditions. Therefore, the Geotechnical Engineer designing the bored piles have to determine the proper value to be used as it is also related to rock socket capacity adopted for the bored piles.

Typical example of relationship

between UCT and Is(50)

- Specific for each site


- Recovered rock coring materials of more than 50% subject to site calibration upon start work unless otherwise agreed by the engineer.

Point Load Test

(UCS of Intact Rock)

End Bearing Design in RockEnd Bearing Design in Rock

Only designed when • Dry Hole• Base Cleaning & Inspection are possible

Pile Capacity Design Pile Capacity Design Block CapacityBlock Capacity

Qu = 2D(B+L) s + 1.3(sb.Nc.B.L)Where Qu= ultimate bearing capacity of pile groupD = depth of pile below pile cap levelB = width of pile groupL = length of pile groups = average cohesion of clay around groupsb = cohesion of clay beneath groupNc= bearing capacity factor = 9.0 (Refer to Text by Tomlinson, 1995)

Pile Capacity DesignPile Capacity DesignBlock Block Capacity:InCapacity:In Cohesive SoilCohesive Soil

No risk of group failure

if FOS of individual pile is adequate

Pile Capacity DesignPile Capacity DesignBlock Capacity:Block Capacity: In In CohesionlessCohesionless SoilSoil

No risk of block failure

if the piles are properly seated in the rock

formation

Pile Capacity DesignPile Capacity DesignBlock Capacity:Block Capacity: On RockOn Rock

Pile Capacity Design Pile Capacity Design Negative Skin Friction (NSF)Negative Skin Friction (NSF)

Compressible soil layer consolidates with time due to:

Surcharge of fillLowering of groundwater table

Pile Capacity DesignPile Capacity DesignNegative Skin FrictionNegative Skin Friction

Clay

FillOGL

1 2 30

Hf

ρsMonth


Pile to length (floating pile)Pile settles with consolidating soil NO NSF


Pile to set at hard stratum (end-bearing pile)

Consolidation causes downdrag forces on piles as soil settles more than the pile


Load

Load

Friction Pile –

Excessive Settlement

Load

End-Bearing Pile –

Crushing of Pile!!!

Positive Skin Friction

Pile Settlement >

Soil SettlementSoil Settlement > Pile Settlement

Negative Skin FrictionNegative Skin Friction

Negative

Skin

Friction

WARNING:No free fill by the contractor to avoid NSF


Effect of NSF Effect of NSF ……

Effect of NSF Effect of NSF ……

Reduction of Pile Carrying Capacity

NSF Preventive MeasuresNSF Preventive Measures

Avoid Filling

Carry Out Surcharging

Sleeve the Pile Shaft

Slip Coating

Reserve Structural Capacity for NSF

Allow for Larger Settlements

Clay

Sand

OGL

Qba

Qneg

SandFL

Clay

Sand

OGL

Qba

Qsu

Qall = (Qsu/1.5 + Qbu/3.0) - Qneg

Qsu

Qall = (Qsu/1.5 + Qbu/3.0)


70 60 50 40 30 20 10 0

Settlement (mm)100 0 -100 -200-300-400-500-600 -700 -800 -900-1000

Axial Compression Force (kN)

Settlement Curves &Axial Compression Force

14 May 9815 May 9818 May 9821 May 9804 Jun 9809 Jun 9819 Jun 9802 Jul 9813 Jul 98

0 10 20 30 40 50SPT-N (Blows/300mm)

BoreholeBH-1BH-2

Datum = 36.300m

40

35

30

25

20

15

10

5

0

Dep

th (m

, bgl

)

Increased Pile Axial LoadIncreased Pile Axial Load

Check: maximum axial load < structural pile Check: maximum axial load < structural pile capacitycapacity

Pile Capacity Design Pile Capacity Design Negative Skin FrictionNegative Skin Friction

Maximum axial load

Allowable working loadQult

FOS


Allowable working load

Qult

FOS(Qneg + etc)

