PILED FOUNDATION DESIGN & CONSTRUCTION

Transcription

1 PILED FOUNDATION DESIGN & CONSTRUCTION By Ir. Dr. Gue See Sew

2 Contents Overview Preliminary Study Site Visit & SI Planning Pile Design Pile Installation Methods Types of Piles

3 Contents (Cont d) Piling Supervision Pile Damage Piling Problems Typical Design and Construction Issues Myths in Piling Case Histories Conclusions

4 Overview

5 What is a Pile Foundation It is a foundation system that transfers loads to a deeper and competent soil layer.

6 When To Use Pile Foundations Inadequate Bearing Capacity of Shallow Foundations To Prevent Uplift Forces To Reduce Excessive Settlement

7

8 PILE CLASSIFICATION Friction Pile Load Bearing Resistance derived mainly from skin friction End Bearing Pile Load Bearing Resistance derived mainly from base

9 Overburden Soil Layer Friction Pile

10 End Bearing Pile Overburden Soil Rock / Hard Layer

11 Preliminary Study

12 Preliminary 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

13 Previous Data & Case Histories Existing Development A Proposed Development Existing Development B Only Need Minimal Number of Boreholes Bedrock Profile

14 Challenge The Norm Thru Innovation To Excel

15 SELECTION 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

16 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 Hollow Small displacement Solid Concrete Tube Steel Tube Steel Pipe Concrete Spun Piles Closed ended tube concreted with tube left in position Closed ended tube Open ended tube extracted while concreting (Franki) Concrete Steel H-piles (small displacement) Bakau piles Treated timber pile Precast R.C. piles Precast prestressed piles FIG 1: CLASSIFICATION OF PILES

17 PREFORMED PILES LEGEND : GEOTECHNICAL SCALE OF LOAD (STRUCTURAL) BEARING TYPE TYPE OF BEARING LAYER GROUND WATER UNIT COST TYPE OF INTERMEDIATE LAYER ENVIRONME NT DESIGN CONSIDERATIONS TYPE OF PILE BAKAU PILES <100 KN a a a???? a x? a a a a?? a a a x a a ? a a a a a a a a a a COMPRESSIVE LOAD PER COLUMN x? a a a a a? a a? x? a a a a a? a a? x x a a a a a? a a? 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 MAINLY END -BEARING 10-20m?? (D=Anticipated depth of bearing) 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 MAINLY FRICTION a a a a a? a a a? a PARTLY FRICTION + PARTLY END BEARING a a a a a a a a a? a LIMESTON FORMATION????? a a a? a a WEATHERED ROCK / SOFT ROCK x x a a a a a? a a? ROCK (RQD > 70%) x x??? a a? a a? DENSE / VERY DENSE SAND x? a a a a a a a a a SOFT SPT < 4 a a a a a a a a a? a COHESIVE SOIL M. STIFF SPT = 4-15 a a a a a a a a a a a V. STIFF SPT = 15-32? a a a a a a a a a a HARD SPT > 32 x? a a a a a a a a a LOOSE SPT < 10 a a a a a a a a a a a COHESIVELESS SOIL M. DENSE SPT = 10-30? a a a a a a a a a a DENSE SPT = 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? SOIL WITH SOME BOULDERS / mm x x??? a a? a a x COBBLES (S=SIZE) mm x x??????? a x >3000mm x x??????? a x ABOVE PILE CAP a a a a a a a a a a a BELOW PILE CAP x a a a a a a a a a a NOISE + VIBRATION; COUNTER MEASURES REQUIRED a a????? a a a a PREVENTION OF EFFECTS ON ADJOINING STRUCTURES??????? a? a a (SUPPLY & INSTALL) RM/TON/M TIMPER PILES RC PILES PSC PILES SPUN PILES STEEL H PILES STEEL PIPE PILES JACKED PILES BORED PILES MICROPILES AUGERED PILES 8 x? INDICATES THAT THE PILE TYPE IS SUITABLE INDICATES 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

18 Pile Selection Based on Cost Details: 250mm Spun Piles 300mm Spun Piles Micropile Total Points Average Length 9m 9m 9m Average Rock Socket Length m Indicative Rates : Mob & Demob RM 50, RM 50, RM 20, Supply RM / m RM / m - Drive RM / m RM / m - Cut Excess, Dispose + Starter Bars RM / Nos RM / Nos - Movement - - RM / Nos Drilling in Soil - - RM / m Drilling in Rock - - RM / m API Pipe - - RM / m Grouting - - RM / m Pile Head - - RM / Nos Est. Ave. Cost Per Point RM / Nos RM 1, / Nos RM 4, / Nos Est. Foundation Cost RM 190, RM 184, RM 380,825.00

