INTRODUCTION

DESIGN AND CONSTRUCTION OF DEEP FOUNDATIONS

Have been used since prehistoric times Wooden poles/piles to support the home near the lake in Switzerland 12,000 years ago Pile-supported huts in lagoons around the shores of lake in

R. Ayothiraman R A thi Department of Civil Engineering Indian Institute of Technology Delhi New Delhi – 110 016. E-mail: araman@civil.iitd.ac.in

Venezuela V l In early years, primarily used to bye-pass the water depth and soft soil layer even for lightly-loaded buildings Commonest Function: To transfer the load that cannot be adequately supported at shallow depths to a depth where adequate support becomes available.

FUNCTIONS OF PILES
• • • • • • • To carry the superstructure loads (both vertical and lateral) into/ through a soil stratum. To resist large uplift force and/or overturning moments To compact loose, cohesionless deposits -- a combination of pile volume displacement and driving vibrations (piles is withdrawn later) To control settlements when spread footing/mat is on a marginal soil/highly compressible soil To stiffen the soil beneath the machine foundations – to control both amplitudes and natural frequency of the system Provides additional safety factor beneath bridge abutments/piers, if scour is a potential problem Piles in offshore – load transfer thro’ water into underlying soil – partially embedded pile -- to vertical (buckling) and lateral load)

Use of piles

Effect of relation between foundation width and pile length on pressure distribution

1

End bearing pile pressure distributions in soil

Friction pile pressure distributions in soil

Pile Types

Function or Action

Composition and Material Timber piles Steel Piles Concrete piles Composite piles

Installation

Fallacy of testing the action of a single pile: under the test pile in (a) the clay is practically unloaded; under the completed structure in (b) it is heavily stressed

• End bearing piles • Friction piles • Tension piles • Compaction piles • Anchor piles • Fender piles • Sheet piles • Batter piles • Laterally loaded piles

Driven piles Cast-in-situ piles Driven and cast-insitu

PILES
TYPES OF PILES (contd.)

Displacement
Based on Pile Material Based on method of fabrication Prefabricated piles
Timber, steel Concrete

Large Displacement piles • Pre cast Concrete • Timber piles • Driven cast-in-situ • Mono tube etc.

Small Displacement piles Steel H – piles Pipe piles Box piles Screw piles

No Displacement piles

Timber piles Concrete piles Steel piles Composite piles

Cast-in-place piles
Concrete

Bored piles (cased, uncased)

2

TYPES OF PILES (contd.) Based on method of installation Driven piles
Timber, steel (H/pipe) Precast concrete

TYPES OF PILES (contd.) Based on load transfer mechanism

Based on amount ground disturbance Displacement piles
Large-displacement Small-displacement Ex: Driven piles

End bearing piles Friction piles Combined end bearing and friction piles Laterally loaded piles

Bored/Drilled piles
Cast-in-situ concrete Combination of Both

Non-displacement piles
Bored piles

TYPES OF PILES (contd.) Classification methods does not provide complete description of type of piles – First identified based on type of material Timber piles Concrete piles Steel piles Composite piles Special types of piles – Underreamed pile, screw pile/helical pile
Timber

Common Pile Shapes

H-pile

Circular (Solid/Hallow)

Square

Composite

Timber Piles

TIMBER PILES
Easy to handle; readily cut into desired length
Pine-23 m; Douglas Fir-37m

Diameter – 150 to 400 mm Capacity – up to 100 tons; restricted to 30 tons Fresh water – last long; but in salt water or above water surface, requires treatment and protected for decays Normally tappered; Best-suited as friction piles in granular deposits; also used in silts and clays Not recommended to use in dense gravel and as end bearing piles

3

Timber Piles

Timber Pile - Toe Protection

CONCRETE PILES
Precast concrete piles
Reinforced/Prestressed Mostly installed by driving Circular/octagonal/square/rectang le Must be designed for handing and d i i stresses d driving t Typical capacity – 300 tons Pile length – 12 to 15m (reinforced) and up to 40m (prestressed-pretensioned); posttensioned are in sections Suitable as end bearing pile; also used as friction piles in sand, gravel, clay