Without Negative Skin Friction:

With Negative Skin Friction:

Pile Capacity DesignPile Capacity DesignStatic Pile Load Test (Piles with NSF)Static Pile Load Test (Piles with NSF)

• Specified Working Load (SWL) = Specified foundationload at pile head

• Design Verification Load (DVL) = SWL + 2 Qneg

• Proof Load: will not normally exceed

DVL + SWL

Pile Settlement DesignPile Settlement Design

Pile Settlement DesignPile Settlement DesignIn Cohesive SoilIn Cohesive Soil

Design for Design for total settlement & settlement & differential settlement for design settlement for design tolerancetoleranceIn certain casesIn certain cases, total settlement not an settlement not an issueissueDifferential settlement can cause settlement can cause damage to structuresdamage to structures

Pile Group Settlement in Clay

=

Immediate / Elastic Settlement + Consolidation

Settlement


Where

pi = average immediate settlement

qn= pressure at base of equivalent raft

B = width of the equivalent raft

Eu= deformation modulus

μ1, μ0= influence factors for pile group width, B at depth D

below ground surface

by by JanbuJanbu, , BjerrumBjerrum and and KjaernsliKjaernsli (1956)(1956)

IMMEDIATE SETTLEMENTIMMEDIATE SETTLEMENT


u

ni E

Bqp 01μμ=

μ1

μ0

Influence factors (after Janbu, Bjerrum and Kjaernsli, 1956)

IMMEDIATE SETTLEMENTIMMEDIATE SETTLEMENT


As per footing (references given later)

CONSOLIDATION SETTLEMENTCONSOLIDATION SETTLEMENT


No risk of excessive settlement

Pile Settlement DesignPile Settlement DesignOn RockOn Rock

Allowable Settlement of Allowable Settlement of BuildingBuilding

Settlement of high-rise building < 12mm or 25mm?

Myth or fact?

Actual Building SettlementActual Building Settlement

Actual recorded settlement of high-rise building– 20mm to 125mm

Important design considerations – NOT total settlement – Differential settlement governs

Definitions of foundation movement

Economical Design Economical Design of Highof High--Rise FoundationRise Foundation

Clause 2.3.2.4.3, BS8004 – Wind loading– …… foundations may be so

proportioned that the pressure due to combined dead load, live and wind loads does not exceed the allowable bearing pressure by more than 25%

FOUNDATION FOUNDATION CONSTRUCTIONCONSTRUCTION

Part 2

Pile Installation Methods

PILE INSTALLATION PILE INSTALLATION METHODSMETHODS

•Diesel / Hydraulic / Drop HammerDriving

•Jacked-In

•Prebore Then Drive

•Prebore Then Jacked In

•Cast-In-Situ Pile

Diesel Drop Hammer Driving

Diesel Drop Hammer Diesel Drop Hammer DrivingDriving

Hydraulic Hammer Driving

Hydraulic Hammer Hydraulic Hammer DrivingDriving

JackedJacked--In In PilingPiling

JackJack--in Pilesin Piles

Cast-In-Situ Piles

(Micropiles)

CastCast--InIn--Situ Situ Piles Piles

((MicropilesMicropiles))

Types of Piles

TYPES OF PILESTYPES OF PILES

•Treated Timber Piles

•Bakau Piles

•R.C. Square Piles

•Pre-Stressed Concrete SpunPiles

•Steel Piles

•Boredpiles

•Micropiles

•Caisson Piles

R.C. Square PilesR.C. Square Piles

Size : 150mm to 400mmLengths : 3m, 6m, 9m and 12mStructural Capacity : 25Ton to 185TonMaterial : Grade 40MPa ConcreteJoints: WeldedInstallation Method :