19 Site Visit and SI Planning

20 Site Visit Things 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

21 Subsurface Investigation (SI) Planning 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)

22 Typical Cross-Section at Hill Site Hard Material Level Ground Level Very Hard Material Level Bedrock Level Groundwater Level

23 CROSS SECTION BH EXISTING GROUND LEVEL BH C 1, ø 1 BH Perched WT Clayey Layer C 2, ø 2 Seepage C 3, ø 3 Water Table

24 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

25 Pile Design

26 PILE DESIGN Allowable Pile Capacity is the minimum of : 1) Allowable Structural Capacity 2) Allowable Geotechnical Capacity a. Negative Skin Friction b. Settlement Control

27 PILE DESIGN Structural 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 Durability assessment

28 Pile Capacity Design Structural Capacity Concrete Pile Q all = 0.25 x f cu x A c Steel Pile Q all = 0.3 x f y x A s Q all = Allowable pile capacity f cu = characteristic strength of concrete f s = yield strength of steel A c = cross sectional area of concrete A s = cross sectional area of steel Prestressed Concrete Pile Q all = 0.25 (f( cu Prestress after loss) x A c

29 Pile Capacity Design Geotechnical Capacity Collection of SI Data Depth (m) Depth Vs SPT-N Blow Count Upper Bound Lower Bound Design Line (Moderately Conservative) SPT Blow Count per 300mm Penetration

30 Pile Capacity Design Geotechnical Capacity Collection of SI Data Depth Vs SPT-N Blow Count Depth Vs SPT-N Blow Count Depth (m) Upper Bound 4 6 Depth (m) Lower Bound Design Line Lower Bound Design Line Upper Bound SPT Blow Count per 300mm Penetration SPT Blow Count per 300mm Penetration

31 Pile Capacity Design Geotechnical Capacity Piles installed in a group may fail: Individually As a block

32 Pile Capacity Design Geotechnical Capacity Piles fail individually When installed at large spacing

33 Pile Capacity Design Geotechnical Capacity Piles fail as a block When installed at close spacing

34 Pile Capacity Design Single Pile Capacity

35 Pile Capacity Design Factor of Safety (FOS) Factor of Safety (FOS) is required for Natural variations in soil strength & compressibility

36 Pile Capacity Design Factor of Safety (FOS) Factor of Safety is (FOS) required for Different degree of mobilisation for shaft & for tip Load q smob q bmob 5mm Settlement

37 Pile Capacity Design Factor of Safety (FOS) Partial factors of safety for shaft & base capacities respectively For shaft, use 1.5 (typical) For base, use 3.0 (typical) Q ΣQ su + Q bu all =

38 Pile Capacity Design Factor of Safety (FOS) Global factor of safety for total ultimate capacity Use 2.0 (typical) Q all = ΣQ su + Q bu 2.0

39 Pile Capacity Design Factor of Safety (FOS) Calculate using BOTH approaches (Partial & Global) Choose the lower of the Q all values

40 Pile Capacity Design Single Pile Capacity Q u = Q s + Q b Q u = ultimate bearing capacity Q s = skin friction Q b = end bearing Overburden Soil Layer

41 Pile Capacity Design Single Pile Capacity : In Cohesive Soil Q su Q bu Q u = α.s us.a s + s ub.n c.a b Q u = Ultimate bearing capacity of the pile a = adhesion factor (see next slide) s us = average undrained shear strength for shaft A s = surface area of shaft s ub = undrained shear strength at pile base N c = bearing capacity factor (taken as 9.0) A b = cross sectional area of pile base

42 Pile Capacity Design Single Pile Capacity: In Cohesive Soil Adhesion factor (α)( Shear strength (S u ) (McClelland, 1974) Preferred Design Line 0.6 C α /S u 0.4 Adhesion Factor Su (kn/m 2 )

43 Meyerhof Fukuoka SPT N f su =2.5N (kpa) s u = ( N)*50 (kpa) α f su =α.s u (kpa)

44 Pile Capacity Design Single Pile Capacity: In Cohesive Soil Correlation Between SPT N and f su f su vs SPT N fsu (kpa) SPT N Meyerhof Fukuoka