CONCRETE PILES (contd.) Cast-in-situ concrete piles
Placing concrete in hole (driving, boring, jetting, coring or combination of these methods) Mostly Circular Adv: No storage yards; designed for service loads, loads no cutting/splicing, pile length can be adjusted Cased/uncased piles – steel casing bentonite slurry can also be used to prevent caving

Diameter – 500 to 1000 mm Slump:- Cast-in-situ=75 to 100mm; Tremie placed concrete=150 to 200mm

CONCRETE PILES (contd.) Bored compaction piles
Installed by both driving and boring Boring is done Concreting the hole Then th Th the reinforcement i i f t is driven into the fresh concrete Improve the compactness of the concrete Pile diameter slightly is enlarged Bored compaction pile: More efficient: 1.5 to 2 Normal drilled pile

STEEL PILES
Strong, lightweight to handle, capable of carrying heavy loads Extended to any length; splicing is easy Pipe piles, H-section piles, tapered and fluted tubes: open-end/closed-end
Circular-pipe pile is preferred – cleaning of soil is easy, minimize the drag force due to wave/current and inspection for plumb is easier For hard bearing strata – conical points are attached at toe of hollow pipe

Best-suited for soft clays, silts and loose to medium dense sand underlain by dense bearing stratum Not recommended in dense gravel, boulders and hard bearing stratum Must be protected for corrosion in underwater environment/GWT

4

H-Pile Overview
TYPICAL LENGTHS TYPICAL DESIGN LOADS 5 m to 40 m. 45 to 235 tons

H-Piles

DISADVANTAGES

Vulnerable to Corrosion. Not Recommended as Friction Pile in Granular Soils. Available in Various Lengths and Sizes. Easy to Splice. High Capacity. Low Soil Displacements.

ADVANTAGES

REMARKS

Best Suited for Toe Bearing on Rock. May Penetrate Larger Obstructions with Driving Shoes.

H-Pile - Toe Protection

H-Pile - Splicing

Open End Pipe Pile Overview

Large Diameter Open Ended Pipe

TYPICAL LENGTHS

5 m to 50 m

TYPICAL DESIGN LOADS80 to 1500 tons. DISADVANTAGES ADVANTAGES Vulnerable to Corrosion Not suggested forfrictioin pile in granular material. Pile Can be Cleaned Out and Driven Deeper. High Capacity. Low Soil Displacements. Easy to Splice. High Bending Resistance on Unsupported Length.

5

Closed End Pipe Pile Overview
TYPICAL LENGTHS 5 m to 40 m 40 to 300 tons.

Typical Pipe Pile Closure Plate

TYPICAL DESIGN LOADS DISADVANTAGES ADVANTAGES

Soil Displacement Displacement. Various Lengths, Diameters & Wall thickness Easy to Splice. High Capacity Potential. Can be visually inspected before concreting High Bending Resistance Where Unsupported Length is Loaded Laterally .
Flat Closure Plate Fillet Weld

REMARKS

Conical Pipe Pile Tip

Pipe Pile - Splicing

Pipe Pile - Concreting

Prestressed Concrete

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Prestressed Concrete – pile cushion

Prestressed Concrete Details

Typical Sizes

25 – 50 cm

50 – 90 cm

25 – 60 cm

28 – 45 cm void

28 – 38 cm void (voids in larger only)

COMPOSITE PILES
Made by joining sections of two dissimilar materials together Concrete-timber, concrete-steel and concrete-filled steel pipes etc. Good joint is difficult in concretej timber pile -rarely adopted in practice Good concrete-steel joint can be achieved and economical

Composite Piles
TYPICAL LENGTHS TYPICAL DESIGN LOADS DISADVANTAGES ADVANTAGES 16 m to 67 m. 30 to 200 tons. May be Difficult to Attain Good Joint Between Materials. May Solve Unusual Design or Installation Problems. High Capacity Possible, Depending on Materials. May Reduce Foundation Cost. Weakest Material Governs Allowable Stresses & Capacity.