–Drop Hammer–Jack-In

RC RC Square Square PilesPiles

Pile MarkingPile Marking

Pile LiftingPile Lifting

Pile Fitting to Piling MachinePile Fitting to Piling Machine

Pile Pile PositioningPositioning

Pile JoiningPile Joining

Considerations in Using RC Considerations in Using RC Square Piles Square Piles ……

•Pile Quality

•Pile Handling Stresses

•Driving Stresses

•Tensile Stresses

•Lateral Loads

•Jointing

PrePre--stressed Concrete Spun stressed Concrete Spun PilesPiles

Size : 250mm to 1000mmLengths : 6m, 9m and 12m (Typical)Structural Capacity : 45Ton to 520TonMaterial : Grade 60MPa & 80MPa ConcreteJoints: WeldedInstallation Method :

–Drop Hammer–Jack-In

Spun PilesSpun Piles

Spun Piles Spun Piles vsvs RC Square Piles RC Square Piles Spun Piles have …

•Better Bending Resistance

•Higher Axial Capacity

•Better Manufacturing Quality

•Able to Sustain Higher Driving Stresses

•Higher Tensile Capacity

•Easier to Check Integrity of Pile

•Similar cost as RC Square Piles

Steel H PilesSteel H Piles

Size : 200mm to 400mLengths : 6m and 12mStructural Capacity : 40Ton to 1,000TonMaterial : 250N/mm2 to 410N/mm2 SteelJoints: WeldedInstallation Method :

–Hydraulic Hammer–Jack-In

Steel H Steel H PilesPiles

Steel H Piles (ContSteel H Piles (Cont’’d)d)

Steel H Piles NotesSteel H Piles Notes……

•Corrosion Rate

•Fatigue

•OverDriving

OverDrivingOverDrivingof Steel Pilesof Steel Piles

Large Diameter CastLarge Diameter Cast--InIn--Situ Situ Piles (Bored Piles)Piles (Bored Piles)

Size : 450mm to 2m (Up to 3.0m for special case)Lengths : VariesStructural Capacity : 80Ton to 2,300TonsConcrete Grade : 20MPa to 35MPa (Tremie)Joints : NoneInstallation Method : Drill then Cast-In-Situ


Bedrock

Drilling BorepileBorepile ConstructionConstruction


Bedrock

Advance Drilling BorepileBorepile ConstructionConstruction


Bedrock

Drilling & Advance Casing

BorepileBorepile ConstructionConstruction


Bedrock

Drill to Bedrock BorepileBorepile ConstructionConstruction



Bedrock

Lower Reinforcement Cage


Bedrock

BorepileBorepile ConstructionConstructionLower TremieChute


Bedrock

Pour TremieConcrete




Bedrock

Completed Borepile

BORED PILING MACHINEBORED PILING MACHINEBored Pile Construction

BG22

Cleaning Bucket

Rock Reamer Rock Auger

Harden Steel

Rock Chisel

DRILLING EQUIPMENTDRILLING EQUIPMENTBored Pile Construction

Soil augerCoring bucketCleaning

bucket

BENTONITE PLANTBENTONITE PLANTBored Pile Construction

MixerWater Tank Slurry

Tank

DesandingMachine

DrillingDrilling

Lower Lower ReinforcementReinforcement

Place Place TremieTremie

ConcreteConcrete

Completed Completed BoredpileBoredpile

BorepileBorepile CosiderationsCosiderations……

•Borepile Base Difficult to Clean

•Bulging / Necking

•Collapse of Sidewall

•Dispute on Level of Weathered Rock

MicropilesMicropiles

Size : 100mm to 350mm DiameterLengths : VariesStructural Capacity : 20Ton to 250TonMaterial : Grade 25MPa to 35MPa Grout

N80 API Pipe as ReinforcementJoints: NoneInstallation Method :

–Drill then Cast-In-Situ–Percussion Then Cast-In-Situ

CastCast--InIn--Situ Situ PilesPiles

((MicropilesMicropiles))

TYPES OF PILE SHOESTYPES OF PILE SHOES

•Flat Ended Shoe

•Oslo Point

•Cast-Iron Pointed Tip

•Cross Fin Shoe

•H-Section

Cross Fin ShoeCross Fin Shoe

Do more harm in inclined rock surface!

