PILE FOUNDATION Session 17 – 26 Course: S0825/Foundation Engineering Year: 2009

PILE FOUNDATIONSession 17 – 26

Course : S0825/Foundation EngineeringYear : 2009

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PILE FOUNDATIONS

Topic:• Types of pile foundation• Point bearing capacity of single pile• Friction bearing capacity of single pile• Allowable bearing capacity of single pile

SESSION 17 – 20

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INTRODUCTION

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TYPES OF PILE FOUNDATION

STEEL PILE

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CONCRETE PILE

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CONCRETE PILE

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WOODEN PILE

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COMPOSITE PILE

COMBINATION OF:

- STEEL AND CONCRETE

- WOODEN AND CONCRETE

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PILE CATEGORIES

Classification of pile with respect to load transmission and functional behaviour: 1. END BEARING PILES

These piles transfer their load on to a firm stratum located at a considerable depth below the base of the structure and they derive most of their carrying capacity from the penetration

resistance of the soil at the toe of the pile

2. FRICTION PILES

Carrying capacity is derived mainly from the adhesion or friction of the soil in contact with the

shaft of the pile

3. COMPACTION PILES

These piles transmit most of their load to the soil through skin friction. This process of driving such piles close to each other in groups greatly reduces the porosity and compressibility of the

soil within and around the groups.

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END BEARING PILE

PILE CATEGORIES

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PILE CATEGORIES

FRICTION PILE

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PILE CATEGORIESClassification of pile with respect to effect on the soil

- Driven Pile

Driven piles are considered to be displacement piles. In the process of driving the pile into the ground, soil is moved radially as the pile shaft enters the ground. There may also be a

component of movement of the soil in the vertical direction.

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PILE CATEGORIES

Classification of pile with respect to effect on the soil

- Bored PileBored piles(Replacement piles) are generally considered to be non-displacement piles a void is formed by boring or excavation before piles is produced.

There are three non-displacement methods: bored cast- in - place piles, particularly pre-formed piles and grout or concrete intruded piles.

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PILE CATEGORIES

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DETERMINATION OF PILE LENGTH

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BEARING CAPACITY OF PILE

Two components of pile bearing capacity:

1. Point bearing capacity (QP)

2. Friction bearing capacity (QS)

SPU QQQ

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BEARING CAPACITY OF PILE

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POINT BEARING CAPACITY

SQUARE FOUNDATIONqu = 1,3.c.Nc + q.Nq + 0,4..B.N

CIRCULAR FOUNDATIONqu = 1,3.c.Nc + q.Nq + 0,3..B.N

For Shallow Foundation- TERZAGHI

- GENERAL EQUATIONidsqiqdqscicdcsu F.F.F.N.B..5,0F.F.F.Nq.qF.F.F.Nc.cq

Deep Foundationqu = qP = c.Nc* + q.Nq* + .D.N*

Where D is pile diameter, the 3rd term of equation is neglected due to its small contribution

qu = qP = c.Nc* + q’.Nq* ; QP = Ap .qp = Ap (c.Nc* + q’.Nq*)

Nc* & Nq* : bearing capacity factor by Meyerhof, Vesic and Janbu

Ap : section area of pile

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POINT BEARING CAPACITYMEYERHOF

PILE FOUNDATION AT UNIFORM SAND LAYER (c = 0)

QP = Ap .qP = Ap.q’.Nq* Ap.ql

ql = 50 . Nq* . tan (kN/m2)

Base on the value of N-SPT :

qP = 40NL/D 400N (kN/m2)

Where:N = the average value of N-SPT near the pile point (about 10D above and 4D below the pile point)

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PILE FOUNDATION AT MULTIPLE SAND LAYER (c = 0)

QP = Ap .qP

dlblldl

llP qD

10Where:

ql(l) : point bearing at loose sand layer (use loose sand parameter)

ql(d) : point bearing at dense sand layer (use dense sand parameter)

Lb = depth of penetration pile on dense sand layer

ql(l) = ql(d) = 50 . Nq* . tan (kN/m2)

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QP = Ap (c.Nc* + q’.Nq*)For saturated clay ( = 0), from the curve we get:

Nq* = 0.0

Nc* = 9.0

QP = 9 . cu . Ap

PILE FOUNDATION AT SATURATED CLAY LAYER (c 0)

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• BASE ON THEORY OF VOID/SPACE EXPANSION• PARAMETER DESIGN IS EFFECTIVE CONDITION

QP = Ap .qP = Ap (c.Nc* + o’.N*)

Where:o’ = effective stress of soil at pile point

Ko = soil lateral coefficient at rest = 1 – sin Nc*, N* = bearing capacity factors

cot1**

POINT BEARING CAPACITYVESIC

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According to Vesic’s theory

N* = f (Irr)

Irr = Reduced rigidity index for the soil

Ir = Rigidity index

Es = Modulus of elasticity of soil

s = Poisson’s ratio of soil

Gs = Shear modulus of soil

= Average volumetric strain in the plastic zone below the pile point

tan'tan'12 qc

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For condition of no volume change (dense sand or saturated clay):

= 0 Ir = Irr

For undrained conditon, = 0

The value of Ir could be estimated from laboratory tests i.e.: consolidation and triaxial

Initial estimation for several type of soil as follow:

Type of soil Ir

Sand 70 – 150

Silt and clay (drained) 50 – 100

Clay (undrained) 100 – 200

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POINT BEARING CAPACITYJANBU

QP = Ap (c.Nc* + q’.Nq*)

cot1**

.tan1tan* tan'22

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POINT BEARING CAPACITYBORED PILE

QP = . Ap . Nc . Cp

Where: = correction factor = 0.8 for D ≤ 1m = 0.75 for D > 1mAp = section area of pilecp = undrained cohesion at pile pointNc = bearing capacity factor (Nc = 9)

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FRICTION RESISTANCE

fLpQs ..Where:

p = pile perimeterL = incremental pile length over which p and f are taken constantf = unit friction resistance at any depth z

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FRICTION RESISTANCESAND

fLpQs ..

tan'.. vKf

Where:K = effective earth coefficient = Ko = 1 – sin (bored pile) = Ko to 1.4Ko (low displacement driven pile) = Ko to 1.8Ko (high displacement driven pile)v’ = effective vertical stress at the depth under consideration = soil-pile friction angle = (0.5 – 0.8)

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FRICTION RESISTANCECLAY

Three of the presently accepted procedures are:

1. methodThis method was proposed by Vijayvergiya and Focht (1972), based on the assumption that the displacement of soil caused by pile driving results in a passive lateral pressure at any depth.

2. method (Tomlinson)

3. method

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FRICTION RESISTANCECLAY - METHOD

avs fLpQ ..

uvav cf 2' Where:v’= mean effective vertical stress for the entire embedment lengthcu = mean undrained shear strength ( = 0)

VALID ONLY FOR ONE LAYER OF HOMOGEN CLAY

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LcLcc uuu

..... 22,11,

FOR LAYERED SOIL

...' 321

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fLpQs ..

For cu 50 kN/m2 = 1

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fLpQs ..

'. vf Where:

v’= vertical effective stress

= K.tanR

R = drained friction angle of remolded clay

K = earth pressure coefficient at rest

= 1 – sin R (for normally consolidated clays)

= (1 – sin R) . OCR (for overconsolidated clays)

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FRICTION RESISTANCEBORED PILE

LpcQ us 45.0

Where:

cu = mean undrained shear strengthp = pile perimeterL = incremental pile length over which p is taken constant

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ULTIMATE AND ALLOWABLE BEARING CAPACITY

SPU QQQ

QQ Uall

5.13SP

FS= 2.5 - 4

DRIVEN PILE

BORED PILE

QQ D < 2 m and with expanded at pile point

no expanded at pile point

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EXAMPLEA pile with 50 cm diameter is penetrated into clay soil as shown in the following figure:

GWL5 m

NC clay = 18 kN/m3

cu = 30 kN/m2

R = 30o

OC clay (OCR = 2) = 19.6 kN/m3

cu = 100 kN/m2

R = 30o

Determine:1. End bearing of pile2. Friction resistance by , , and methods3. Allowable bearing capacity of pile (use FS = 4)