REMARKS

Composite Piles
Pipe – H-pile

Composite Piles
Corrugated Shell - Timber

Concrete – H-pile
Pipe - Concrete

7

SPECIAL TYPES OF PILES
Franki pile – expanded base compacted pile; Thermal piles; Grouted piles; Screw Piles; Anchor Piles; Underreamed pile etc.

PILE INSTALLATION
Driven piles
Equipment Rig, Hammers, Vibratory pile drivers, hammer cushion, drive head, pile cushion

PILE DRIVING HAMMER OPERATION
• Cast-in place systems
– Assumed that the contactor knows best and will establish procedures

SOME PILE DRIVING EQUIPMENT
• • • • Cranes Leads Helmets Cushions

• Driven piles
– Engineer must approve procedures in advance – Specifications often outmoded – “Just tell me the energy”

Fixed leads with kicker brace Air/Steam hammer with compressor mounted on crane

Swinging leads driving batter pile Air/steam hammer

8

H-pile helmet

Hammer cushion material

Plywood pile cushion

Hammer Types
External Combustion Internal Combustion

PILE INSTALLATION (contd.) Driven Piles: Typical Hammers

Drop hammer

Hydraulic hammer

Air/steam hammer

Open end diesel

Closed end diesel

9

Effect of pile driving in nearby buildings Bored Piles / special type piles
Equipment Drilling rig, augers, Belling tools, coring tools, hole bottom cleaning tools, casings

-- Tremie concreting

CHOICE OF PILE Factors to be considered:

Site Considerations on Pile Selection
Remote Areas May Restrict Equipment Size.

Soil and water conditions Availability of material Local experience Construction schedule Type of structure to be supported Overall economy – cost comparison must include estimation of cost of the entire foundation system (e.g., pile caps, grade beams etc.) rather than comparing the cost per pile

Available Crane Size May Restrict Pile Size Local Availability of Pile Materials Capabilities of Local Contractors. Waterborne Operations May Require Shorter Pile Sections due to handling limitations. Steep Terrain May Make Use of Certain Pile Equipment Costly Impossible. Driven Piles May Cause Vibrations. or

Subsurface Effects on Pile Selection
Typical Problem Boulders over Bearing Stratum Loose Cohesionless Soil Recommendation
Use Heavy Low Displacement Pile With Shoe. Include Contingent Predrilling Item in Contract. Use Tapered Pile to Develop Maximum Shaft Resistance.

Subsurface Effects on Pile Selection
Typical Problem Artesian Pressure Recommendation
Hydrostatic Pressure May Cause Collapse of Mandrel Driven Shell Piles and Thin Wall Pipe. Pile Heave Common on Closed End Pipe. Adequate Pile Capacity Should be Developed Below Scour Depth (Design Load x SF). Tapered Pile Should Be Avoided Unless Taper Extends Below Scour Depth. Use Prestressed Concrete Piles or High Strength Steel Closed End Pipe Piles Where Hard Driving is Expected.

Scour

Deep Soft Clay

Use Rough Concrete Piles to Increase Adhesion and Rate of Pore Water Dissipation.

Coarse Gravel Deposits

10

Pile Shape Effects on Pile Selection
Shape Characteristic Displacement Pile Types Closed End Steel Pi St l Pipe Placement Effects
Increase Lateral Ground Stress. Densify Cohesionless S il D if C h i l Soils.

Pile Shape Effects on Pile Selection
Shape Characteristic Low Displacement Pile Types Steel H-pile Placement Effects
Minimal Disturbance to Soil.

Prestressed Concrete

Temporarily Remolds and Weakens Cohesive Soils. Setup Time for Large Pile Groups in Sensitive Clays May Be Up To Six Months.

Open End Steel Pipe

Not Recommended for Friction Piles in Coarse Granular Soils. Piles Often Have Low Driving Resistances in These Deposits Making Field Capacity Verification Difficult and Resulting in Excessive Pile Lengths Installed.

