Pile Foundation Types and Uses in Civil Engineering Projects

1
Civil Engineering
Practice
CEP - 8
Pile Foundation
Muhammad Usman Arshid

FOUNDATIONS
• Foundations provide support for structures, transferring their load to layers of
soil or rock that have sufficient bearing capacity and suitable settlement
characteristics.
• There are a very wide range of foundation types suitable for different
applications, depending on considerations such as:
• The nature of the load requiring support.
• Ground conditions.
• The presence of water.
• Accessibility.
• Sensitivity to noise and vibration.
• Proximity to other structures.
• Project timeframes.
Muhammad Usman Arshid

FOUNDATIONS
• Very broadly, foundations can be categorised as
shallow foundations or deep foundations.
• Shallow foundations are typically used where the loads
imposed by a structure are low relative to the bearing
c a p a c i t y o f t h e s u r f a c e s o i l s .
• Deep foundations are necessary where the bearing
capacity of the surface soils is insufficient to support
loads imposed and so they are transferred to deeper
l a y e r s w i t h h i g h e r b e a r i n g c a p a c i t y .

---(Pile Foundation)---
• Pile foundations are deep foundations. They are formed by long,
slender, columnar elements typically made from steel or
reinforced concrete and sometimes timber.
• Pile foundations are principally used to transfer the loads from a
superstructure, through weak, compressible strata or water onto
stronger, more compact, less compressible and stiffer soil or
rock at depth,
• They are used for large structures, and in situations where the
soil under is not suitable to prevent excessive settlement.
• Piles are required for setting out of towers for high power
transmission lines and in some cases are also used for supporting
the multistory buildings.

Situations Which Demand Pile Foundations
 Sub-soil water table is so high that it can easily affect the
other foundations.
 Load coming from the structure is heavy and non uniform.
 Where grillage or raft foundations are either very costly or
their adoption impossible due to local difficulties.
 When it is not possible to maintain foundation trenches in
dry condition by pumping, due to very heavy inflow of
seepage or capillary water.
 When it is not possible to timber the excavation trenches
in the case of deep strip foundation. (strip foundation-
spread footing under wall ).

 When overlay soil is compressible, and water-logged and
firm hard bearing strata is located at quite a large depth.
 When structures are located on river-bed or sea-shore
and foundations are likely to be scoured due to action of
water.
 Large fluctuations in sub-soil water level.
 Canal or deep drainage lines exist near the foundations.
Situations Which Demand Pile Foundations

Types of Piles
 a) Classification based on Function or
Use
 b) Classification based on Materials
 c) Classification based on method of
installation

10
Types of Piles (Based on Use)
1- Sheet Piles
Sheet piling is used primarily to resist lateral pressures such as
flow of water and loose soil. Typical uses include cut-off walls
under dams, cofferdams, trench sheeting, etc.
 Sheet piles are never used to provide vertical support but mostly
used to act as retaining walls. They are used for the following
purposes:
o To construct retaining walls in docks, and other marine works.
o To protect erosion of river banks.
o To retain the sides of foundation trenches.
o To confine the soil to increase its bearing capacity.
o To protect the foundation of structures from erosion by river or sea.
o To isolate foundations from adjacent soils.
Civil engineering practice
CHP # 04: Pile Foundation

15
2- Load Bearing Piles
These are used primarily to transmit loads through soil
formations with poor supporting properties into or onto
formations that are capable of supporting the loads. Depending
upon how load is transferred to the soil, load-bearing piles can
be further classified into:
2(a) End Bearing Piles
If load is transmitted to the soil through the lower tip, the pile is
called an “End Bearing Pile”.
These piles transmit the superimposed load to stronger strata
such as a rock bed. End area of pile times the bearing capacity of
the rock is the total load, which can be applied.

16
Considering reasonable factor of safety, we can find diameter of
the pile required.

End Bearing Piles
ROCK
SOFT SOILPILES

20
2(b) Friction Piles
These are designed to transmit the loads by the frictional force
existing between the sides of the pile and the ground such as the
stuff clays or dense sandy deposit.
Friction can be developed for full length as in first figure or it
can be developed in lower portions only depending upon the
stratification of soil.
Surface area times the safe friction which can be developed per unit
area determines the load to be carried by the pile. Selecting
diameter or length of pile, the other quantity can be calculated.

21
2(b) Friction Piles

Friction Piles
 Skin friction should be carefully evaluated and suitable factor of
safety applied
 The load carrying capacity of friction pile can be increased by-
 increasing diameter of the pile
 increasing the depth of pile
 increasing the number of piles (use as group of piles)
 making surface of the pile rough

28
2(c) End Bearing and Friction Piles
These are the piles that dissipate part of the load by friction and
transfer the remaining load to firm strata.
3- Piles as Soil Compactor
Sometimes closely spaced piles are driven to compact the
surrounding soil.