Oslo Point ShoeOslo Point Shoe

Cast Iron Tip ShoeCast Iron Tip Shoe


HH--Section ShoeSection Shoe


Piling Supervision

Uniform Building By Uniform Building By Law (UBBL)1984Law (UBBL)1984

PILING SUPERVISIONPILING SUPERVISION•Ensure That Piles Are Stacked Properly

•Ensure that Piles are Vertical During Driving

•Keep Proper Piling Records

•Ensure Correct Pile Types and Sizes are Used

•Ensure that Pile Joints are Properly Welded withNO GAPS

•Ensure Use of Correct Hammer Weights and DropHeights

PILING SUPERVISION PILING SUPERVISION (Cont(Cont’’d)d)

•Ensure that Proper Types of Pile Shoes are Used.

•Check Pile Quality

•Ensure that the Piles are Driven to the RequiredLengths

•Monitor Pile Driving

FAILURE OF PILING FAILURE OF PILING SUPERVISIONSUPERVISION

Failing to Provide Proper Supervision

WILL Result in

Higher Instances of Pile Damage

& Wastage

Pile Damage

Driven concrete piles are vulnerable Driven concrete piles are vulnerable to damages by overdriving. to damages by overdriving.

Damage to Timber PileDamage to Timber Pile

Weak Weak Timber Timber JointJoint

Damage To RC Pile ToeDamage To RC Pile Toe

Damage to Damage to RC Pile RC Pile HeadHead

Damage to Damage to RC PilesRC Piles

Damage to RC Piles Damage to RC Piles –– contcont’’d d

Tilted RC Tilted RC PilesPiles

Damage to Steel PilesDamage to Steel Piles

Damaged Steel Pipe PilesDamaged Steel Pipe Piles

Detection of Pile Damage Detection of Pile Damage Through Piling RecordsThrough Piling Records

Piling Problems

Piling Problems – Soft Ground

Ground heave due to pressure relief at base &

surcharge near excavation

Pile tilts & moves/walks



Piling in Kuala Lumpur LimestonePiling in Kuala Lumpur Limestone

Important Points to Note:• Highly Irregular Bedrock Profile

• Presence of Cavities & Solution Channels

• Very Soft Soil Immediately Above Limestone Bedrock

Results in …• High Rates of Pile Damage

• High Bending Stresses

Piling Problems in Typical Limestone Piling Problems in Typical Limestone BedrockBedrock

Piling Problems Piling Problems –– Undetected Undetected ProblemsProblems

Piling Problems Piling Problems – Coastal Alluvium

Piling Problems Piling Problems –– Defective PilesDefective Piles

Seriously damaged pile due to severe driving stress in soft ground (tension)

Defect due to poor workmanship of pile casting

Defective pile shoe

Problems of defective pile head & overdriving!


Cracks& fractured

Non-chamfered corners


Pile head defect due to hard driving or and poor

workmanship


Piling Problem - Micropiles

Sinkholes caused by installation method-

dewatering?

Piling in Fill GroundPiling in Fill GroundImportant Points to Note:

•High Consolidation Settlements If Original Ground is Soft•Uneven Settlement Due to Uneven Fill Thickness•Collapse Settlement of Fill Layer If Not Compacted Properly

Results in …•Negative Skin Friction (NSF) & Crushing of Pile Dueto High Compressive Stresses

•Uneven Settlements

Typical Design and Typical Design and Construction Issues #1Construction Issues #1

