Foundation:-
Foundation is the lowest portion of a structure which transmits the load into the supporting soil. The main purpose of the foundation is to distribute the total weight of the superstructure over a large area of soil.
Classification of Foundation
- Shallow Foundation
- Deep Foundation
SHALLOW FOUNDATION:-
Depth Of Foundation Less Or Equal To Width
Types Of Shallow Foundation
- Spread Footing
- Combined Footing
- Grillage Footing
- Raft Foundation
Spread or Isolated Footing:-
A spread footing (or isolated or pad) footing is provided to support an individual column. A spread footing is a circular, square or rectangular slab of uniform thickness. Sometimes, it is stepped or haunched to spread the load over a large area.
these are some spread foundation
Combined Footing:
A common footing provided for two or more columns is known as a combined footing. This type of construction becomes useful when an exterior column situated near the boundary line of the plot and it is not possible to project its footing symmetrically on both the sides.
Rectangular & trapezoidal Combine Footing
Mat or Raft Foundations:
This method of increasing the bearing power of soil becomes very useful when the load coming on the soil is practically uniform, while the soil is of yielding natural. (e.g. soft clay or reclaimed soil).
the method consists of providing an R.C.C slab of suitable thickness and with necessary reinforcement. the raft is designed in such a way that the allowable bearing power of the soil is not exceeded. if required, beam and slab construction in R.C.C can be also carried out.
Grillage Foundation
In this method, the depth is limited to 1m to 1.5m and the width is increased considerably to bring the pressure on the soil within the permissible limits. the superstructure rests on two perpendicular tiers of R.S.J. grillage foundation for a steel stanchion and a wall respectively.
Inverted Arches Foundation
The method consists in constructing the inverted arches between the piers. the rise of the inverted arch is about 1/5to 1/10 of the span and the inverted arch is invariably built in half-brick rings.
Deep Foundation:-
Depth Of Foundation Greater than width It’s Called Deep Foundation
Types Of Deep Foundation
The piles are broadly classified into the following two categories
- Load Bearing Piles
- Non-load Bearing Piles
Load Bearing Piles
These piles bear the load coming from the structure. the piles are generally driven vertically or in near vertical position. when a horizontal force is to be resisted, the piles may be driven in an inclined position and such inclined piles are termed as the batter piles.
- Bearing Piles:-
- These piles penetrate through the soft soil and their bottoms rest on a hard bed. thus, they end bearing pile and act as columns or piers. the soft ground through which the pier pass also gives some lateral support and thus increase the load carrying capacity of the bearing piles.
- Friction Piles:
When loose soil extends to a great depth, the piles are driven up to such a depth that's the frictional resistance developed at the sides of the piles equals the load coming on the piles. great care taken should be taken to determine the frictional resistance offered by the soil and suitable factor of safety should be provided in the design.
The total frictional resistance can be increased in the following ways.
- By increasing the diameter of the pile.
- By driving the pile to a greater depth.
- By making the surface of pile rough.
- By placing the pile closely.
- By grouping the piles.
Non-load bearing piles
These piles are used to function as the separating members below ground level and they are generally not designed to take any vertical load. however such piles are indeed to be designed to carry the horizontal earth pressure.Concrete Sheet Piles:-
These piles are always pre-cast and the reinforcement is provided as per design. the piles are square or rectangular in cross section and they are driven side by side so as to form a continuous wall. the width of pre-cast R.C.C. piles varies from 500mm to 600mm and the thickness varies from 20mm to 60mm.the reinforcement is in the form of vertical bars and hoops.
Steel Sheet Piles:-
The steel sheet piles are now commonly used. the various patented forms have been developed for the steel sheet piles. they are generally made from steel sheets 200mm to 300mm wide and 4m to 5m long with suitable interlocking arrangments so as to form fairly watertight joints.
Timber Sheet Piles:-
The wooden sheet piles are commonly used for the temporary works such as cofferdams.they usually consist of wooden boards 80mm to 150mm thick, 200mm to 300mm wide and 2 meters to 4 meters long.
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