45 Pile Capacity Design Single Pile Capacity: In Cohesive Soil Values of undrained shear strength, s u can be obtained from the following: Unconfined compressive test Field vane shear test Deduce based on Fukuoka s Plot (minimum s u ) Deduce from SPT-N values based on Meyerhof NOTE: Use only direct field data for shaft friction prediction instead of Meyerhof

46 Pile Capacity Design Single Pile Capacity: In Cohesive Soil Modified Meyerhof (1976): Ult. Shaft friction = Q su 2.5N (kpa) Ult. Toe capacity = Q bu 250N (kpa) or 9 s u (kpa) (Beware of base cleaning for bored piles ignore base capacity if doubtful)

47 Pile Capacity Design Single Pile Capacity: In Cohesionless Soil Modified Meyerhof (1976): Ult.. Shaft Friction = Q su 2.0N (kpa( kpa) Ult.. Toe Capacity= Q bu 250N 400N (kpa)

48 Pile Capacity Design Load (kn) ΣQ su Depth (m) 8 12 ΣQ su + Q bu Q bu ΣQ su + Q bu ΣQ su + Q bu

49 Pile Capacity Design Block Capacity

50 Pile Capacity Design Block Capacity:In Cohesive Soil Q u = 2D(B+L) s + 1.3(s b.n c.b.l) Where Q u = ultimate bearing capacity of pile group D = depth of pile below pile cap level B = width of pile group L = length of pile group s = average cohesion of clay around group s b = cohesion of clay beneath group N c = bearing capacity factor = 9.0 (Refer to Text by Tomlinson, 1995)

51 Pile Capacity Design Block Capacity: In Cohesionless Soil No risk of group failure if FOS of individual pile is adequate

52 Pile Capacity Design Block Capacity: On Rock No risk of block failure if the piles are properly seated in the rock formation

53 Pile Capacity Design Negative Skin Friction (NSF)

54 Pile Capacity Design Negative Skin Friction Compressible soil layer consolidates with time due to: Surcharge of fill Lowering of groundwater table

55 Pile Capacity Design Negative Skin Friction OGL Fill H f ρ s Month Clay

56 Pile Capacity Design Negative Skin Friction Pile to length (floating pile) Pile settles with consolidating soil NO NSF

57 Pile Capacity Design Negative Skin Friction Pile to set at hard stratum (endbearing pile) Consolidation causes downdrag forces on piles as soil settles more than the pile

58 Pile Capacity Design Negative Skin Friction WARNING: No free fill by the contractor to avoid NSF

59 Effect of NSF Reduction of Pile Carrying Capacity

60 Effect of NSF

61 NSF Preventive Measures Avoid Filling Carry Out Surcharging Sleeve the Pile Shaft Slip Coating Reserve Structural Capacity for NSF Allow for Larger Settlements

62 Pile Capacity Design Negative Skin Friction Q all = (Q su /1.5 + Q bu /3.0) Q all = (Q su /1.5 + Q bu /3.0) - Q neg OGL Sand FL OGL Clay Q su Clay Q neg Sand Sand Q su Q ba Q ba

63 0 Pile Capacity Design Negative Skin Friction Increased Pile Axial Load Check: maximum axial load < structural pile SPT-N (Blows/300mm) Settlement (mm) capacity Axial Compression Force (kn) Depth (m, bgl) Borehole BH-1 BH-2 Settlement Curves & Axial Compression Force 14 May May May May Jun Jun Jun Jul Jul 98 Datum = m Maximum axial load

64 Pile Capacity Design Factor of Safety (FOS) Without Negative Skin Friction: Allowable working load Q ult FOS With Negative Skin Friction: Allowable working load Q ult FOS (Q neg + etc)

65 Pile Capacity Design Static Pile Load Test (Piles with NSF) Specified Working Load (SWL) = Specified foundation load at pile head Design Verification Load (DVL) = SWL + 2 Q neg Proof Load: will not normally exceed DVL + SWL

66 Pile Settlement Design

67 Pile Settlement Design In Cohesive Soil Design for total settlement & differential settlement for design tolerance In certain cases, total settlement not an issue Differential settlement can cause damage to structures

68 Pile Settlement Design In Cohesive Soil Pile Group Settlement in Clay = Immediate / Elastic Settlement + Consolidation Settlement

