Pile foundations are used to transfer structural loads through weak surface soils to stronger deeper soils or bedrock. They consist of long slender members called piles that are driven or bored into the ground. Piles can be made of concrete, steel, or wood. Common types include precast concrete piles, H-piles, and bored piles. Pile foundations are used when subsurface soil cannot support the loads from the structure, in areas with weak or compressible soils, and where deeper soils are needed to support heavy loads. They allow structures to be built in places that could not otherwise support them.
3. What is Pile Foundation?
Construction of foundation of a abutment or pier supported on piles.
a column usually of RCC that is driven into the foundation soil or constructed
inside the foundation soil.
the part of structure used to carry & transfer load of the structure to the
bearing ground located at some depth below ground surface.
Main components of Pile Foundation
Piles are long slender members which transfer the load to deeper soil or rock
of high bearing capacity avoiding shallow soil of low bearing capacity.
Pile caps are thick slabs used to tie a group of piles together to support &
transmit column loads to the piles.
Advantages of Pile Foundation
Frequently needed because of the relative inability of shallow footings to
resist inclined, lateral, uplift and overturning moments.
Used in areas of expansive or collapsible soils to resist undesirable seasonal
movements of the foundations used for any type of structure and soil.
now-a- days used instead of well and caisson foundation.
Can be used in any type of soil.
Where are they used?
When stratum of required bearing capacity is at greater depth.
Where soil is compressible, water logged or of made up type.
6. Displacement piles are
driven or otherwise forced
into the ground to displace
subsoil, such as solid piles
or piles inside tubes, closed
at their lower ends by shoe
or plug.
Non-displacement piles are
formed by boring or other
methods of excavation that
do not displace subsoil &
where bore hole is lined with
casing or tube left or
8. PRECAST PILES
Sizes vary from 300-450 mm length
of a side & upto 18 m or more in
length, piles upto 1.5 m dia are also
available.
reinforced with mild steel bars of 20-
38 mm dia, stirrups usually 6-8 mm
dia.
Increase in lateral reinforcement at
end assist in withstanding high
stresses developed during driving.
strengthened at head for higher
stresses, upper 500-900 mm by use of
stronger grade of concrete.Driven Piles
• formed by driving a precast pile &
those made by casting concrete in
hole formed by driving.
• Square, polygonal, round sections
are cast in moulds, cured, to devlop
max. strength.
• Placing reinforcement, mixing,
placing compaction & curing of
concrete for piles of uniform strength
& cross section.
9.
10.
11. Soil condition Type of pile
(recommended)
• soil consists of slit for
appreciable depth.
•Tapered pile
•Soil is very weak or loose •Cast-in-situ pile with casing to
prevent inflow of soil into the pile
•Soil is subjected to strong water
flow
•Precast pile with permanent casing
•Strata is firm • Uncased cast-in-situ or precast pile
•Soil is firm clay •Drilled piles(with or without enlarged
base)
•In case piling is to be done very
near to some existing structure
•Open ended tube pile or H-pile
12. End Bearing
&
Friction Piles
Piles that
• transfer load mainly by end bearing at the pile
point or base to compact gravel, hard clay or
rock are termed as end bearing piles.
• transfer load mainly by friction to clays and
silts are termed as friction piles.
13. Driven Cast in place Piles
• two types- first one has
permanent steel or concrete
casing & second is without
permanent casing.
• Precast concrete shells are
threaded on a steel mandrel.
• Metal bands & bitumen seal
joints between shells.
• Mandrel & shell are lifted on to
the piling rig & then driven into
ground.
• at reqd. depth mandrel is
removed, a reinforcing cage is
lowered into shell & concrete
casted inside.
A Standard Pile
14. Driven Cast in place Pile without
permanent casing
• formed by driving a lining tube
with cast iron shoe into ground
with a piling hammer operating
in pile rig.
•piles formed thru sub-stratum
so compact so as to be
incapable of being taken out by
drilling.
•Standard piles made in sizes of
350, 450, 500 mm dia , larger
loads of 600-750- kN, formed in
length of 25 m & over.
• cast shoe iron is driven until
desired set has been obtained
by 2000-2500 kg hammer,
delivering 40 blows per minute
with stroke of upto 1.4 m.
• cage of reinforcement is
lowered down the tube, tube
filled with concrete. Extracting
links are is fitted to hammer &
top of tube.
•Withdrawal of tube & ramming
is effected by hammer blows,
filling left space & forming
corrugations.
15. Driven Cast in place Pile without
permanent casing
• a steel tube is pitched with its lower end
resting on the ground at a spot the hole
has to be formed.
• The base of a steel lining tube,
supported on a piling rig, is filled with
ballast & tube into the ground at reqd.
depth the tube is restrained & ballast is
hammered to form an enlarged toe.
• The effect of driving the tube & ballast
into ground is to compact the soil around
the pile & subsequent hammering of the
concrete consolidates it into weak
packets & weak strata.
• Enlarge toe provides additional bearing
area at the base of the pile to act as
friction pile. When tube has been driven
to required depth, held by cables,
hammering is continued to free the plug &
force it downwards below the bottom of
the tube.
• Reinforcement cage is lowered &
successive charges of concrete down the
tube & as each is rammed, tube is
partially extracted about 300mm at a
time.FRANKI COMPRESSED PILE
16. SIMPLEX PILE
Simplex standard type
• formed by driving a 400-450 mm dia steel tube , with fitted
cast-iron shoe, until reqd. set is reached. Reinforcement cage
is inserted & after charging concrete, extracting gear is
attached & tube is slowly withdrawn leaving shoe behind.