Pile Shape Effects on Pile Selection
Shape Characteristic Tapered Pile Types Timber Monotube Tapertube Placement Effects Increased Densification of Soil. High Capacity for Short Penetration Depth in Granular Soils.

PILE QUALITY CONTROL/EXAMINATION
Need for pile quality inspection:
Defects in concrete piles caused either during or after construction Load testing of piles -- to check the assumptions adopted in the load capacity design of the piles -- Too expensive and time consuming Modern non-destructive methods -- based on small strain impulse p techniques enable the integrity of all the piles on a site to be established rapidly and economically to enhance greatly confidence in the foundation Pile Integrity Tester (PIT) Sonic-logging Test Pile Driving Analyzer (PDA)

PILE INTEGRITY TESTER (PIT) Equipment / Testing
Elastic rebound hammer, Pile Integrity Tester, Pickups and other accessories

PILE INTEGRITY TESTER (contd.)

Interpretation of Results
Time domain/frequency domain Based on arrival of reflected wave velocity Requires good skill and experience

11

SONIC LOGGING TEST Principle / Procedure / Analysis
In homogeneous concrete, sound velocity is constant, about 4000 m/s.
If velocity decreases rapidly, it p indicates the presence of defects such as soil inclusion, cracks or segregation

ANALYSIS & DESIGN OF PILES FOR STATIC LOADS Static Vertical Loads:
Load transfer by End bearing and skin friction

(Q v ) ult = Q p + Q f

Sonic logging is a continuous measurement of sound velocity along the pile between an emitting sensor and a receiving sensor lowered down two tubes Accurately detect the defects at each depth

Failure Patterns: Factors affecting the vertical load carrying capacity of piles

Soil conditions – Soil profile (homogeneous/nonhomogeneous, soil strength, thixotrophy / sensitivity, water table etc. Method of installation – Soil disturbance Type of pile -- Pile quality

Vertical load carrying capacity of piles: Method of Analysis (contd.)

Vertical load carrying capacity of piles: Method of Analysis By utilizing soil strength By utilizing soil strength (initial soil strength) Empirical analysis by utilizing standard field tests
Standard penetration test values Cone Penetration test values Pressuremeter tests

(Q v ) ult = Q p + Q f
End Bearing

Dynamic driving resistance
By pile driving formula By wave equation analysis

Q p = Ap (cN c + 0.5γBN γ + γD f N q )
Skin Friction

Full-scale pile load tests

Q f = p ∑ f s ΔL
L =0

L= L

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Vertical load carrying capacity: Piles in Cohesionless soils End Bearing

Vertical load carrying capacity: Piles in Cohesionless soils (contd.)

Qp = Ap (cNc + 0.5γBNγ + γDf Nq )
Cohesion = 0; since B is very small, the second term is generally ignored

Skin Friction

Earth pressure co-efficient (Ks)
Pile type Bored cast-in-situ pile Driven H-pile Driven precast pile Driven cast-in-situ pile Ks 1.0 – 2.0 0.5 – 1.0 1.0 3.0 10–30 1.0 – 3.0

Q f = p ∑ f s ΔL
L =0

L= L

Unit skin friction

Q p = Ap γ D f N q

′ f s = ca + σ h tan δ

′ Q p = Apσ v N q
IS Code: Based on Berezantseu’s curve for D/B of 20 up to φ= 35o and Vesic’s curves beyond φ > 35o; included the effect of Nγ

′ f s = σ h tan δ
′ f s = K sσ v tan δ

Note: Lower value for loose sand and higher value for dense sand Imp. Note: Over burden pressure is constant beyond the critical depth: 10 to 30 d; generally taken as 20 d (d = diameter )

Vertical load carrying capacity: Piles in Cohesionless soils (contd.)

Vertical load carrying capacity: Piles in Cohesionless soils (contd.)