69 IMMEDIATE SETTLEMENT μ μ0q p = 1 i E Where p i = average immediate settlement q n= pressure at base of equivalent raft B = width of the equivalent raft E u = deformation modulus Pile Settlement Design In Cohesive Soil u n B μ 1, μ 0 = influence factors for pile group width, B at depth D below ground surface by Janbu, Bjerrum and Kjaernsli (1956)

70 IMMEDIATE SETTLEMENT Pile Settlement Design In Cohesive Soil μ 1 μ 0 Influence factors (after Janbu, Bjerrum and Kjaernsli, 1956)

71 Pile Settlement Design In Cohesive Soil CONSOLIDATION SETTLEMENT As per footing (references given later)

72 Pile Settlement Design On Rock No risk of excessive settlement

73 Pile Installation Methods

74 PILE INSTALLATION METHODS Diesel / Hydraulic / Drop Hammer Driving Jacked-In Prebore Then Drive Prebore Then Jacked In Cast-In-Situ Pile

75 Diesel Drop Hammer Driving Hydraulic Hammer Driving

76 Jacked-In Piling

77 Jacked-In Piling (Cont d)

78 Cast-In-Situ Piles (Micropiles)

79 Types of Piles

80 TYPES OF PILES Treated Timber Piles Bakau Piles R.C. Square Piles Pre-Stressed Concrete Spun Piles Steel Piles Boredpiles Micropiles Caisson Piles

81 R.C. Square Piles Size : 150mm to 400mm Lengths : 3m, 6m, 9m and 12m Structural Capacity : 25Ton to 185Ton Material : Grade 40MPa Concrete Joints: Welded Installation Method : Drop Hammer Jack-In

82 RC Square Piles

83 Pile Marking

84 Pile Lifting

85 Pile Fitting to Piling Machine

86 Pile Positioning

87 Pile Joining

88 Considerations in Using RC Square Piles Pile Quality Pile Handling Stresses Driving Stresses Tensile Stresses Lateral Loads Jointing

89 Pre-stressed Concrete Spun Piles Size : 250mm to 1000mm Lengths : 6m, 9m and 12m (Typical) Structural Capacity : 45Ton to 520Ton Material : Grade 60MPa & 80MPa Concrete Joints: Welded Installation Method : Drop Hammer Jack-In

90 Spun Piles

91 Spun Piles vs 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

92 Steel H Piles Size : 200mm to 400m Lengths : 6m and 12m Structural Capacity : 40Ton to 1,000Ton Material : 250N/mm 2 to 410N/mm 2 Steel Joints: Welded Installation Method : Hydraulic Hammer Jack-In

93 Steel H Piles

94 Steel H Piles (Cont d)

95 Steel H Piles Notes Corrosion Rate Fatigue OverDriving

96 OverDriving of Steel Piles

97 Large Diameter Cast-In In-Situ Piles (Bored Piles) Size : 450mm to 2m Lengths : Varies Structural Capacity : 80Ton to 2,300Tons Concrete Grade : 20MPa to 30MPa (Tremie) Joints : None Installation Method : Drill then Cast-In-Situ

98 Drilling Borepile Construction Overburden Soil Layer Bedrock

99 Advance Drilling Borepile Construction Overburden Soil Layer Bedrock

100 Drilling & Advance Casing Borepile Construction Overburden Soil Layer Bedrock

101 Drill to Bedrock Borepile Construction Overburden Soil Layer Bedrock

102 Lower Reinforcement Cage Borepile Construction Overburden Soil Layer Bedrock

103 Lower Tremie Chute Borepile Construction Overburden Soil Layer Bedrock

104 Pour Tremie Concrete Borepile Construction Overburden Soil Layer Bedrock

105 Completed Borepile Borepile Construction Overburden Soil Layer Bedrock

106 BORED PILING MACHINE Bored Pile Construction BG22

107 Cleaning Bucket Rock Reamer Rock Auger

108 Rock Chisel Harden Steel

109 DRILLING EQUIPMENT Bored Pile Construction Cleaning bucket Coring bucket Soil auger

110 Bored Pile Construction BENTONITE PLANT Desanding Machine Water Tank Mixer Slurry Tank

111 Drilling

112 Lower Reinforcement

113 Place Tremie Concrete

114 Completed Boredpile

115 Borepile Cosiderations Borepile Base Difficult to Clean Bulging / Necking Collapse of Sidewall Dispute on Level of Weathered Rock