Simplex tamped piles
• Tube is driven, reinforcement is lowered into position & tube
is filled to the level required for the top of the completed pile.
The extracting gear is fitted, tube is withdrawn with downward
blows at every few centimeters by drop hammer blow. The
tamping is repeated until completion.
Simplex bulb or extended piles
• The tube with its fitted conical shoe is driven down to a
satisfactory set. After partially filled with one or more batches
of dry concrete, the remaining tube is filled with mixture of
coarse aggregate & sand (2:1).Tube is withdrawn, second
shoe is fitted to get enlarged bulb, reinforcement is lowered &
tube after filled with concrete is withdrawn. Two shoes are left
behind
Simplex alligator jaw piles
• A mild steel tube with a cast iron alligator jaw point attached
with hinges at its lower end is used for forming pile of up to 6m.
The jaws are closed before driving is commenced. After being
lowered to required depth the tube is filled with concrete. The
weight of concrete causes the jaws to open, permitting the
concrete to flow freely from the tube.
18. BORED PILES
•Situations where vibrations would endanger
stability of the adjacent bldgs. Where noise
would create a nuisance & headroom is
restricted. A cheaper form of equipment is
needed for small no. of piles.
• A hole is drilled to withdraw soil from the
hole to cast the pile.
• usually steel lining tubes are lowered or
knocked in, to maintain the sides of drilling.
As the pile is cast the lining tubes are
gradually withdrawn.
• advantages are they are light, easily
manipulated equipment may be used &
precise analysis of subsoil strata is
obtained.
• disadvantage is that it is not possible to
check if concrete is properly compacted &
adequate cover is there.
• Because of irregular shape of the surface
of finished pile it acts as a friction pile.
PRESSURE PILES, PNEUMATIC
CAISSON PILES ,
PRESTCORE PILES ARE FEW
EXAMPLES
See Mc-kay Vol. 4 for details.
21. Advantages of cast-in –situ piles:-
•They are casted as per the required length. Therefore no wastage of
time ,money and material.
•they are not subjected to the vibrations due to hammers.Hence they are
sound in construction.
•No cost of transportation of the piles.
•It is possible to calculate the load bearing capacity of the pile for design
accuracy as the nature of the bearing strata and the end bearing pile is
known.
•They can be made to bear heavier loads by adopting pedestal pile
method.
Disadvantages of cast-in –situ piles:-
•Cannot be used under water.
•Reinforcement can get displaced.
•As concrete is dumped from great height, the quality of work is
not appreciably good.
•Freshly laid concrete in the cast –in-situ pile is more susceptible
to attack by corrosive constituents in the soil and the sub soil
water.
•The driving of adjacent piles may rupture sheet less cast –in-situ
pile on account of the tensile stresses set up in the ground during
driving.
22.
23. JACKED PILES
• designed for use in cramped working conditions.
• where the wall to be underpinned has strong concrete base are the pile
sections are jacked into the ground under the base & concrete cap is cast
on the top of the pile & up to the underside of concrete base.
• when wall to be underpinned has poor base, then pair of piles are
jacked in each side of the wall to support steel or RCC to support the
weight of the wall.
24.
25. Disadvantages of concrete piles compared to timber piles:-
• Being heavy in weight difficult to handle & transport.
• exact length of a pile can rarely be predetermined & as such it has to be
lengthened sometimes , rendering the pile weak at the joint.
• If found too long after driving, it has got to be cut down which involves
extra labour, time and expense.
• Can be subjected to the driving shocks after the concrete has fully set.
This may result in unsound construction.
• Cost is more compared to the timber pile.
• They cannot be driven rapidly.
• They must be reinforced to withstand handling stresses.
• They require technical supervision and heavy driving machines.
26. Advantages of concrete piles compared to timber piles:-
• Durability of concrete piles is independent of the ground water level
• Can be casted to any length,size or shape.
• Can be used for marine works without any treatment.
• Material required for manufacturing them is easily obtainable.
• Bond with pile cap can be easily done compared with timber body where
it is not perfectly achievable.
• They can be manufactured in bulk well before the work.
• Their construction can be well supervised and any defect detected can
be rectified before use.
• The reinforcements remain in their proper position and do not get
displaced.
• They can be driven under water.
• They can be loaded soon after they have been driven to the desired
depth.
27. Advantages of timber piles:-
• Economical
• Can be driven rapidly and therefore saving of time
• Can be recommended for sites where piles are subjected to unusual lateral
forces.
• Do not need heavy machinery and elaborate technical supervision.
Disadvantages of timber piles:-
• Conditions to decay or deteriorate by salt water or insects.
• Low bearing capacity
• Due to restricted length they cannot be used for jobs where long piles are
needed.
• Transmission of load:- by frictional resistance of the ground and the
pile surface.
• Suitable for:- light structures located in compressive soils constantly
saturated with water.
• Made from:- timber obtained from trees like Sal , teak , deodar ,
babul , khair.
• Khair can withstand action of sea water better and are thus commonly
used for marine works.
• Timber piles may be circular or square in cross section.
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29.
30.
31. SHEET PILES
• Used for many purposes like:
• enclosing a site or part thereof to prevent escape of loose
subsoil & so safeguard against any settlement any structure
which is to be erected on it.
• retaining sides of trenches & general excavations.
• forming cofferdams (watertight compartments as for
foundations on water).
• construction of retaining walls in docks & similar marine
works.
• coastal defense works- as protection against sea erosion
etc.
• river bank protection.
• to be effective it must have close contact with each other &
various types of joints are used.Types of Sheet Piles:
• Steel sheet pile- Box piles
•Reinforced concrete sheet piles
• Timber sheet piles