Pile Toe Slippage Due to Steep Incline Bedrock

Use Oslo Point Shoe To Minimize Pile Damage

Issue #1

Solution #1

Pile Breakage on Inclined Pile Breakage on Inclined Rock SurfaceRock Surface

No Proper Pile Shoe

Extension PilePileJoint

First Contact B/W Toe and Inclined Rock

Toe “Kicked Off”on Driving

Pile Body Bends

Pile Joint Breaks

Pile Breakage on Inclined Pile Breakage on Inclined Rock SurfaceRock Surface

Continue “Sliding” of

Toe

Use Oslo Point Shoe to Minimize Use Oslo Point Shoe to Minimize DamageDamage

Design and Construction Design and Construction Issues #2Issues #2

Presence of Cavity

Detect Cavities through Cavity Probing then perform Compaction Grouting

Issue #2

Solution #2

Presence of CavityPresence of Cavity

Pile Sitting on Limestone with Cavity

Application of Building Load

Application of Building Load

Roof of Cavity starts to Crack …

Collapse of Cavity Roof

Pile Plunges !

Building Collapse

Design and Construction Design and Construction Issues #3Issues #3

Differential Settlement

Carry out analyses to check the settlement compatibility if different piling system is adopted

Issue #3

Solution #3

Piling in Progress

Differential Settlement of Foundation

Original House on Piles

Hard LayerSPT>50

Cracks!!

No pile

SettlementSoft

Layer

Link House Construction

Renovation: Construct

Extensions

Piles transfer Load to

Hard Layer

No Settlement

SAFETY of Original Building

Not Compromised

Piling in Progress

Eliminate Differential SettlementEliminate Differential Settlement

Hard LayerSPT>50

Soft Layer

Construct Extension with Suitable Piles

All Load transferred to Hard Layer – No Cracks!

Piling in Progress

Problem of Short PilesProblem of Short Piles

Hard LayerSPT>50

Soft Layer

Load from Original House transferred to Hard Layer

Cracks!!

Soft!

Load transferred to

Soft Layer, Extension still Settles

Construct Extensions with Short

Piles

Cracks at ExtensionCracks at Extension


Costly conventional piling design – piled to set to deep layer in soft ground

-Strip footings / Raft

-Floating Piles

Issue #4

Solution #4

“Conventional” Foundation for Low Rise Buildings

Foundation for Low Rise Buildings (Soil Settlement)

Exposed Pile

Settlement


Conceptual Design of Conceptual Design of FOUNDATION SYSTEMFOUNDATION SYSTEM

1. Low Rise Buildings :-(Double-Storey Houses)= Strip Footings or Raft or Combination.

2. Medium Rise Buildings :-= Floating Piles System.

Low Rise Buildings on Piled Raft/Strips

Strip / Raft System

Stiff Stratum

Hard Layer

Fill

25-30m

Soft Clay

Comparison

Strip System

Stiff Stratum

Hard Layer

Fill

25-30m

Soft Clay

Building on Piles Building on Piled Strips

Comparison (after settlement)Building on Piles Building on Piled Strips

Strip System

Stiff Stratum

Hard Layer

Fill

25-30m

Soft Clay

Advantages of Advantages of Floating Piles SystemFloating Piles System

1. Cost Effective.

2. No Downdrag problems on the Piles.

3. Insignificant Differential Settlement between Buildings and Platform.

Bandar Botanic

Bandar Botanic at Night


Load test results far below predicted pile capacity

-Modifications to test set-up

-Change of pile installation method

-Adequate soil plug to prevent toe softening

Issue #5

Solution #5

Testing SetTesting Set--up Using Reaction up Using Reaction PilesPiles

Testing SetTesting Set--up up

Long reaction piles at close spacing used

Case histories:– Load tests using reaction piles give

ERRATIC results– Reference: Weele (1993)

≈ 1100kN

Tested using

anchor piles

≈ 2100kN

Tested using

kentledge

Approx. 2 times

smaller using

reaction piles!

