CHAPTER 5 DEEP FOUNDATION (2)7788788.ppt

2.  Those that transfer the load at a point far
below the substructure.
 Deep foundation are used when adequate soil
capacity is not available close to the surface
and loads must be transferred to firm layers
substantially below the ground surface.
 The common deep foundation system for
buildings are caissons and piles.

3.  A pile can be defined as a column inserted in the
ground to transmit the structural loads to a
lower level of subsoil.
 The construction process of pile can be broadly
characterised by the installation and testing.
 However, there are many proprietary types of
piles and the testing process for each type
differed.
 Pile may be classified by the way there are
formed i.e. Displacement piles (END BEARING)
and non displacement piles (FRICTION).

4.  Pile may be classified as either End bearing
or Friction piles, according to the manner in
which the pile loads are resisted.
 However, in actual practice, virtually all piles
are supported by a combination of skin
friction and end bearing.

5.  The shafts of the piles act as columns
carrying the loads through the overlaying
weak subsoils to firm strata into which the
pile to has penetrated.
 This can be rock strata or a layer of firm
sand or gravel which has been compacted by
the displacement and vibration encountered
during the driving.

7.  Any foundation imposes on the ground a
pressure which spreads out to form a
pressure bulb.
 If a suitable load bearing strata cannot be
found at an acceptable level, particularly in
stiff clay soils, it is possible to use a pile to
carry this pressure bulb to a lower level
where a higher bearing capacity is found.
 The friction or floating pile is mainly
supported by adhesion or friction action of
the soil around the perimeter of the pile
shaft.

9. Types of Piles
Large displacement Small displacement Non displacement
Preformed solid or
hollow, closed at the
bottom end driven into
the ground and left in
position
Formed in-situ by driving
a closed-ended tubular
section to form a void,
and then filling the void
with concrete by
withdrawing the section
Steel sections,
includes H-piles,
open ended
tubes and box-
piles
Screw-piles A void is formed by
boring or excavation,.
The void is filled with
concrete. The sides of
the voids are:
Supported Unsupported
Permanently
(by casing)
Temporarily
Solid Hollow
Various
Systems
(closed at bottom and
filled or unfilled after
driving)
Timber
Precast
Steel tubes or box-piles
Concrete tubes
By casing
By drilling mud

10.  Displacement piles refer to piles that are
driven, thus displacing the soil, and include
those piles that are preformed, partially
preformed or cast in place.
 This is the most cost efficient piling method
but may not be suitable for areas sensitive to
noise, vibration and dust.
 The present of boulders can also hinder the
use of driving piles.

11.  Types of Displacement piles:-
1) Precast reinforced concrete piles
2) Steel preformed piles
3) Composite piles
4) Driven in situ/Cast-in-Place piles

12.  Come in different sizes and lengths, they are
driven by drop hammers using a piling rig.
 They provide high strength and resistance to
decay.
 They are however heavy, and because of its
brittleness and low tensile strength, cares in
handling and driving is required.
 Cutting requires the use of pneumatic
hammers, cutting torches, etc.

16.  H-piles or universal steel beam in the form of
wide-flange is commonly used.
 They do not cause large displacement and is
useful where upheaval of the surrounding
ground is a problem.
 There are capable of supporting heavy loads,
can easily cut and can be driven to great
depth.
 The driving method for steel piles is similar
to that of precast reinforced concrete piles.

17.  The handling and lifting of a steel pile is less
critical due to its high tensile strength.
 Lengthening of steel piles is through welding.
 Care must be taken in the welding of joints
to ensure that they are capable of
withstanding driving stresses without failure.
 A protective steel guard should be welded at
the joints when necessary.

19.  Also referred to as partially preformed piles,
composite piles combine the use of precast
and in situ concrete and/or steel.
 They are an alternative to bored and
preformed piles for sites with the presence
of running water or very loose soils.
 The common generic types are the shell piles
and cased piles

21.  The pile shaft is formed by using a steel tube
which is either top driven or driven by means
of an internal drop hammer working on a
plug of dry concrete/gravel as in Franki
piles.
 Piles up to 610mm can be constructed using
this method.

22.  With temporary casing, as the casing is
withdrawn during the placing/compacting of
concrete, precautions need to be taken when
working at depth with groundwater
movement to prevent problems associated
with necking (narrowing) caused when the
groundwater washes away some of the
concrete thus reducing the effective
diameter of the pile shaft and consequently
the concrete cover.

24.  Sometime referred to as replacement piles
but more commonly as bored pile.
 They are formed by boring/removing a
column of soil and replaced with steel
reinforcement and wet concrete cast through
a funnel or tremie pipe.
 For soft grounds and where the water table
is high, bentonite may be used during boring
to resist the excavation and water inflow
before casting.

25.  Bored piles are considered for sites where
piling being is being carried out in a close
proximity to existing buildings where
vibration, dust and noise need to be
minimised.

26.  Superstructure design
 Site area
 Soil condition
 Surrounding buildings and structures
 Availability of equipment and site constraints

28.  Pile are driven by drop hammers using a
piling rig.
 Hammer will be drop to pile head with
allowable height that have been determine
until it reach ‘set’ (pile has reach the hard
strata).

29. 1. Set out the position of each pile and
establish the temporary benchmarks (TBM)
on site to determination of cut-off levels of
piles.
2. Check the verticality of the piling rig using
a plumb or spirit level.
3. Provide markings along the pile section to
enhance recording of penetration and to
serve as rough guide to estimate the set
during driving.