116 Micropiles Size : 100mm to 350mm Diameter Lengths : Varies Structural Capacity : 20Ton to 250Ton Material : Grade 25MPa to 35MPa Grout Joints: None Installation Method : N80 API Pipe as Reinforcement Drill then Cast-In-Situ Percussion Then Cast-In-Situ

117 Cast-In In-Situ Piles (Micropiles)

118 TYPES OF PILE SHOES Flat Ended Shoe Oslo Point Cast-Iron Pointed Tip Cross Fin Shoe H-Section

119 Cross Fin Shoe

120 Oslo Point Shoe

121 Cast Iron Tip Shoe

122 H-Section Shoe

123 Piling Supervision

124 Uniform Building By Law (UBBL)1984

125 PILING 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 with NO GAPS Ensure Use of Correct Hammer Weights and Drop Heights

126 PILING SUPERVISION (Cont d) Ensure that Proper Types of Pile Shoes are Used. Check Pile Quality Ensure that the Piles are Driven to the Required Lengths Monitor Pile Driving

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129 FAILURE OF PILING SUPERVISION Failing to Provide Proper Supervision WILL Result in Higher Instances of Pile Damage & Wastage

130 Pile Damage

131 Driven concrete piles are vulnerable to damages by overdriving.

132 Damage to Timber Pile

133 Weak Timber Joint

134 Damage To RC Pile Toe

135 Damage to RC Pile Head

136 Damage to RC Piles

137 Damage to RC Piles cont d

138 Tilted RC Piles

139 Damage to Steel Piles

140 Damaged Steel Pipe Piles

141

142 Detection of Pile Damage Through Piling Records

143 Piling Problems

144 Piling Problems Soft Ground

145 Piling Problems Soft Ground Ground heave due to pressure relief at base & surcharge near excavation Pile tilts & moves/walks

146 Piling Problems Soft Ground

147 Piling 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

148 Piling Problems in Typical Limestone Bedrock

149 Piling Problems Undetected Problems

150 Piling Problems Coastal Alluvium

151 Piling Problems Defective Piles Seriously damaged pile due to severe driving stress in soft ground (tension) Defect due to poor workmanship of pile casting

152 Piling Problems Defective Piles Defective pile shoe Problems of defective pile head & overdriving!

153 Piling Problems Defective Piles Nonchamfered corners Cracks& fractured

154 Piling Problems Defective Piles Pile head defect due to hard driving or and poor workmanship

155 Piling Problem - Micropiles Sinkholes caused by installation methoddewatering?

156 Piling in Fill Ground Important 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 Due to High Compressive Stresses Uneven Settlements

157 Typical Design and Construction Issues #1 Issue #1 Pile Toe Slippage Due to Steep Incline Bedrock Solution #1 Use Oslo Point Shoe To Minimize Pile Damage

158 Pile Breakage on Inclined Rock Surface No Proper Pile Shoe

159 Pile Joint Extension Pile

160 First Contact B/W Toe and Inclined Rock

161 Pile Joint Breaks Pile Body Bends Toe Kicked Off on Driving

162 Pile Breakage on Inclined Rock Surface Continue Sliding of Toe

163 Use Oslo Point Shoe to Minimize Damage

164 Design and Construction Issues #2 Issue #2 Presence of Cavity Solution #2 Detect Cavities through Cavity Probing then perform Compaction Grouting

165 Presence of Cavity Pile Sitting on Limestone with Cavity

166 Application of Building Load

167 Application of Building Load Roof of Cavity starts to Crack

168 Building Collapse Pile Plunges! Collapse of Cavity Roof

169 Design and Construction Issues #3 Issue #3 Differential Settlement Solution #3 Carry out analyses to check the settlement compatibility if different piling system is adopted

170 Differential Settlement of Foundation Link SAFETY House of Construction Original Building Not Compromised Soft Layer Original House on Piles Piling in Progress No Settlement Piles transfer Load to Hard Layer No pile Cracks!! Renovation: Construct Extensions Settlement Hard Layer SPT>50

171 Eliminate Differential Settlement Construct Extension with Suitable Piles Piling in Progress Soft Layer All Load transferred to Hard Layer No Cracks! Hard Layer SPT>50

172 Problem of Short Piles Cracks!! Piling in Progress Construct Extensions with Short Piles Soft Layer Soft! Load transferred to Soft Layer, Extension still Settles Load from Original House transferred to Hard Layer Hard Layer SPT>50

173 Cracks at Extension

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177 Typical Design and Construction Issues #4 Issue #4 Costly conventional piling design piled to set to deep layer in soft ground Solution #4 -Strip footings / Raft -Floating Piles

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179 Conventional Foundation for Low Rise Buildings

180 Foundation for Low Rise Buildings (Soil Settlement)

181 Settling Platform Detached from Building Settlement Exposed Pile

182 Conceptual Design of FOUNDATION SYSTEM 1. Low Rise Buildings :- (Double-Storey Houses) = Strip Footings or Raft or Combination. 2. Medium Rise Buildings :- = Floating Piles System.