Ref: A.F. van Weele, 1993

Reaction piles

Test pile

Zone of interaction

with test pile

Testing SetTesting Set--up up

Latest version of ASTM D1143Published April 2007

Testing SetTesting Set--upup

ASTM D1143– Clear distance of at least 5 times

the maximum diameter– Caution on factors influencing

results:“Possible interaction ……….from anchor piles……..”

Drilling to the Casing Tip Drilling to the Casing Tip to Form to Form ““Bored PileBored Pile””

Drilling to Form Drilling to Form ““Bored PileBored Pile””

Disturbance to soil at tip and surrounding the pile

Potential hydraulic/basal heave failure resulting in lower soil strength

Effect more severe for longer pile

Construction of Construction of ““Bored PileBored Pile””1. Install Permanent Steel

Casing to Pile Toe

2. Removal of Soil within Steel Casing to Toe of Casing

3. Installation of Reinforcement and Concreting

Drilling to Form Drilling to Form ““Bored PileBored Pile””

Pile behaviour COMPLICATED!

– Influenced by steel casing which behave like DRIVEN PILE

– Influenced by soil removal which behave like BORED PILE

SAND UPHEAVAL

AFTER 3 HRS

Zone of Weakened Soil due to Installation of Steel Casing using Vibro-hammer

Pressure from

Drilling Fluid

Pressure from Soil + Water

Pressure from Soil + Water > Pressure from

Drilling Fluid

Further Soil Disturbance –Magnitude of Disturbance?????

Probable causes of erratic and unpredictable pile capacities:

– Testing set-up using reaction piles– Drilling to the casing tip to form “bored pile”

Original Load TestOriginal Load Test– 1st Load Test – Failed at 90% of WL

After 32 days

– 2nd Load Test – Failed at 110% of WLAfter 94 days

Recommendations:

– Open-ended spun pile or steel pipe pile with adequate soil plug

– Use of impact hammer instead of vibro-hammer

– Trial piles for correlation between static load test and high strain dynamic load test

Result for Concreted

Pile

Result for Empty Casing

Pile performs satisfactorily

within acceptable settlement limits!!!

Settlement at 1WL = 12.5mm

Load Test Results at P52WLoad Test Results at P52W– Result for Empty Casing

1xWL: pile settlement= 20mm(residual settlement= 1mm)1.9xWL: pile settlement= 50mm(residual settlement= 3mm)

– Result for Cast Pile1xWL: pile settlement= 12.5mm(residual settlement= 1mm)2xWL: pile settlement= 33.4mm(residual settlement= 7mm)

The Pile is Stiffer after

Concreting !!

Larger Residual Settlement due to Disturbance from

RCD work !!

Load Test Results at P52WLoad Test Results at P52W

– Research by Ng et al., 2001:Elastic compression of large diameter bored piles:–½ PL/AE - Piles founded in soil–¾ PL/AE - Piles founded in rocks

Result for Concreted Pile

Piles founded in SOIL: ½ PL/AE

Piles founded in ROCK: 3/4 PL/AE

Settlement is in

accordance to

prediction!!

Depends on:– E – Elastic Modulus of Pile Material– A – Cross-sectional Area of Pile– L – Pile Length

Elastic Compression = f (PL / AE)

Therefore, after concreting of pile:- A increased significantly (composite E due to

steel and concrete reduced slightly)- Elastic compression will reduce

ELASTIC COMPRESSION OF PILEELASTIC COMPRESSION OF PILE

Pile Settlement CriteriaPile Settlement Criteria

Pile settlement criteria depends on– Pile Size– Pile Material (e.g. steel, concrete, etc.)– Pile Length

Unrealistic to adopt same settlement criteria (e.g. 12mm) for all piles (regardless of length, size, etc.)

Myths in Piling

MYTHS IN PILING #1MYTHS IN PILING #1

Dynamic Formulae such as Hiley’s Formula Tells us the Capacity of the Pile

Pile Capacity can only be verified by using:

(i) Maintained (Static) Load Tests

(ii)Pile Dynamic Analyser (PDA) Tests

Myth:

Truth:


Pile Achieves Capacity When It is Set.