Friction Coefficient, f = tan δ, where friction angle between pile and soil as follows: δ = tan-1 (2/3 tan φ) where φ is the angle of internal friction of soil. Typical Values for different pile material
Pile Material Steel Concrete Timber δ 0.67 to 0.83 φ 0.90 to 1.00 φ 0.80 to 1.00 φ

Empirical Analysis (Based on SPT data) End bearing
− _ 0 .4 N D f Ap ≤ 4 N Ap B

Unit skin friction
_

Q* = p

f s* =

N ≤1tsf f 50

_

Where N is the average corrected SPT value (for end bearing near the pile tip; for skin friction along the pile length)
Note: Qp is in tons and fs is in tons/ft2

Vertical load carrying capacity: Piles in Cohesive soils End Bearing

Vertical load carrying capacity: Piles in Cohesive soils (contd.)

Effective pile length (Le) Skin Friction

Qp = Ap (cNc + 0.5γBNγ + γDf Nq )
Angle of friction = 0; Nq = 1.0, Nγ = 0

Q f = p ∑ f s ΔL
L =0

L= L

Unit skin friction

′ f s = ca + σ h tan δ

Type of soil Soft to very soft Medium stiff Stiff Stiff to hard

SPT- N value ≤4 4–8 8 – 15 > 15

Adhesion factor (α)
Bored Castin-situ Pile Driven Steel Pile

Qp = Ap (cNc + γDf )

f s = ca
Q f = p ∑ ca ΔL
L = Le

0.7 0.5 0.4 0.3

1.0 0.7 0.4 0.3

L =0 Ca = α Cu where, α is adhesion factor

13

Vertical load carrying capacity: Piles in Cohesive soils (contd.)

Vertical load carrying capacity: Piles in Cohesive soils (contd.)

Empirical Analysis (Based on SCPT data) Skin friction

Empirical Analysis (Based on SCPT data) End bearing

Vertical load carrying capacity of Piles Based on dynamic driving resistance Pile driving formulae:

Principle or work done

WH = Qdyn S + ΔE
WH = Qdyn S + Qdyn C

Qdyn = WH

S +C

Pile Group

Pile Group: Vertical capacity

Optimum pile spacing ranges from 3 to 3.5 times pile diameter Pile spacing: 3 to 7 times diameter – Group action Pile spacing: More than 7 times diameter – Individual

Minimum of Single pile capacity by the multiplied Pile arrived group using

number of piles capacity “Block

failure theory”

14

Interaction factor under vertical loads

Negative Skin Friction on Piles

Downward

movement

of

soil relative to the surface of pile will lead to negative skin f i ti (d ki friction (downward skin d ki friction) Will result in the reduction of the skin frictional resistance

ANALYSIS & DESIGN OF PILES FOR STATIC LOADS

Settlement of Pile: (cohesionless soil)

Static Lateral Loads:

S t = S s + S p + S ps
St = Total pile top settlement for a single pile Ss = Settlement due to axial deformation of a pile shaft Sp = Settlement of pile base or point caused by load transmitted at the base Sps = Settlement of pile caused by load transmitted along the pile shaft

Static Lateral Loads: Concept of Load resistance Retaining wall Pile

Static Lateral Loads: Concept of Load resistance (contd.)

15

Static Lateral Loads: Concept of Load resistance (contd.)

Static Lateral Loads: Concept of Load resistance (contd.)

Failure Patterns

Soil deformations

Sand

Clay

Static Lateral Loads: Concept of Load resistance (contd.)

Factors affecting the Lateral load carrying capacity of piles
Zone of influence

Soil parameters: Soil strength, thixotrophy/sensitivity, Modulus of subgrade reaction or Young’s modulus of soil Pile parameters: Pile diameter, Moment of inertia and Young’s modulus of pile material (or Flexural rigidity : EI of pile) Relative stiffness of soil-pile system

Static Lateral Loads: Classification of Piles

1.

Based on Failure mechanism i. Short pile (rigid pile) ii. Long pile (flexible pile)

2.