29
3.0 Types of Piles (Based on material used and method of
construction)
On the basis of the material from which they are made and the
method of constructing and driving them, load-bearing piles
may be classified as follows:
– Timber
a. Untreated
b. Treated with a preservative
– Concrete
a. Pre-cast
b. Cast-in-place
– Steel
a. I-section
b. Steel-pipe
– Composite

30
Driven timber piles, Pacific Highway

DRIVEN PILES(TIMBER, STEEL PIPE PILES)

Fz
Fy
Fx
-My
Mx
Beam seat elevation
Rock
Loose Sand
Applied Loads

40
•Wooden Piles

41
3a Wooden Piles
 These piles, if used below the ground water level, last for a
very long period but ordinarily they last no longer than 30
years or so even if treated.
 The circular piles vary in diameter from 12 inch to 16-inch. If
square sizes are used, they also vary in size fro 12 inch to 16-
inch square. The length of the piles is about 20 times the top
width.
 The timber point may be protected or replaced by a metallic
shoe; shoes are used while driving through soils containing
boulders, gravels, hard clays etc.

42
3a Wooden Piles
 They may be of C.I. and should have sufficient length
of wrought iron straps to connect them with the pile.
 The head of the pile is subjected to a heavy impact of
the driving machine; hence, rings of wrought iron are
fitted to the pile head. They vary in cross-section from
2 in. to 4 in.
 Timber piles should not be loaded above 15 to 20 tons
and should be carefully driven.
 Whenever it is necessary to use a longer pile than
available in usual lengths, it is necessary to splice the
piles together, with their ends abutting each other.

43
3a Wooden Piles
 Additional strength can be obtained by the use of steel
fishplates bolted to the sides of the piles.
Among the advantages of timber piles are the following:
1. The more popular lengths and sizes are available on
short notice.
2. They are economical in cost.
3. They are handled easily, with little danger of breakage.
4. They can be cut off to any desired length after they are
driven.
5. They can be pulled easily in the event removal is
necessary.

44
3a Wooden Piles
Among the disadvantages of timber piles are the following:
1. It may be difficult to obtain piles sufficiently long and
straight for some projects.
2. It may be difficult or impossible to drive them into
hard formations.
3. It is difficult to splice them to increase their lengths.
4. While they are satisfactory when used as friction piles,
they are not suitable for use as end-bearing piles under
heavy loads.
5. The length of life may be short unless the piles are
treated with a preservative.

46
•Concrete Piles

47
3b Concrete Piles
(a) Pre-cast Concrete Piles
 Square and octagonal piles are cast in horizontal forms, while
round piles are casts in vertical forms.
 After the piles are cast, they should be cured for the period
required by specifications, frequently 21 days.
 With the exception of short lengths, Precast concrete piles
must be reinforced with sufficient steel to prevent damage or
breakage while they are being handled from the casting beds to
the driving positions.

48
3b Concrete Piles
Advantages of Pre-cast Concrete Piles
1. High resistance to chemical and biological attacks.
2. High strength.
3. A pipe may be installed along the center of a pile to facilitate
driving.

49
3b Concrete Piles
Disadvantages of Pre-cast Concrete Piles
1. It is difficult to reduce or increase the length.
2. Large sizes require heavy and expensive handling and driving
equipment.
3. Inability to obtain piles by purchase may delay the starting of a
project.
4. Possible breakage of piles during handling or driving produces
a delay hazard.

50
3b Concrete Piles
(b) Cast-in-Place Concrete Piles
 These piles are constructed by depositing the freshly mixed
concrete in place in the ground and letting it cure there. The
two principal methods of constructing such piles are:
1. Driving a metallic shell, leaving it in the ground and filling it
with concrete.
2. Driving a metallic shell and filling it with concrete as the shell
is pulled from the ground.

52
3b Concrete Piles
(b) Advantages of Cast-in-Place Concrete Piles
1. The lightweight shells may be handled and driven easily.
2. Variations in length do not present a serious problem. The
length of a shell may be increased or decreased easily.
3. The shells may be slipped in short lengths and assembled at
the job.
4. Excess reinforcing, to resist stresses caused by handling only,
is eliminated.
5. The danger of breaking a pile while driving is eliminated.
6. Additional piles may be provided quickly if they are needed.

53
3b Concrete Piles
(b) Disadvantages of Cast-in-Place Concrete Piles
1. A slight movement of the earth around an un-reinforced pile
may break it.
2. An uplifting force, acting on the shaft of an uncased and un-
reinforced pile, may cause it to fail in tension.
3. The bottom of pile may not be symmetrical.

54
•Steel Piles

55
3c Steel Piles
 Steel piles may be of I-section or hollow pipe section 10 inches
to 24 inches diameter with 3/8 inches thickness.
 Because of a small sectional area, steel piles are easy to drive.
The pipes are driven with open ends. Compressed air with a
pressure of 100 psi in a 2½ inches or more diameter pipe and
thus facilitates the driving.
 These piles are later on filled with concrete. Steel piles are
mostly used as end bearing piles because of their less available
surface area to take the loads by frictional forces.