Myth:

Truth:

Pile May Only “Set” on Intermediate Hard Layer BUT May Still Not Achieve Required Capacity within Allowable Settlement.


Pile settlement at 2 times working load must be less than certain magnitude (e.g. 38mm)

Myth:

Truth:

Pile designed to Factor of Safety of 2.0. Therefore, at 2 times working load:

Pile expected to fail unless capacity under-predicted significantly


GlobalGlobal factor of safety for total ultimate factor of safety for total ultimate capacitycapacity

Use 2.0 (typical)Use 2.0 (typical)

ΣQsu + Qbu

2.0Qall =


Jack-in piles cannot be used for high-rise buildings or in limestone formation

Myth:

Truth:

Jack-in piles can be used for high-rise buildings and limestone formation

- With proper design and input from experienced geotechnical engineer


Site A

31-storey


Site B 45-storey


Site C

Target Completion Mid 2011

40 to 43-storey

ADVANCES IN FOUNDATION ADVANCES IN FOUNDATION DESIGNDESIGNPILED RAFT FOUNDATION

PILED RAFT FOUNDATIONPILED RAFT FOUNDATION

Using conventional approach where part of the superstructure load is transferred to the slab/pilecap in contact with the ground

At least 25% to 40% reduction of numbers of piles – depending on soil conditions

PILED RAFT FOUNDATIONPILED RAFT FOUNDATIONSettlement reducing piles/full piled raft

Piles introduced to control settlement

Piles required may be as little as 10% of conventional pile design

Refer to publications by Randolph, Poulos, Katzenbach, etc.

CASE HISTORIESCASE HISTORIES

MEDIUM RISE BUILDINGSMEDIUM RISE BUILDINGS

200mm x 200mm reinforced concrete (RC) square piles with pile length varying from 18m to 24m:

350mm x 700mm strips and 300mm thick raft

Foundation Design for

5-Storey Low Cost

Apartment

CSM01

CSM02

CSM03

CSM04

CSM05

CSM06

CSM07

CSM08

CSM09

CSM10

CSM11

CSM12

CSM13

CSM14

Legend:CSM – Settlement markers (14 Nos.)

Total of 14 numbers of precise settlement markersMonitored results up to 313 days

SETTLEMENT MONITORING

CSM02

-33.55 -13.9 13.9 33.55Distance (m)

807978777675747372717069686766656463626160

Set

tlem

ent (

mm

)

-33.55 -13.9 13.9 33.55

807978777675747372717069686766656463626160

CSM05

CSM10

CSM14Centreline

β = 1/2356

β = 1/17595

β = 1/1698

β = 1/13950

Settlement Profile Across Edge of Building

Maximum differential settlement: 27mmMaximum local angular distortion: 1/1215

COMPLETED APARTMENTCOMPLETED APARTMENT

2500 Ton Siloon Very Soft Marine Deposits

Foundations for Foundations for HighriseHighrise

Bistari Condominiums, KL.Alternative design has reduced the foundation cost by more than 50%, A saving of more than RM5 million. An Award of Merit (1998) was given by ACEM.

Fill / Alluvium

Concrete Raft

SUMMARYSUMMARY

Importance of Preliminary Study

Understanding the Site Geology

Carry out Proper Subsurface Investigation that Suits the Terrain & Subsoil

Selection of Suitable Pile

Pile Design Concepts

SUMMARYSUMMARY

Importance of Piling Supervision

Typical Piling Problems Encountered

Present Some Case Histories

FERRARI ‘S PITSTOP WAS COMPLETED BY 15 MECHANICS (FUEL AND TYRES) IN 6.0 SECONDS FLAT.

54 PEOPLE TOOK PART IN THIS CONCERTED ACROBATIC JUMP.

CONTENTSgnpgeo.com.my/download/publication/L2013_02.pdf · 2018-07-25 · • Advanced static cone...

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