CE-200
Details of Construction
Deep Foundation
DEFINITION
1. Deep Foundations are those
in which the depth of the foundation is very large in
comparison to its width.
When Used?
In cases where
The strata of good bearing capacity is not available near the ground.
In these cases the foundation of the structure has to be taken
deep with the purpose of attaining a bearing stratum which is
suitable and which ensures stability and durability of a structure.
The bearing stratum is not the only case. There may be many
other cases. For example, the foundation for a bridge pier must
be placed below the scour depth, although suitable bearing
stratum may exist at a higher level.
Forms of Construction
Most common forms of construction pertaining to deep
foundations are:
Pile Foundation (more commonly used in building construction)
Cofferdams
Caisson or Well Foundation
Pile Foundation
PILE BENEATH STRUCTURE
Pile Foundations
Where Used :
stratum of required bearing capacity is at greater depth
sub-soil water table is so high that it can easily affect the other
foundations
large fluctuations in sub-soil water level
when it is not possible to maintain foundation trenches in dry condition by
pumping, due to very heavy inflow of seepage or capillary water.
where raft foundations are either very costly or their adoption impossible
due to local difficulties
when structures are located on river-bed or sea-shore and foundations are
likely to be scoured due to action of water.
Advantages:
Provides a common solution to all difficult foundation site problems
Can be used for any type of structure and in any type of soil
Types of Piles Based on Function
a) Classification based on Function or Use
1. Bearing Piles or End Bearing Piles
2. Friction Piles or Skin Friction Piles
3. Sheet Piles
4. Tension Piles or Uplift Piles
5. Anchor Piles
6. Batter Piles
7. Fender Piles
8. Compaction Piles
Types of Piles Based on Function
(contd)
Bearing Piles
Driven into the ground until a hard stratum is reached.
Acts as pillars supporting the super-structure and transmitting
the load to the ground.
Piles, by themselves do not support the load, rather acts as a
medium to transmit the load from the foundation to the
resisting sub-stratum.
Types of Piles Based on Function
(contd)
Friction Piles (Floating Piles)
Piles are driven at a site where soil is weak or soft to a considerable depth
and it is not economical or rather possible to rest the bottom end of the pile
on the hard stratum.
Load is carried by the friction developed between the sides of the pile and
the surrounding ground ( skin friction).
The piles are driven up to such a depth that skin friction developed at the
sides of the piles equals the load coming on the piles.
Skin friction should be carefully evaluated and suitable factor of safety
applied, as it is this which is supporting the whole of structure over its head.
The load carrying capacity of friction pile can be increased by-
increasing diameter of the pile
driving the pile for larger depth
making surface of the pile rough
Types of Piles Based on Function
(contd)
Types of Piles based on Function
(contd)
Types of Piles Based on Function
(contd)
Sheet Piles
Sheet piles are never used to provide vertical support but mostly
used to act as retaining walls. They are used for the following
purposes:
To construct retaining walls in docks, and other marine works.
To protect erosion of river banks.
To retain the sides of foundation trenches.
To confine the soil to increase its bearing capacity.
To protect the foundation of structures from erosion by river or
sea.
To isolate foundations from adjacent soils.
Types of Piles Based on Function
(contd)
Figure: Sheet Piles
Types of Piles Based on Function
(contd)
Anchor Piles
Piles are used to provide anchorage against horizontal pull from sheet piling
wall or other pulling forces.
Batter piles:
Piles are driven at an inclination to resist large horizontal and inclined forces.
Fender piles:
Piles are used to protect concrete deck or other water front structures from the
abrasion or impact caused from the ships or barges.
Ordinarily made up of timber.
Compaction piles:
When piles are driven in granular soil with the aim of increasing the bearing
capacity of the soil, the piles are termed as compaction piles.
Types of Piles Based on Function
(contd)
Types of Piles Based on
Materials
a) Classification based on Materials
1. Timber Piles
2. Concrete Piles
3. Steel Piles
4. Composite Piles
Timber Piles
• Economical to support light
structure.
• To facilitate driving, the
lower end is pointed and
provided with a cast iron
conical shoe.
• Piles are subjected to decay
for alternate dry and wet
condition (on account of
variation of ground water
level), especially if not
properly treated
Concrete Piles
Concrete Piles are of 2 types:
Pre-cast Piles
Cast in situ Piles
Pre-cast Piles
• Piles of any size are made in advance and then
used at the site
Cast-in-situ Piles
• Non-displacement pile in which a hole of the specified
diametre is bored to the required depth.
• Cast with concrete of specified strength after the
reinforcement is placed into the hole.