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PILE FOUNDATIONS

Topic:• Settlement of Piles• Laterally Loaded Piles• Pull Out Resistance of Piles• Pile Driving Formula• Negative Skin Friction

SESSION 21 – 22

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SETTLEMENT OF PILES

S = S1 + S2 + S3

Where:

S = total pile settlement

S1 = elastic settlement of pile

S2 = settlement of pile caused by the load at the pile tip

S3 = settlement of pile caused by the load transmitted along the pile shaft

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SETTLEMENT OF PILES

Where:

Qwp = load carried at the pile point under working load condition

Qws = load carried by frictional (skin) resistance under working load condition

Ap = area of pile cross section

Ep = modulus of elasticity of the pile material

L = length of pile

= the magnitude which depend on the nature of unit friction (skin) resistance distribution along the pile shaft.

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SETTLEMENT OF PILES

DqS .1

Where:qwp = point load per unit area at the pile point = Qwp/Ap

D = width or diameter of pileEs = modulus of elasticity of soil at or below the pile points = poisson’s ratio of soilIwp = influence factor = r

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SETTLEMENT OF PILES

QS .1 23

Where:

Qws = friction resistance of pile

L = embedment length of pile

p = perimeter of the pile

Iws = influence factor

LIws 35.02

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EXAMPLE

The allowable working load on a prestressed concrete pile 21 m long that has been driven into sand is 502 kN. The pile data are as follow:

- Diameter (D) = 356 mm

- The area of cross section (Ap) = 1045 cm2

- Perimeter (p) = 1.168 m

Skin resistance carries 350 kN of the allowable load, and point bearing carries the rest. Use Ep = 21 x 106 kN/m2

, Es = 25,000 kN/m2, s = 0.35 and = 0.62)

Determine the settlement of the pile.

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EXAMPLE

mm35.3m00353.0

10x211045.0

2135062.0152

mm5.15m0155.085.035.01000,25

1045.0

152I.1

D.qS 2

mm84.0m00084.069.435.01000,25

21168.1

350I.1

69.4356.0

2135.02

L35.02Iws

S = S1 + S2 + S3 = 3.35 + 15.5 + 0.84 = 19.69 mm

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LATERALLY LOADED PILE

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ELASTIC SOLUTION – EMBEDDED IN GRANULAR SOIL

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LATERALLY LOADED PILEFor L/T 5

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ELASTIC SOLUTION – EMBEDDED IN COHESIVE SOIL

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ULTIMATE LOAD ANALYSIS – MEYERHOF – PILES IN SAND

ULTIMATE LOAD RESISTANCE (Qu(g))

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LATERALLY LOADED PILEMAXIMUM MOMENT, Mmax DUE TO THE LATERAL LOAD Qu(g)

MAXIMUM MOMENT, Mmax DUE TO THE LATERAL LOAD Qg

For long (flexible) piles in sand

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ULTIMATE LOAD ANALYSIS – MEYERHOF – PILES IN CLAY

ULTIMATE LOAD RESISTANCE (Qu(g))

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MAXIMUM MOMENT, Mmax DUE TO THE LATERAL LOAD Qu(g)

MAXIMUM MOMENT, Mmax DUE TO THE LATERAL LOAD Qg

For long (flexible) piles

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PULL OUT RESISTANCE OF PILES

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EXAMPLE:

A concrete pile 50 long is embedded in a saturated clay with cu = 850 lb/ft2. The pile is 12 in. x 12 in. in cross section. Use FS = 4 and determine the allowable pullout capacity of the pileSolution

Given cu = 850 lb/ft2 40.73 kN/m2

’ = 0.9 – 0.00625cu = 0.9 – (0.00625)(40.73) = 0.645

kip4.274

kip7.1091000

)850)(645.0)(1x4)(50(c'..p.LT

un)all(un

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For dry soils, the equation simplifies to

Determine the value of Ku and from figure 9.36b and 9.36c.

tan.....tan.....2

1 2crucrucrun LLKLpKLpT

allun )(

Where Tun(all) = allowable uplift capacity and FS is Factor of Safety (a value of 2 – 3 is recommended)