Based on pile head condition i. Free head pile ii. Fixed head pile

16

Static Lateral Loads: Different Classification Criteria
Source Broms (1964 a & b) Poulos & Davis (1980) Bierschwale et al. (1981) Dobry et al. (1982) Davies & Budhu (1986) Budhu D i B dh & Davies (1987) Carter & Kulhawy (1988) Poulos & Hull (1989) Criterion for Rigid Behavior βrL < 1.5 Kr > 10-2 L/d < 6 SH < 5 L < 1.5 d K0.36
0.222 L < 1.3 d K0 222 13

Criterion for Flexible Behavior βrL > 1.5 Kr < 10-5 L/d > 6 SH > 5 L > 1.5 d K0.36
0.222 L > 1.3 d K0 222 13

Note A B C D E F G H

Static Lateral Loads: Methods of Analysis

1.

Subgrade reaction approach (Brinch Hansen’s method, Broms method)

2. 3. 4.

Elastic Analysis p-y curve approach Elastic continuum approach

L/d < 0.05 (Ep/G*)0.5 L < Lc/3

L/d > (Ep/G*)2/7 L > Lc

Note: d = pile diameter (m), L = pile length (m), Ep = pile elastic modulus (kPa), Ip = pile moment of inertia (m4), Es = soil elastic modulus (kPa), νs = Poisson’s ratio of soil, Gs = soil shear modulus (kPa) A -βr = (khd / 4EpIp)0.25; kh = coefficient of subgrade reaction B -Kr = (EpIp / Esd4) = flexibility factor C -In some cases, may be rigid for L/d < 10 D -SH = (L/d) / (Ep / Es)0.25 = flexibility factor E -K = (Ep / Es) = stiffness ratio; for constant soil modulus with depth F -K = (Ep / md); m is Es rate of increase; for linear variation of soil modulus with depth G -G* = Gs (1+3 νs / 4) = modified soil shear modulus H -Lc = 4.44 (EpIp / Es)0.25 = critical pile length

Static Lateral Loads: Methods of Analysis (contd.) Static Lateral Loads: Methods of Analysis (contd.)

Subgrade reaction approach: Brinch Hansen's method

Sand/Clay
Subgrade reaction approach: Concept

Static Lateral Loads: Methods of Analysis (contd.)

Subgrade reaction approach: Brinch Hansen's method – Long Piles

Subgrade reaction approach: Brinch Hansen's method – Layered soils

17

Static Lateral Loads: Methods of Analysis (contd.)

Subgrade reaction approach: Broms method

Short pile

Clay

Sand

Static Lateral Loads: Methods of Analysis (contd.)

Subgrade reaction approach: Broms method Long pile (Flexible pile) Clay Sand

Static Lateral Loads: Methods of Analysis (contd.)

Elastic analysis

18

Elastic analysis (Reese and Matlock, 1956): Free head Pile (cohesionless soil)

Elastic analysis (Reese and Matlock, 1956): Free head Pile (cohesionless soil) – Coefficients for lateral load

Elastic analysis (Reese and Matlock, 1956): Free head Pile (cohesionless soil) – Coefficients for lateral load

Elastic analysis (Reese and Matlock, 1956): Free head Pile (cohesionless soil) – Coefficients for Moment loading

Elastic analysis (Reese and Matlock, 1956): Free head Pile (cohesionless soil) – Coefficients for Moment loading

Elastic analysis (Reese and Matlock, 1956): Fixed Head Pile (cohesionless soil)

19

Elastic analysis (Reese and Matlock, 1956): Fixed Head Pile (cohesionless soil)

Elastic analysis (Reese and Matlock, 1956): Fixed Head Pile (cohesionless soil)

Elastic analysis (Davission & Gill, 1963): Free Head Pile (cohesive soil)

Elastic analysis (Davission & Gill, 1963): Free Head Pile (cohesive soil)

Elastic analysis: Free & Fixed Head Pile subjected to both load and moment

Static Lateral Loads: Methods of Analysis (contd.)

p-y curve approach

20

Static Lateral Loads: Methods of Analysis (contd.)

