Transcript of "Deep foundation ppt my final tos work"
A foundation is the lowest and supporting layer of a structure.
Foundations are generally divided into two categories:
According to terzaghi , a
foundation is shallow if its
depth is equal to or less
than its width. In case of
deep foundation the
depth is equal to or
greater than its width
There are a variety of shallow foundation types used in the construction of
Combined or Cantilevered
Slab on grade
Deep foundation are those foundation in which the depth of the foundation is
very large in comparison to its width.
Types of deep foundation
Deep strip,rectangular and square footing.
Pier foundation or drilled caissan foundation.
Well foundation or caissan.
Cassion or well foundation
TYPES OF PILES
piles may be classified as follows :
classification based on function
classification based on material
CLASSIFICATION BASED ON FUNCTION :
based on the function or the use piles may be classified:
end bearing pile ( they are used transfer load through water or soft soil to
suitable bearing stratum.)
tension or uplift piles
END BEARING PILES
If the loads is transferred through soft soil
or water to a suitable bearing stratum by
means of end bearing piles it is known as
end bearing piles and point piles
END BEARING PILES
If the loads is transferred to a depth of
the relatively weak soil by meansof
friction along the length of the piles it
is known as friction piles.
Piles are also used for compacting loose granular deposite these piles are
short and are as known as compaction piles
Sometimes piles are used to resist upward forces these piles are
subjected to tension are known as tension piles
In case of large lateral loads or inclined forces,piles driven at an angle
resist forces effectively these are called batter piles
CLASSIFICATION BASED ON MATERIAL S AND COMPOSITION
pre – cast
cast in situ
driven piles (uncased or cased )
bored piles (pressure piles,underReamed piles.
concrete and timber
concrete and steel
PRE CAST CONCRETE PILES
CAST IN PLACE PILES
These are made by making a hole in the ground and filing it with
In cased piles , a thin metal shell or casing is first driven in the ground
which is then filled with concrete .
In uncased piles , a metal casing is first driven in the ground ,which is
gradually withdrawn as the concreting is done
These piles are most commonly used where excessive shrinkage andd swelling of
clays out the use of shallow spread footing. The usual size of under –reamed piles
is 150-250mm dia and 3000-4000mm long. The dia of the under –reamed portion is
2 to3 times the dia of the shaft.
TYPES OF PILES
MINIMUM PILE SPACING
( centre to centre distance)
3d where d is the diameter of circumscr
- bing circle for non –circular section
or 900mm which ever is more
end –bearing piles
passing though relatively compressible
2.5d or 750mm whichever is more
End bearing piles passing through
compressible strata and resting in stiff -3.5d or 1050mm which ever is more
end bearing piles on rock
- 2d or 1.75x diagonal dim of pile of noncircular
sect ion or 600mm whichever is more
- 2d or 600 mm whichever is more
TYPES OF PILE CHOSEN DEPENDS
ON FOLLOWING FACTORS:
What type of pile is readily available
Location & type of structure (magnitude of loading)
Ground Condition (soil type)
TYPES OF PILE CONSTRUCTION
- It cause the soil to be displaced radially as well as vertically as
pile shaft is driven or jacked into the ground.
Non Displacement Piles
- It cause the soil to be removed and the resulting hole filled with
concrete or a pre cast concrete pile is dropped into the hole and
DISPLACEMENT PILE METHOD
NON -DISPLACEMENT PILE METHOD
It’s a vertical bridge support.
It’s a foundation for carrying a heavy
structural load which is constructed in site
in a deep excavation.
CONSTRUCTING THE PIERS FRAMINGConstructing
POST FOOTING AND DETAILS
RAMP IS INSTALLED
FLOOR DECKING INSTALLATION
RAMP IS BOLTED
COMPLETE PIERS FRAMES
It’s a prefabricated hollow box or cylinder.
It is sunk into the ground to some desired depth and then filled
with concrete thus forming a foundation.
Most often used in the construction of bridge piers & other
structures that require foundation beneath rivers & other bodies of
TYPES OF WELL FOUNDATION OR CASSION
Caisson As One Of The Elements In This Structure
METHOD OF INSTALLATION
Dropping Weight or Drop Hammers
commonly used method of insertion of displacement piles
Most suitable to drive pile in non cohesive granular soil
Vibratory Hammers or vibratory method of pile driving
very effective in driving piles through non cohesive granular soil
Jacking Method Of Insertion
Rapid controlled explosions can be produced by the diesel hammer.
The explosions raise a ram which is used to drive the pile into the ground.
Although the ram is smaller than the weight used in the drop hammer the
increased frequency of the blows can make up for this inefficiency.
This type of hammer is most suitable for driving piles through non-cohesive
granular soils where the majority of the resistance is from end bearing.
Vibratory Method of Pile Driving
Vibratory methods can prove to be very effective in driving piles through non
cohesive granular soils.
The vibration of the pile excites the soil grains adjacent to the pile making the soil
almost free flowing thus significantly reducing friction along the pile shaft.
However the large energy resulting from the vibrations can damage equipment,
noise and vibration propagation can also result in the settlement of nearby buildings.
Pile Driving Rig - raise and temporarily
support the pile that being driven and to
support the pile hammer.
Dropping Weight / Drop Hammers
A weight approximately half that of the pile is raised a suitable distance in a
guide and released to strike the pile head.
When driving a hollow pile tube the weight usually acts on a plug at the
bottom of the pile thus reducing any excess stresses along the length of the
tube during insertion.
Jacking Method Of Insertion
Jacked Piles are most commonly used in underpinning structures
By excavating underneath a structure short lengths of pile can be
inserted and jacked into the ground using the underside of the existing
structure as a reaction.
DR .B.C PUNMIA
S N SINHA