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EXAMPLE:

a precast concrete pile with a cross section 350 mm x 350 mm is embedded in sand. The length of pile is 15 m. Assume that sand = 15.8 kN/m3, sand = 35o, and the relative density of sand = 70%. Estimate the allowable pullout capacity of the pile (FS = 4)

Solution

From figure 9.36, for = 35o and relative density = 70%

LLKLpKLpT

unallun

crucrucrun

tan.....tan.....2

35351;1

08.5)35.0)(5.14(;5.14

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PILE DRIVING FORMULA

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NEGATIVE SKIN FRICTION

Can occur under condition such as:

- If a fill of clay soil is placed over a granular soil layer into which a pile is driven, the fill will gradually consolidate. This consolidation process will exert a downward drag force on the pile during a period of consolidation

- If a fill of granular soil is placed over a layer of soft clay. It will induce the process of consolidation in the clay layer and thus exert a downward drag on the pile

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CLAY FILL OVER GRANULAR SOIL

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NEGATIVE SKIN FRICTIONGRANULAR SOIL FILL OVER CLAY

THE UNIT NEGATIVE SKIN FRICTION AT ANY DEPTH FROM z = 0 TO z = L1

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GROUP PILES

Topic:• Bearing Capacity of Group Piles• Group Efficiency• Piles in Rock• Consolidation settlement of Group Piles

SESSION 23 – 24

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GROUP PILES

Lg = (n1 – 1)d + 2(D/2)

Bg = (n2 – 1)d + 2(D/2)

Where:

D = pile diameter

d = spacing of pile (center to center)

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GROUP PILES

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GROUP EFFICIENCY

Where:

= group efficiency

Qg(u) = ultimate load bearing capacity of the group pile

Qu = ultimate load bearing capacity of each pile without the group effect

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GROUP PILES IN SAND

uug Qnnp

If < 1 Qg(u) = .Qu

If 1 Qg(u) = Qu

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GROUP PILES IN SAND

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GROUP PILES IN SAND

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GROUP PILES IN SAND

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GROUP PILES IN SAND

Summary:

1.For driven group piles in sand with d 3D, Qu(g) may be taken to be Qu, which includes the frictional and the point bearing capacities of individual piles.

2.For bored group piles in sand at conventional spacings (d 3D), Qg(u) may be taken to be 2/3 to 3/4 times Qu (frictional and point bearing capacities of individual piles)

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GROUP PILES IN SATURATED CLAY

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GROUP PILES IN SATURATED CLAYCalculation steps:1. Determine Qu = n1.n2 (Qp + Qs)

where:QP = 9 . cu . Ap (ultimate end bearing capacity of single pile)

QS = (.p.cu.L) (skin resistance of single pile)

2. Determine the ultimate capacity by assuming that the piles in the group act as a block with dimensional Lg x Bg x L as follow :- end bearing capacity of the block

QP’ = Ap . qp = Ap . cu . Nc* with Ap = Lg . Bg

- Skin resistance of the blockQS’= (pg.cu.L) = 2.(Lg+Bg).cu.L

- Ultimate bearing capacity o pile groupQu = QP’ + QS’ Qu = (Lg . Bg) . cu . Nc* + 2.(Lg+Bg).cu.L

3. Compare the values obtained in step 1 and 2 the lower of the two values is Qg(u)

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Problem:

The section of a 3 x 4 group pile layered saturated clay. The piles are square in cross section (14 in. x 14 in.). The center to center spacing, d, of the piles is 35 in. Determine the allowable load bearing capacity of the pile group. USE FS = 4

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PILES IN ROCK

For point bearing piles resting on rock, most building codes specify that Qq(u) = Qu, provided that the minimum center to center spacing of piles is D + 300 mm. For H-Piles and piles with square cross sections, the magnitude of D is equal to the diagonal dimension of the pile cross section.

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CONSOLIDATION SETTLEMENT OF GROUP PILES

The Terzaghi formula is valid with some rules:

1.The consolidation settlement is occurred from the depth of 2/3 of pile length.