Static Lateral Loads: Methods of Analysis (contd.)

p-y curve approach

p-y curve approach

Static Lateral Loads: Methods of Analysis (contd.)

Buckling of Piles under combined lateral and vertical loading

Elastic Continuum Approach

Pile group interaction factor under lateral loads
Static Uplift Loads

21

Static uplift Loads: Concept of Load resistance (single pile)

Failure surface of pile as given by Chattopadhyay and Pise Model (1986)
130

22

Static uplift Loads: Concept of Load resistance (pile group)

PILE BEHVIOUR DURING EARTHQUAKES 1964 Niigata earthquake, Japan

Sand or Coarse grained soil

Clay or Fine grained soil
Lateral spreading caused foundations of the Showa bridge to move laterally and collapsed

1995 Kobe earthquake, Japan (M=6.9)

Dynamic Soil-Pile-Structure Interaction

Collapse of the Hanshin Express way

Frequency dependent response of pile Nonlinearity of gapping in soil and soil of piles case

embedded in clays need to be accounted properly Even the reliable estimation single pile response in soft clays for earthquake loads is difficult

Nishinoya Bridge

Analytical and Numerical Studies Dynamic Analysis of Piles
• Linear Approaches Subgrade reaction method (Tucker, 1964) Lumped mass idealization method [Prakash and Chandrasekaran, 1973] Novak's continuum approach [Novak, 1974; Novak and Aboul-Ella 1978] Equivalent cantilever approach [Poulos and Davis, 1980] Beam-on-Winkler formulation [Kavvadas and Gazetas 1993; Makris 1994; Mylonakis ; ; y and Gazetas 1999; Mylonakis 2001; Catal 2002]

Methods of Analysis

• • •

Analytical and numerical methods Linear Approaches

Experimental Studies Small-scale experiments

• • •

Boundary element method [Trifunac, 1973; Sen et al. 1985; Pak and Jennings 1987;
Banerjee and Sen 1987]

Finite element method [Tajimi and Shimomura 1976; Blaney et al. 1976; Shimizu et al.
1977; Kuhlemeyer (1979); Waas and Hartmann 1981 & 1984; Angelides and Roesset 1981; Krishnan et al. 1983; Velez et al. 1983; Gazetas 1984]

Nonlinear Approaches

Full-scale experiments

23

Analytical and Numerical Studies (contd.)

ASEISMIC DESIGN OF PILES: SIMPLE METHOD Using the response spectrum Natural frequencies under lateral vibration for two different soil

Nonlinear Approaches

• Lumped mass idealization method [Penzien et al. 1964]
• Beam-on-Winkler formulation [Gazetas and Dobry 1984; Nogami and Chen
1987; Nogami et al. 1991 & 1992; Badoni and Makris 1996; El Naggar and Novak 1996; Pender and Pranjoto 1996; El Naggar and Bentley 2000; Arduino et al. 2002; j gg y Han 2002; Mostafa and El Naggar 2002]

conditions have been given. Frequency factor for both free head and fixed head also given as a non-dimensional charts For F constant soil modulus, t t il d l

• •

Boundary element method [Kucukarslan and Banerjee 2003] Finite element method [Kagawa and Kraft 1980 a & b; Wu and Finn 1997a & b;
Sawant and Dewaikar 1999]

ASEISMIC DESIGN OF PILES: SIMPLE METHOD (contd.)

ASEISMIC DESIGN OF PILES: SIMPLE METHOD (contd.)

For constant soil modulus,

For linearly-increasing soil modulus,

Response Spectrum

ASEISMIC DESIGN OF PILES: SIMPLE METHOD (contd.)

Data Required:
Soil characteristics (Bore log of site) Pile characteristics: size, EI, length and type of pile Lateral load-deflection of the pile under static conditions for estimation of ks or nh

Design Steps:
Estimate the soil modulus Compute the relative stiffness factor (R or T) Calculate the maximum depth factor Zmax (most cases Zmax >5) Read the frequency factor for the computed maximum depth factor Estimate the dead load on pile. The mass of the pile top which may be considered vibrating with the pile is only a fraction of this load. Determine the natural frequency and time period in the first mode of vibration

24

ASEISMIC DESIGN OF PILES: SIMPLE METHOD (contd.)