Steel Piles
• Can be driven in very
long lengths
• Liable to corrosion
above the soil line
• More expensive than
timber or concrete
Composite Piles
• Combinations of
materials are
used.
• Most common
materials are
steel and
concrete.
Pile Cap
• It is a thick concrete mat that rests on driven concrete or
timber piles.
• Provides stability to the foundation in soft and unstable
ground
• It distributes the load of the building into the piles.
Pile Cap
Pile cap for Pile cap for Pile cap for
two piles three piles four piles
Pile Driving
I. By Drop Hammer.
II. By Steam Hammer.
III. By Water Jets (Wash Boring ).
IV. By Boring (Auger Boring).
Drop Hammer
• Hammer is raised by a rope or a steel cable
• Then it is allowed to drop on pile cap
• Weight of drop depends on the shape and length
of pile and the nature of the ground
• Takes a lot of time
Steam Hammer
• Hammer is automatically raised and dropped.
• A steam cylinder and piston is used.
• Steam pressure and the rate of hammer blow
are kept uniform.
Wash Boring
• Wash boring is a fast and simple method for advancing holes in soft
to stiff cohesive soils and fine sand. Boulders and rock can not be
penetrated by this method.
• The method consists of first driving a hollow steel pipe known as
casing pipe/drive pipe in to the ground.
• Through this casing pipe, a hollow drilled rod with a sharp chisel or
chopping bit at the lower end known as water jet pipe or wash pipe is
inserted.
• Upper end of wash pipe is connected to water pump and lower end is
contracted to produce get action.
Wash Boring (contd)
• Water is forced under pressure through the drill rod which is
alternatively raised and dropped, and also rotated. The resulting
chopping and getting action of the bit and water disintegrates the
soil.
• The cuttings are forced up to the ground surface in the form of soil-
water slurry through the annular space between the drill rod and the
casing.
• The slurry is collected and samples of materials are obtained by
settlement.
Boring
Can penetrate beds of hard soil or soft rock
Augur or Rotary Drilling can be used.
Precast and In-situ piles may be used.
Procedure for Pile driving
Tripod Placing
Tripod
Auger Placement
Components of Auger
Mass Rod
Hose Pipe
Cutter
Procedure of Pile Casting
Preparation of the House
Drawing water
From the house
Mud from To the bore hole
the bore Using a pump
hole
Tank connected
To the Hose pipe
Connecting Auger to the Rig
Hooking the auger to Connecting the hose pipe
the rope of the rig to the auger
Centering
Centering the Auger by moving the Rig
Boring
Mud coming out of the bore hole
Driving the Casing
Boring through the Casing
Connecting the Drilling Rod
Hooking the Drilling Rod Connecting the Hose pipe to
with the rope of the Rig the Drilling Rod
Connecting the Drilling Rod
Joining the
Drilling Rod to the
head of the Auger
by Threading
Boring with the Drilling Rod
Bringing out the Drilling Rod
Preparation of the Reinforcement
Spiral reinforcement bars are driven into
the straight bars
Preparation of the Reinforcement
straight
bars spiral bars
Preparation of the Reinforcement
Spiral bars are joined with the straight The bars are welded for extra
bars with wires. strength.
Rebar Placement
Driving the Reinforcement
Reinforcement bars are welded at the
joints
Setting up the Tremie Pipe
Joining by threading Clamping the Tremie Pipe
Setting up the Funnel
Concrete Casting
Tremie Pipe
Concrete falling
Into the bore hole
From the bucket
Through the funnel
Concrete
Pile Caps
Cofferdams
Cofferdams may be defined as a temporary structure constructed in a
river or a lake or any other water bearing surface for excluding water
form a given site to enable the building operation to be performed on
dry surface.
Cofferdams may be divided into the following category based on the
materials used during construction:
Earthier cofferdam.
Rock fill cofferdam.
Single-walled cofferdam.
Double-walled cofferdam.
Crib V
Cellular cofferdam.(Circular or diaphragm type)
Caissons
Caissons are water light structures made up of wood, steel or
reinforced concrete, constructed in connection with excavation for
foundations of bridges, piers, abutments in river and lake dock
structure fore shore protection etc.
The caisson remains in its pose and ultimately becomes as integral
parts of the permanent structure.
Caisson can be broadly classified into the following three types:
Open Caisson
Box Caisson (Floating Caisson)
Pneumatic Caisson
Padma Bridge Pier (Source-internet)
ASSIGNMENT
• State the different types of deep
foundations you recommend under
different situations and soils.