2.The stress increase caused at the middle of each soil layer by using 2:1 method

gi zLzB

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sat = 18,9 kN/m3

Cc = 0,2

eo = 0,7sat = 19 kN/m3

Cc = 0,25

eo = 0,75

Problem:

A group pile with Lg = 3.3 m and Bg = 2.2 m as shown in the figure. Determine the consolidation settlement of the pile groups. All clays are normally consolidated.

CONSOLIDATION SETTLEMENT OF GROUP PILES

sat = 18 kN/m3

Cc = 0,3

eo = 0,82

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ELASTIC SETTLEMENT OF GROUP PILES

• VESIC

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• MEYERHOF (Pile groups in sand and gravel)

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• PILE GROUP SETTLEMENT RELATED TO THE CONE PENETRATION RESISTANCE

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UPLIFT CAPACITY OF GROUP PILES

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UPLIFT CAPACITY OF GROUP PILES

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PILE INSTALLATION AND LOADING TEST

Topic:• Installation Method of Driven Pile• Installation Method of Bored Pile• Loading Test by Static Method• Loading Test by Dynamic Method

SESSION 25 – 26

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INSTALLATION METHOD

Pile Installation Equipment

The primary tools used in the actual driving(installing) of piles are :

• Impact Hammers,• Vibrator Driver / Extractors• Special Hydraulic Presses• Supporting Equipment – power sources, hoisting & material handling equipment, etc.

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PILE INSTALLATION EQUIPMENTS

Types of Impact Hammers

Impact Hammers are identified by their method of operation or the motive force employed. They are generally identified as :• Drop Hammers• Air or Steam Hammers• Diesel Hammers• Hydraulic Impact Hammers

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Drop Hammers

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Air (or Steam) Hammers

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Air (or Steam) Hammers

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Diesel Hammers

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Diesel Hammers

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Hydraulic Impact Hammers

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Hydraulic Impact Hammers

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Vibro Driver/Extractors

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Vibro Driver/Extractors

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Hydraulic Press Installer

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Hydraulic Press Installer

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Land Based RigsCantilever Fixed Lead

(With Fixed Bottom Brace) (With Spotter)

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Land Based Rigs

Under slung Swinging Lead

(With Fixed Bottom Brace) (With stabbing points)

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Land Based RigsEuropean Style, Fixed Lead with Fixed Bottom Brace

(Driving Aft Batter with Hydraulic Hammer)

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Land Based RigsEuropean Style, Fixed Lead on Crawler Lower

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DRIVEN PILE INSTALLATION

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BORED PILE INSTALLATION

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PILE QUALITY

Two aspects of final quality of pile:– Structural integrity of pile.– Pile ability to support external load, consist of strength

of structure element and relationship load-settlement between pile and soil support

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STATIC LOADING TEST

TEST METHODS– Use Static Load– The load is 200% of working load– Preparation before testing– Loading– Measurement of pile movement– Instrumentation

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STATIC LOADING TEST

• Loading Methods– Standard Method of Loading‑SML, Monotonic– Standard Method of Loading‑SML, cyclic– Quick Load Test (Quick ML)– Constant Rate of Penetration Method (CRP)

Sumber : Manual Pondasi Tiang, GEC

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Anchor Pile

Typical arrangements for axial compressive

load test

Dead Load

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STATIC LOADING TEST

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STATIC LOADING TEST

Test load arrangement using kentledge

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DYNAMIC LOADING TEST

• PDA (Pile Driving Analyzer) • DLT (Dynamic Load Test), TNO• Theory of wave propagation

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Strain gauge and accelerometerPDA computer

Interpretation of PDA

result

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PULL OUT TESTS

Pullout load by using hydraulic jack between beam and reaction frame (ASTM D 3689-83, 1989)

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PULL OUT TESTS

Pullout load by using hydraulic jack, one at each end of the beam (ASTM D 3689-83, 1989)

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LATERAL LOADING TEST

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LATERAL LOADING TEST

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PILE INTEGRITY TEST

• This test is needed to check the integrity of bored pile or driven pile.

• Some methods generally adopted is by using the principle of wave propagation. The test is carried out by applying vibration and evaluating its reflection.

• Through this test, the defect on pile will be able to detect.

PILE FOUNDATION Session 17 – 26 Course: S0825/Foundation Engineering Year: 2009

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