1. The document describes different types of pile foundations, including classifications based on function and material.
2. Pile foundations are deep foundations used when shallow foundations are unsuitable due to weak soil. They transfer loads to deeper, stronger soil layers using end bearing, friction, or both.
3. Piles are classified by function as end bearing, friction, compaction, tension, anchor, fender, or sheet piles. Materials used include concrete, steel, timber, composites, and sand. Common pile types are described for each category.
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1. INRODUCTION
What is Foundation:-
A foundation is the lowest part of the building structure.
It is the engineering field of study devoted to the design of those structures
which support other structures, most typically buildings, bridges or
transportation infrastructure.
It is at the periphery of Civil, Structural and Geotechnical Engineering
disciplines and has distinct focus on soil-structure interaction.
It is also called as ground sill, which transfers loads to the ground. It is
generally broken into two categories.
1) Shallow foundation
2) Deep foundation
Types of Foundation:-
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2. PILE FOUNDATION
What is Pile Foundation:-
Pile foundations are deep foundations used when the site has a weak shallow
bearing strata making it necessary to transfer load to a deeper strata either by
friction or end bearing principles.
Foundations provide support for structures by transferring the load to the rock
or layers of soil that have sufficient bearing capacity and suitable settlement
characteristics.
There are a very wide range of foundations types available which are suitable
for different applications.
Foundations are classified mainly as Shallow foundations and Deep
foundations.
Uses Pile Foundation:-
a) End Bearing or Compressive Strength –
Sometimes we use the piles to achieve the required compressive
strength in the soft soil; in that case we use the piles to transfer the load
through that soft soil to a suitable bearing stratum by using the end
bearing or toe bearing property of the pile
b) Scour Depth:
To build a structure within the water and on the water river or canal
bed; we have to build the foundation through the river bed and within
the scour depth.
c) Tension or Uplift:
Piles are usually used to carry compressive nature of load through tip
bearing or end bearing; but in case of tall structures or like towers there
might be tension that must be resisted by piles. For example for a
tower carrying high power transmission lines the thrust of wind might
produces over turning that must be resisted by the tension piles;
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d) Vibration Control:
For foundation of buildings supporting vibrating equipments like
Turbines and silos etc where the vibrations is significant and might
cause failures as well; there are two options there you might go for the
massive block to absorb the vibrations or you can use the deep
foundations and same that the massive block is very uneconomical.
e) Compaction Piles:
Sometimes the piles are driven in a weaker strata of soil to increase the
bearing capacity of the soil those piles are called compaction piles; and
thus by using compaction piles we can increase the bearing capacity of
the soil.
3. TYPES OF PILE FOUNDATION BASED ON
FUNCION
1) END BEARING PILE :-
End-bearing piles develop most of their load-bearing capacity at the
toe of the pile, bearing on a hard layer of rock or very dense soil and
gravel.
The pile transmits the load through soft, compressible strata directly
onto firm strata. This type of pile therefore acts in the same way as a
column.
The pile transmits the load to the surrounding soil by adhesion or
friction between the surface of the pile and the soil. In this case, the
whole surface of the pile works to transfer load to the soil.
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2) FRICTION PILE:-
Friction (or floating) piles develop most of the pile-bearing capacity by shear
stresses along the sides of the pile, and are suitable where harder layers are too
deep to reach economically.
The pile transmits the load to surrounding soil by adhesion or friction between
the surface of the pile and soil, which in effect lowers the bulb of pressure.
In other words, the whole surface of the pile (cylindrical in shape) works to
transfer the forces to the soil.
Friction piles are in contrast to end-bearing piles which develop most of their
load-bearing capacity at the toe of the pile, bearing on a hard layer of rock or
very dense soil and gravel.
FIG.NO. 3.1.1
FIG.NO. 3.2.1
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3) COMPACTION PILE :-
Sand compaction piles are one of the potential methods for improving ground
stability, preventing liquefaction, reducing settlement and similar applications.
This method involves driving a hollow steel pipe into the ground.
The bottom is closed with a collapsible plate down to the required depth and
then pipe is filled with sand.
The pipe is withdrawn while the air pressure is directed against the sand inside
it.
The bottom plate opens during withdrawal and the sand backfills the voids
created earlier during the driving of the pipe. The sand backfill prevents the
soil surrounding the compaction pipe from collapsing as the pipe is
withdrawn. During this process, the soil gets densified.
4) TENSION PILE:-
Tension piles, also known as uplift piles or anchor piles, are a type of pile
foundation that is used to resist uplift forces that might otherwise cause it to be
extracted from the ground.
