9. piled foundations_website
TRANSCRIPT
-
8/9/2019 9. Piled Foundations_website
1/34
Basic piling technologies
Classification of bearing pile types. After Weltman
and Little (1977) - from Fleming et al. (1994)
-
8/9/2019 9. Piled Foundations_website
2/34
DRIVEN PILES•PREFORMED PILES
•FRANKI PILES
•VIBRO PILES
-
8/9/2019 9. Piled Foundations_website
3/34
FRANKI PILES
CONSTRUCTION STAGES
-
8/9/2019 9. Piled Foundations_website
4/34
VIBRO PILES
CONSTRUCTION
STAGES
-
8/9/2019 9. Piled Foundations_website
5/34
VIBRO PILES
PILE DRIVING EQUIPMENT IN PLACE
-
8/9/2019 9. Piled Foundations_website
6/34
BOTTOM PLACEMENT
VIBRO PILES
-
8/9/2019 9. Piled Foundations_website
7/34
INSERTION OF THE REINFORCEMENT
VIBRO PILES
-
8/9/2019 9. Piled Foundations_website
8/34
CONTINUOUS FLIGHTAUGER PILES
-
8/9/2019 9. Piled Foundations_website
9/34
CONTINUOUS FLIGHTAUGER PILES
CONSTRUCTION STAGES
-
8/9/2019 9. Piled Foundations_website
10/34
CONTINUOUS FLIGHTAUGER PILES
INSERTION OF THE REINFORCEMENT
-
8/9/2019 9. Piled Foundations_website
11/34
FINISHED PILE
CONTINUOUS FLIGHTAUGER PILES
-
8/9/2019 9. Piled Foundations_website
12/34
BORED PILES
-
8/9/2019 9. Piled Foundations_website
13/34
THIRD MAINLANDBRIDGE
CONSTRUCTION
STAGES
STEEL CASING
INSTALLATION
-
8/9/2019 9. Piled Foundations_website
14/34
THIRD MAINLANDBRIDGE
CONSTRUCTION
STAGES
BORING
-
8/9/2019 9. Piled Foundations_website
15/34
THIRD MAINLANDBRIDGE
TOOL EXTRACTION
-
8/9/2019 9. Piled Foundations_website
16/34
THIRD MAINLANDBRIDGECONSTRUCTION STAGES
INSERTION OF THE REINFORCEMENT
-
8/9/2019 9. Piled Foundations_website
17/34
THIRD MAINLANDBRIDGE
CONSTRUCTION
STAGES
CONCRETE
CASTING BY
MEANS OF THE
TREMIE PIPE
-
8/9/2019 9. Piled Foundations_website
18/34
THIRD MAINLANDBRIDGE
CONCRETE CASTING
FUNNEL AND TREMIE PIPE
-
8/9/2019 9. Piled Foundations_website
19/34
MICROPILESEQUIPMENT WEIGHT ABOUT 10 TONN
MAXIMUM DRILLING DEPTH ABOUT 60 m
-
8/9/2019 9. Piled Foundations_website
20/34
SELECTIVE INJECTION
MICROPILES
EXECUTION STAGES OF A MICROPILE INJECTED AT HIGH PRESSURE
-
8/9/2019 9. Piled Foundations_website
21/34
PILE TESTING
• LOAD TESTING
- Pile integrity and abilityto carry the load
- Load bearing and
deformation
carachteristics
• NON-DESTRUCTIVE
TESTING
- Quality control
-
8/9/2019 9. Piled Foundations_website
22/34
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
-
8/9/2019 9. Piled Foundations_website
23/34
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.
-
8/9/2019 9. Piled Foundations_website
24/34
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
-
8/9/2019 9. Piled Foundations_website
25/34
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
-
8/9/2019 9. Piled Foundations_website
26/34
TUBE POSITIONING IN A DOUBLE – HOLE
ACOUSTIC TEST
NON-DESTRUCTIVETESTING
-
8/9/2019 9. Piled Foundations_website
27/34
DOUBLE HOLE ACOUSTIC TEST-DISPLAY OF RESULTS-
NON-DESTRUCTIVETESTING
-
8/9/2019 9. Piled Foundations_website
28/34
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
-
8/9/2019 9. Piled Foundations_website
29/34
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
-
8/9/2019 9. Piled Foundations_website
30/34
Skin friction and base bearing
• Relative rates of mobilization of skinfriction and base bearing will depend
on method of pile installation
-
8/9/2019 9. Piled Foundations_website
31/34
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
-
8/9/2019 9. Piled Foundations_website
32/34
Calculation of failure load
QT
q s
q b
W
s sS
bb B
S BT
AqQ
AqQ
QQW Q
⋅=
⋅=
+=+
-
8/9/2019 9. Piled Foundations_website
33/34
Calculation of failure load
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
-
8/9/2019 9. Piled Foundations_website
34/34
Calculation of failure load
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 =⋅=⋅=