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Basic piling technologies

Classification of bearing pile types. After Weltman

and Little (1977) - from Fleming et al. (1994)


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DRIVEN PILES•PREFORMED PILES

•FRANKI PILES

•VIBRO PILES


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FRANKI PILES

CONSTRUCTION STAGES


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VIBRO PILES

CONSTRUCTION

STAGES


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VIBRO PILES

PILE DRIVING EQUIPMENT IN PLACE


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BOTTOM PLACEMENT

VIBRO PILES


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INSERTION OF THE REINFORCEMENT

VIBRO PILES


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CONTINUOUS FLIGHTAUGER PILES


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CONSTRUCTION STAGES


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FINISHED PILE



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BORED PILES


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THIRD MAINLANDBRIDGE

CONSTRUCTION

STAGES

STEEL CASING

INSTALLATION


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CONSTRUCTION

STAGES

BORING


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TOOL EXTRACTION


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THIRD MAINLANDBRIDGECONSTRUCTION STAGES



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CONSTRUCTION

STAGES

CONCRETE

CASTING BY

MEANS OF THE

TREMIE PIPE


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CONCRETE CASTING

FUNNEL AND TREMIE PIPE


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MICROPILESEQUIPMENT WEIGHT ABOUT 10 TONN

MAXIMUM DRILLING DEPTH ABOUT 60 m


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SELECTIVE INJECTION

MICROPILES

EXECUTION STAGES OF A MICROPILE INJECTED AT HIGH PRESSURE


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PILE TESTING

• LOAD TESTING

- Pile integrity and abilityto carry the load

- Load bearing and

deformation

carachteristics

• NON-DESTRUCTIVE

TESTING

- Quality control


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PILE LOAD TESTING

•IS A METHOD OF CHECKING THEPERFORMANCE OF A PILE

•THE TEST PILE SHOULD BETYPICAL IN ALL RESPECTS OF THEPILES IN THE FOUNDATION

•THE OBJECTIVES OF APRELIMINARY PILE TEST ARE:

-DETERMINE THE ULTIMATEBEARING CAPACITY, RELATINGTHIS TO THE DESIGN PARAMETERS;

- SEPARATE THE ADHESION ANDEND BEARING CAPACITY;

- DETERMINE THE STIFFNESS OFTHE SOIL/PILE SYSTEM


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PILE LOAD TESTSPROCEDURES

A) MAINTAINED LOAD TESTS (MLT)

The load is increased in definite steps, and

is sustained at each level of loading

until all settlements has either stop or

does not exceed a specified amount in a

certain given period of time.


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PILE LOAD TESTSPROCEDURES

B) CONSTANT RATE OF PENETRATION

TEST (CRP)

test pile is jacked into the soil, the load being

adjusted to give constant rate of

downward movement to the pile.

Failure of the pile is defined in two ways:

-the load at which the pile continues to move

downward without further increase in

load

or

-according to the BS , the load which the

penetration reaches a value equal to one-

tenth of the diameter of the pile at the

base


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NON-DESTRUCTIVETESTING

-INTEGRITY TESTING ARE QUALITYCHECKS BY INDIRECT METHODS

-MERITS AND LIMITATIONS

-TYPES OF INTEGRITY TESTS:

a) Acoustic tests

b) Radiometric tests

c) Seismic

d) Stress-wave tests

e) Dynamic response testsf) Electrical tests


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TUBE POSITIONING IN A DOUBLE – HOLE

ACOUSTIC TEST



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DOUBLE HOLE ACOUSTIC TEST-DISPLAY OF RESULTS-



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Single piles in vertical

(axial) loading

• Piles made from steel or reinforcedconcrete (formerly of timber) carrylarge point loads (eg from columns)

• Load transfer into the soil is throughside friction and base bearing

• Sometimes used to carry large loadsto a deep, firm foundation eg bedrock

• Piles can be driven into the ground orcast in place (“bored piles”)

• ULS design load is based on the“failure” load calculated using a

reduced soil strength• SLS (e.g. excessive settlements)must also be considered


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Skin friction and base

bearing for a single pile

• Skin friction will ADD to downward load if

ground swells relative to pile

• Pile may carry an upward load in which

case base bearing is not applicable


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Skin friction and base bearing

• Relative rates of mobilization of skinfriction and base bearing will depend

on method of pile installation


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Calculation of failure load

• Calculate base bearing capacity as for adeep foundation using appropriate bearing capacity equation

• Effective stress analysis: skin friction = pile area × normal (horizontal) effectivestress σ′h × soil/pile friction coefficienttanδ

• In a normally consolidated soil, σ′h =

(1-sinφ′).σ′v• In an overconsolidated soil K o

(=σ′h/σ′h) is greater in situ but may bereduced near the pile during installation

• Total stress analysis: skin friction = pilearea × soil/pile adhesion τw

• Soil pile adhesion often taken as α.τuwith α = 0.5 to allow for local softeningduring pile installation


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QT

q s

q b

W

s sS

bb B

S BT

AqQ

AqQ

QQW Q

⋅=

⋅=

+=+


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Non-cohesive soils:

γ γ N BqN cN q qcb2

1++=

q

vo

N

q 'σ =

Cohesive soils:

γ γ N BqN cN q qcb2

1++=

1

9

=

=

=

→

q

vo

c

u

N

q

N

cc

σ

End-bearing pressure


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Non-cohesive soils:

Cohesive soils:

Skin friction

u s cq ⋅=Short Term

stresseffectivenormal:

anglefrictioninterface:'''

'

'

0

'

0

'

h

V V h s tg K tg q

σ

δ βσ δ σ δ σ =⋅=⋅=

α- Empirical factor: 0,2÷1

Long Term

stresseffectivenormal:

anglefrictioninterface:'

''

'

'

0

'

0

'

h

V V h s tg K tg q

σ

δ

βσ δ σ δ σ =⋅=⋅=

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