183 Low Rise Buildings on Piled Raft/Strips Fill 25-30m Soft Clay Strip / Raft System Stiff Stratum Hard Layer

184 Comparison Building on Piles Building on Piled Strips Fill 25-30m Soft Clay Strip System Stiff Stratum Hard Layer

185 Comparison (after settlement) Building on Piles Building on Piled Strips Fill 25-30m Soft Clay Strip System Stiff Stratum Hard Layer

186 Advantages of Floating Piles System 1. Cost Effective. 2. No Downdrag problems on the Piles. 3. Insignificant Differential Settlement between Buildings and Platform.

187 Bandar Botanic

188 Bandar Botanic at Night

189

190 Soft Ground Engineering

191 Myths in Piling

192 MYTHS IN PILING #1 Myth: Dynamic Formulae such as Hiley s Formula Tells us the Capacity of the Pile Truth: Pile Capacity can only be verified by using: (i) Maintained (Static) Load Tests (ii)pile Dynamic Analyser (PDA) Tests

193 MYTHS IN PILING #2 Myth: Pile Achieves Capacity When It is Set. Truth: Pile May Only Set on Intermediate Hard Layer BUT May Still Not Achieve Required Capacity within Allowable Settlement.

194 CASE HISTORIES Case 1: Structural distortion & distresses Case 2: Distresses at houses

195 CASE HISTORY 1 Distortion & Distresses on 40 Single/ 70 Double Storey Houses Max. 20m Bouldery Fill on Undulating Terrain Platform Settlement Short Piling Problems Downdrag on Piles

196 Distresses on Structures

197 Void

198 Reduced Level (m ) Offset 36.2m Offset 13.1m N=30 N=5 N=25? N=29??? Profile with SPT 'N'>50???? Piling Contractor A Offset 13.1m N=40 Profile with SPT 'N' 30??? Offset 13.1m? N=34 Original Ground Profile Filled ground Original Ground Hard Stratum Borehole Pile Toe Pile Toe of Additional Piles Building Platform Coordinate-X (mm)

199 80 Piling Contractor A Piling Contractor B R e d uced Level (m ) N=30 N=5 N=29? Offset 9.1m Profile with SPT 'N' 30???? N=34 N=28 N=41 Profile with SPT 'N'>50 Offset 9.1m Original Ground Profile Building Platform Filled ground Original Ground Hard Stratum Borehole Pile Toe Pile Toe of Additional Piles Coordinate-X (mm)

200

201 Prevention Measures Design: Consider downdrag in foundation design Alternative strip system Construction: Proper QA/QC Supervision

202 CASE HISTORY 2 Distresses on 12 Double Storey Houses & 42 Townhouses Filled ground: platform settlement Design problem: non-suspended floor with semi-suspended detailing Bad earthwork & layout design Short piling problem

203 Diagonal cracks due to differential settlement between columns Larger column settlement

204 Sagging Ground Floor Slab

205 SAGGING PROFILE OF NON- SUSPENDED GROUND FLOOR SLAB NON-SUSPENDED GROUND FLOOR SLAB BEFORE SETTLEMENT V e > V c ρ s V c V c < V e PILE PILECAP BUILDING PLATFORM PROFILE AFTER SETTLEMENT ρ s ACTUAL FILLED PLATFORM SETTLEMENT

206 Distorted Car Porch Roof

207 Poor Earthwork Layout Silt trap BLOCK 2 BLOCK 1 Temporary earth drain

208 Prevention Measures Planning: Proper building layout planning to suit terrain (eg. uniform fill thickness) Sufficient SI Design: Consider filled platform settlement Earthwork layout Construction: Supervision on earthwork & piling

209 SUMMARY 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

210 SUMMARY Importance of Piling Supervision Typical Piling Problems Encountered Present Some Case Histories

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212 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.

213