Uplift forces can develop as a result of hydrostatic pressure, seismic activity or
overturning moments. In particular, tall structures such as chimneys, jetties
and transmission towers can be subject to high wind loads and hence,
overturning moments. The compressive and tensile forces generated must be
transmitted to the ground along the length of the pile.
FIG.NO. 3.3.1
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5) ANCHOR PILE:-
Anchor Piles are required to resist lateral loads with or without being braced
depending on circumstances and an ordinary or standard house pile is required
to carry a vertical load.
The Anchor Pile is used in a more critical application and therefore the
strength characteristics have much greater values associated, compared to that
of an ordinary pile.
6) FENDER PILE:-
The piles used to protect concrete deck or other water front structures from the
abrasion or impact that may be caused from the ships or barges (when they are
tied up at the desk), are called fender piles.
The fender piles are originally made up to timber.
FIG.NO. 3.4.1
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7) SHEET PILE:-
Sheet piles are commonly used for retaining walls, land reclamation,
underground structures such as car parks and basements, in marine locations
for riverbank protection, seawalls, cofferdams, and so on.
Timber sheet piles are generally used for short spans in temporary structures,
and to resist light lateral loads. They are typically connected together by
tongue and groove joints.
The disadvantage of timber piles is that they require preservative treatment
and are not generally suitable for soils consisting of stones.
FIG.NO. 3.7.1
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4. TYPES OF PILE FOUNDATION BASED ON
MATERIAL
1) CONCRETE PILES :-
RAYMOND PILE :-
It is used primarily as a friction pipe.
It is uniform heavy taper of 1 in 30 result in short piles for equal driving
resistance or higher driving resistance for equal lengths, than piles of lesser or
no taper.
This pile is 6 to 12m long and it has 20cm to 30cm diameter.
PILES
CONCRETE
PILES
STEEL PILES
TIMBER
PILES
COMPOSITE
PILE
SAND PILE
FIG.NO. 4.1.1
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MAC-ARTHUR PILES :-
It have a uniform diameter, using the corrugated steel shell which remains in
place.
A heavy steel casing with a core is driven into the ground.
When it reaches the desired depth, the core is withdrawn, and a corrugated
steel shell is placed in the casing.
Finally, concrete is filled in the corrugated steel shell and outer hard casing is
removed after gradually compacting it.
SWAGE PILES:-
The swage piles are used with advantage in some soils where the driving is
very hard.
These piles are designed to leave watertight shell for some time before filling
the concrete.
A shell (Thin steel pipe) is placed on the concrete plug and steel core.
Shell is driven over the plug until the core reaches the plug; the pipe is swaged
out by taper of the plug, thus forming a watertight joint.
Once the shell has reached the desired depth, the core is removed, and the
shell is filled with concrete.
FIG.NO. 4.1.2
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BUTTON BOTTOM PILES:-
The button bottom piles are used in locations where an increase in the bearing
area at the end is desired.
The pile uses a concrete plug that is button shaped. This is how the pile
derives its name.
During driving, this button forms an enlarged hole in the soil.
These piles have been used up to lengths of about 23 m and load up to 50
tonnes capacity.
A steel pipe and reinforced base of cast steel are set over the concrete button.
The pipe and button are driven to a specified depth; corrugated steel shell is
then inserted in the pipe, and rested on the button.
FIG.NO. 4.1.3
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SIMPLEX PILES :-
Simplex piles can be driven into soft or hard soils.
In this type of pile, a steel tube fitted with a cast iron shoe is driven into the
ground up to the desired depth.
After that, reinforcement is provided in the tube and then filled it with
concrete. Tube is gradually withdrawn, leaving behind the cast iron shoe at the
bottom.
FIG.NO. 4.1.4
FIG.NO. 4.1.5
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FRANKIE PILES:-
Franki piles have an enlarged base of the mushroom shape, which gives the
effect of a spread footing.
This pile is useful where a bearing stratum of limited thickness can be reached
at a reasonable depth.
Franki pile is best suited to granular soil.
A heavy removable shell consisting gravel or concrete are set on the ground
with the help of leads.
Some portion of concrete is placed in the tube and ramming is done with
hammer.
The tube held in position by lead and hammer is applied to the concrete,
forcing it down and outward.
As a result, the enlargement of the base into the mushroom shape taken place.
The shaft is formed by successive charges of concrete, ramming each in turn,
and gradually withdrawing the casing.
FIG.NO. 4.1.6
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VIBRO PILES:-
In these piles, a steel tube, fitted with a cast iron shoe is driven in the ground
by the hammer.