30. 4. Install mild steel helmet. protect pile
head/joint plate with packing or cushioning
within e.g. a 25 mm thick plywood between
the pile head and helmet.
5. Hoist up and place the pile in position
5. Check on verticality regularly
6. Proceed with the hammering. Monitor pile
penetration according to the markings on
pile. When the rate of penetration is low,
monitor pile penetration over 10 blows.

31. Hold one end of a pencil supported firmly
on a timber board not touching the pile.
The other end of the pencil marks the pile
displacement on a graph paper adhered on
the pile over 10 blows.
8. Stop piling if the displacement is less than
the designed displacement over 10 blows.
Otherwise, continue with the piling
process.

32. 8. Lengthening of pile can be done by means
of a mild steel splice sleeve and a dowel
inserted in and drilled through the centre
of the pile.
9. The connection is sealed by welding the
pile head/joint plate which are pre-
attached to both ends of a pile in
manufacturing process.

33. 1. Heavy steel casing is closed at the end
with a plug of dry concrete
2. Plug of concrete, driven with a drop
hammer, expands, grips the sides of the
casing and takes the casing into the
ground.
3. On reaching the required depth the
casing is restrained by cables and the
plug of concrete is driven out into the
ground to form a bulb at the end of the
pipe

34. 4. Cage or reinforcement is placed
5. Casing is filled with concrete as the
casing is withdrawn

37.  This is a new technique used for the
installation of pile.
 Using hydraulic machine to inject the pile
into the ground until the pile reach the
require depth.
 The depth required is base on the working
load, this can be determine by reading
pressure on the dial gauge.
 Example, if the pile working load are 12
tones, the ‘set’ taken will be 24 tones which
is double from the working load.

39.  This method uses a vibro hammer to install
the pile into ground.
 The vibro hammer will hold the pile head
and transfer the vibration to the end of the
pile toe.
 The vibration will then be transferred to the
ground and the shear strength of the soil is
reduced.
 This will enable the pile to be installed into
the ground using the vibro hammer and the
pile own weight.
 This method is suitable to be used on soft

41.  This method is using excavation machine
which are percussion or rotary.
 The hole are formed by boring/removing a
column of soil and replaced with steel
reinforcement and wet concrete cast through
a funnel or tremie pipe.
 This method are used for bored pile and
micro pile.

44.  Piles are generally driven closely together in
clusters that contain from two to twenty-five
piles each
 The piles in each cluster are later joined at the
top by a reinforced concrete pile cap, which
distributes the load of the column or wall
equally among the piles
 Clusters of two, three, four and nine piles with
their concrete caps. The caps are reinforced to
transmit column loads equally into all the piles
in the cluster

46.  The main objective of forming test piles is
to confirm that the design and formation of
the chosen pile type is adequate.
 Pile load tests give information on the
performance of the pile, installation
problem, lengths, working loads and
settlements.

47.  Static load tests involve the use of a heavy
load or reaction method to counter the
application of an axial load to the top of the
test pile using one or more hydraulic jacks.
 The main objectives of static load test are:-
1. to determine the ultimate failure load
2. capability of supporting a load without
excessive or continuous displacement
3. to verify that the allowable loads used for
the design of a pile are appropriate and
that the installation procedure is
satisfactory.

48.  Two types of loading are commonly used:-
i. Maintained load test
 also referred to as working load test, which
load is increased at fixed increment up to
1.5 to 2.5 times its working load.
 settlement is recorded with respect to
time of each increment.
 when the rate of settlement reaches,
maintain the load for 12 hours.

49. ii. Ultimate load test
 The pile is steadily jacked into the ground
at a constant rate until failure.
 The ultimate bearing capacity of the pile is
the load at which settlement continues to
increase without any further increase of
load or the load causing a gross settlement
of 10% of the pile diameter.

50.  This is only applied to test piles which must
not be used as part of the finished
foundations but should be formed and tested
in such a position that will not interfere with
the actual contract but is nevertheless truly
representative of site conditions.

52.  Dynamic load test is an direct method using
the wave propagation theory to estimate the
condition of a hammer-pile-soil system.
 The method involves the process of
impacting the tested pile with a large drop
weight and measuring the compressive stress
wave travelling down the pile.
 Transducers and accelerometers are installed
near the top of the pile to measure the
reflected wave.

53.  Using measurements of strain and
acceleration and principles of wave
mechanics, performance such as static pile
capacity and pile integrity can be estimated.

55.  Sheet piling comprises a row of pile which
interlock with one another to form a
continuous wall which may be temporary or
permanent.
 It consists of rolled steel sections with
interlocking edge joints.
 The interlocking edges allow each sheet pile
to slide into the next relative ease, and
together they form a steel sheet wall that
serves the purpose of retaining the soil and
to some extent, exclusion of ground water.

56.  The standard length of sheet pile is 12m.
Longer piles are achieved by joining sections
together by either welding or splicing or
both.

57. 57
Z-Type (Z)
Used for intermediate to deep
wall construction
Larson / “U” Type (U)
Used for applications similar to Z –
Type
Flat / Straight Type (SA), (S)
Used for filled cell construction
Arch shaped & lightweight
Used for shallower wall construction

58. 58
Typical types
of interlocks
Ball & Socket (BS)
Single Jaw (SJ)
Double Jaw (DJ)
Hook & Grip (HG)
Thumb & Finger
one point contact (TFX)
Double Hook (DH)
Thumb & Finger
three point contact (TF)