56
3c Steel Piles
 In constructing foundations that require piles driven to great
depths, steel I-section probably are more suitable than any
other type.
 Steel piles may be driven through hard materials to a specified
depth to eliminate the danger of failure due to scouring, such
as under a pier in a river.
 Also, steel piles may be driven to great depths through poor
soils to bear on a solid rock stratum.

57
3c Steel Piles
 The great strength of steel combined with the small
displacement of soil permits a large portion of the energy from
a pile hammer to be transmitted to the bottom of a pile.
 As a result, it is possible to drive steel piles into soils, which
could not be penetrated by any other type of pile.
 By weld splicing sections together, lengths in excess of 200ft
have been driven.

59
•Screw Piles

60
Screw Piles
 Screw piles consist of iron or steel shaft
having at its end a cast iron or cast steel
screw, with a blade 1.5ft to 5ft in diameter.
 These piles can be screwed down to a
great depth in clay, etc., and penetrate
through small broken stones.
 The base area of the screw does most of
the weight bearing; they can be used for
bridges in riverbeds with deep clay
foundation.

65
4.0 Pile Driving
The operation of forcing a pile into ground without any
previous excavation is called “Pile Driving”.
Following are the various methods of pile driving:
1. Drop hammer.
2. Steam-hammer.
3. Boring.
4. Screwing.
5. Water jet.

66
4.0 Pile Driving
1- Drop Hammer Method
 It is the simplest method of pile driving. In this method, a
hammer is dropped on the head of the pile and is guided
during its fall by suitable staging.
 The hammer is raised by pulling a rope manually or by steam
engine or electric motor. The weight of the hammer for
driving concrete or wooden piles is about 225 kg for short
piles and 900 kg to 2350 kg for long and heavy piles.
 Hammer is generally dropped from a height of 15m to 45m
and the height is limited to 6 m. The pile-driving frame is kept
in vertical position by suitable ropes.

69
4.0 Pile Driving
2- Steam Hammer Method
 A heavy hammer is dropped on to the pile through a small
height but in quick succession. Single acting or double acting
steam hammers are available.
 These hammers are raised with high-pressure steam and are
dropped under gravity when single acting or by steam where
there is double acting hammer. These hammers are specially
used for driving sheet piles and where small vibrations are
required to be set up in the piles.
 Special devices are used to protect the heads of the piles from
damage due to excessive blows, which they receive.

71
4.0 Pile Driving
3- Boring
 Sometimes, piling is done by boring holes of suitable diameter
to the required depth and then dropping piles in them.
Generally cast-in-situ piles are laid by this method.
4- Screwing
 Screw piles and disc piles are generally driven by this method.
They are driven into the ground by turning them round and
round in one direction with big levers.

73
4.0 Pile Driving
5- Water Jets
 Pile driving can also be done by displacing the material at or
near the foot of the pile by means of one or more water jets
under pressure.
 Sometimes, hammer may be used to force the pile rapidly into
the ground. The pressure of the jet should be sufficient to
displace the soil and other removed materials for driving the
piles quickly and satisfactorily.

75
5.0 Factors Affecting Selection of Piles
Among the factors that will influence the selection of type of
piles for a given project are the following:
1. Type, size, and weight of the structure to be supported.
2. Physical properties of the soil at the site.
3. Depth to a stratum capable of supporting the piles.
4. Possibility of variations in the depth to a supporting stratum.
5. Availability of materials for piles.
6. Number of piles required.
7. Facilities for driving piles.
8. Comparative costs in place.
9. Durability required.
10. Types of structures adjacent to the project.
11. Depth and kind of water, if any, above the ground into which
the piles will be driven.

76
Significance of Pile Foundation
 Pile foundation is suitable for works over water such as bridge`-
piers, foundation of transmission towers and foundation of
multistory buildings.
 From head or cap of piles, we can construct the grids with beams
and columns.
 The number of piles depends on the type of pile and the load
coming from the buildings.

Causes of Failure of Piles
 Load on the pile is more than the designed load.
 Defective workmanship during casting of the pile.
 Displacement of reinforcement during casting.
 Bearing pile resting on a soft strata.
 Improper classification of soil.
 Improper choice of the type of pile.

Causes of Failure of Piles
 Insufficient reinforcement in the pile.
 Decay of timber piles due to attack by insects.
 Buckling of piles due to inadequate lateral support.
 Defective method adopted for driving the pile.
 Incorrect assessment of the bearing capacity of the pile.
 Lateral forces not considered in the design of piles.

Pile Foundation Types and Uses in Civil Engineering Projects

Empfohlen

Empfohlen

Weitere ähnliche Inhalte

Was ist angesagt?

Was ist angesagt? (20)

Andere mochten auch

Andere mochten auch (20)

Ähnlich wie Pile Foundation Types and Uses in Civil Engineering Projects

Ähnlich wie Pile Foundation Types and Uses in Civil Engineering Projects (20)

Kürzlich hochgeladen

Kürzlich hochgeladen (20)

Pile Foundation Types and Uses in Civil Engineering Projects