When the shoe and the tube reaches the desired level, the hammer is fitted at
the top of the tube.
The tube is withdrawn when concrete is consolidated in each downward blow.
Thus, the concrete is being forced down to occupy the space left by the tube,
resulting in corrugated face of the pile.
The corrugated face gives rise to increased frictional resistance and
consequently, increases the bearing capacity.
PEDSTAL PILES:-
Pedestal piles are used where thin bearing stratum is reached with reasonable
depth.
In these piles, the pedestal gives the effect of spread footing.
The core and casing are driven together into the ground, till they reach up to
the desired level.
FIG.NO. 4.1.7
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The core is taken out and concrete is placed in the tube.
The core is replaced in casing till it rests on top of the poured concrete.
The concrete is rammed out, thus resulting in the formation of the pedestal.
The core is removed; the casing is filled with concrete.
PRESSURE PILES :-
Pressure piles are formed with the help of a casing tube, boring auger and
compressed air equipment.
These piles are especially suitable for those congested sites where heavy
vibration and noise are not permissible.
A boring tool, such as an auger working inside it, excavates the soil. The
bored soil is continuously taken out, and the hole is cleaned
FIG.NO. 4.1.8
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UNDER-REAMED PILE:-
An under-reamed pile is a bored cast-in-situ concrete pile having one or more
bulbs or under reams at its lower portion.
The bulbs or under reams are formed by under reaming tool.
When only one bulb is provided at the base, it is known as a single under-
reamed pile.
When two or more bulbs are provided at the bottom, it is known as multi-bulb
under-reamed pile.
These piles are best suited in soils where substantial and significant
movements prevail due to seasonal discrepancy.
FIG.NO. 4.1.9
FIG.NO. 4.1.10
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2) STEEL PILE:-
H-PILES:-
H- Piles are usually of wide flange section.
H-piles are dimensionally square structural beams.
They are driven in the ground for deep foundation applications.
They have a small cross-sectional area; therefore, they can be easily driven in
soils in which it will be difficult to drive ordinary displacement piles.
They are used as long piles with high bearing capacity.
PIPE PILES :-
The pipe piles are driven either open-ended or close-ended.
Pipe piles are designed to transfer structural loads through the foundation to
strata below.
As the open-ended piles are sunk in the ground, the soil inside the pipe is
cleaned out simultaneously.
In case of closed-end piles, the driving of each pipe is closed by welding
conical steel or cast-iron shoe to the pipe end.
FIG.NO. 4.2.1
FIG.NO. 4.2.2
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SCREW-PILES:-
Screw piles consist of cast iron or steel shaft of an external diameter generally
varying 15 to 30 cm and terminating into a helix or screw base.
The diameter of the screw at its bottom varies from 45 cm to 150 cm.
These piles are used when the soil has poor load bearing capacity.
Screw piles are a type of deep foundation that can be installed quickly with
minimal noise and vibration.
DISC PILES:-
A disc pile consists of hollow metallic pipe attached with a cast iron disc to its
foot to enlarge the bearing area of the pile.
Disc pile can be used mostly in marine installations or in sandy or wet soils
which may permit sinking of the pile by water jets, thereby providing
penetration of the pile in an enlarged area.
FIG.NO. 4.2.3
FIG.NO. 4.2.4
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3) TIMBER PILES :-
Timber piles are prepared from trunks of trees like sal, teak, deodar, babul,
khair etc.
At the bottom, a cast-iron shoe is provided and at the top, a steel plate is fixed
in this pile.
These piles have a small bearing capacity and are not permanent unless
treated.
Timber piles prove economical for structures to be located in compressive
soils constantly saturated with water.
4) COMPOSITE PILES:-
This is a type of construction in which piles of two different materials are
driven one over the other, so as to enable them to act together to perform the
function of a single pile.
In composite pile the upper and lower portions consists of different types of
materials. Thus, it takes advantage of good qualities of both the materials.
FIG.NO. 4.3.1
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5) SAND PILES :-
Sand piles are formed by making holes in the ground and then filling them
with sand.
If sand is confined, it possesses great crushing strength and becomes in
compressible.
They are basically used for compaction. Thus, they increase the bearing
capacity of soil.
FIG.NO. 4.4.1
FIG.NO. 4.5.1
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REFERENCE
Page no. 79-99, cl. 3.1-3.13, Building construction, Sushil kumar.
https://gharpedia.com/pile-foundation-types-classifications/
https://en.wikipedia.org/wiki/Deep_foundation
https://www.designingbuildings.co.uk/wiki/Pile_foundations