Coefficient: Ame
Design Steps: (contd.) For the time period, determine the spectral displacement Sd for assumed damping. Estimate the maximum BM For constant soil modulus, BM = Ame x kR2 x Sd For linearly-increasing modulus, BM = Bme x nhT3 x Sd The pile deflection all along the pile length can also be determined by assuming some deflection shape in vibrations similar to one under static conditions. The soil reaction is then computed using the following formulae:
3 0.255 0.315 0.93 0.90 0.10 0.28 Max. Depth factor 2 Pile top free to rotate 0.100 Max. Depth factor 2 3 5-15 Pile top free to rotate 0.13 0.24 0.32 Pile fixed at top against rotation Negative Positive 0.9 0.9 0.9 0.0 0.04 0.18

Coefficient: Bme
Pile fixed at top against rotation Negative 0.93 Positive 0.0

For constant soil modulus, px = k . yx For linearly-increasing modulus, px = nh . yx . x

5-15

Commercial Softwares for Analysis of Foundations of Bridges Deflection and Moment coefficients

FB-Deep

FB-Pier
Nonlinear Finite Element Analysis FB-Deep - Static; FB-MultiPier – Static and Dynamic

FB-MultiPier

Demo version at http://bsi-web.ce.ufl.edu/

Softwares for Seismic Analysis of Pile Foundations

WELL FOUNDATIONS

DYNOPILE (Adruino, 2002) PILE 3D (Wu and Finn, 1997) GeoFeap (Lok et al. 1998) PLAXIS 3D FLAC 3D

• Also known as caissons are like the pile foundation • Widely used in India as foundation for bridge piers and abutments • Also used in foundation in situations where the uplift loads are large, as in the case of transmission line towers

25

SHAPES OF WELL

DEPTH OF A WELL FOUNDATION

• Two important requirements that influence the depth of a well foundation • Minimum grip length below the scour depth • Base pressures to be within permissible limits

Scour occur at a bridge site
1) General scour that would occur in the stream within the bridge. 2) The scour that at the bridge site because of the construction in waterway caused by the bridge and the approach embankment

General Scour: Scour depth d = 0.473 ( Q / f ) 1/ 3

where, Q = design discharge in cm f = Lacey’s silt factor = 1.76 (m)0.5 m = mean size of particle in mm Local Scour: dls = 1.4 Cs Ba

3) The local scour that occurs because of distortion of the flow pattern in the immediate vicinity of the bridge piers and abutments.

Where, Ba = Average width of pier below the HFL above the general scour level, Cs = Cofficient which depends on the pier shape. = 1 for cylindrical piers = 1,4 for rectangular pie

FORECS ACTING ON WELL FOUNDATION

LATERAL STABILITY OF WELL FOUNDATION

1) Wind forces 2) Forces due to water currents 3) Force due to tractive effort of vehicles 4) Centrifugal forces in case the well is located on a curved. 5) Buoyancy 6) Earth pressure 7) Temperature 8) Seismic forces Banerjee and Gangopadhyay’s analysis IRC Method Terzaghi’s Analysis Pender’s analysis

Methods

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IRC METHOD IRC: 45-1972 recommends elastic theory method to estimate the soil pressure on the sides and at the base under design load. • Applicable for noncohesive soils like sand. • Recommendation will not apply if the depth of embedment is less than 0.5 times the with of foundation in the direction of lateral force.

Methods for rectifying tilt and shift a) Controlled dredging b) Eccentric loading c) Pulling the well d) Pushing the well e) Water jetting and or digging pit on the higher side f) Providing obstacles below cutting edge

a) Controlled dredging

b) Eccentric loading

c) Pulling the well

d) Pushing the well

f) Obstacles below cutting edge

e) W t jetting and/or digging piton the higher side ) Water j tti d/ di i it th hi h id

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