TYPES OF FOUNDATION AND ITS DETAILS

TYPES OF FOUNDATION AND ITS DETAILS



Foundation is the lowest part of the structure .it is used to transmit the load from structure to hard strata of the soil.
The foundation is classified into two types
1.shallow foundation
2.deep foundation

SHALLOW FOUNDATION

When the load is transferred through the shear resistance of the bearing stratum and the depth not more than 3m is called shallow foundation
The depth of the foundation less than or equal to the width of the foundation is also called shallow foundation.

DEEP FOUNDATION

Depth of foundation is more than 3m is called deep foundation. the load is transferred to the load bearing stratum by mean of friction or end bearings. Heavy load buildings are used deep foundation for like multi storied buildings, dams , docks etc.

DETAILS OF DIFFERENT TYPES OF FOUNDATIONS


SHALLOW FOUNDATION

We are already discussed about the shallow foundation .now we are going to see types of shallow foundations and its uses.

ISOLATED FOOTINGS

In framed structures where several columns involved can be provided with masonry or concrete footing. If masonry footing is provided steps are given and the foundations are is thus increased so that the stresses developed at the base is within the limit. Concrete can be molded to any shape and hence a concrete footing may be a sloping one to provide sufficient spread. In case masonry footing the projection of each step must be ½ brick thick and each step is made of 1 or 2 bricks put together.

COMBINED FOOTING

This type of footing is provided when the space between two columns is very small and overlap single footing to another footing combined footing is provided. This foundation is rectangular or trapezoidal shape.
STRIPE FOOTING

Stripe footing is the one of the shallow foundation .this foundation is used when the required bearing capacity of soil is available less than the 3m from the ground level. There the footing is provide the length of the wall in case of load bearing walls. They are classified into two types
       I.          Simple footing
     II.          Stepped footing

SIMPLE FOOTING

Simple footing is provided for the very  light load structure like residential buildings.in this footing foundation is used cement concrete or lime concrete. The projection of both side is 15 cm.


STEPPED FOOTING

Stepped footing is provided when the ground level has a slope. Otherwise it not provided because it is not economical. Two or three footings are provided below the ground level. This footings are constructed in brick masonry.

RAFT OF MAT FOUNDATION

Raft foundation is provided when a combined footing covers a number of columns in a row or a number of wall in a number of rows it is than termed as a raft or mat foundation. Raft foundation transmits the load to the slab through the continuous slab. This type of foundation is used where the soil have low bearing capacity and un uniform settlement. Such a foundation is used heavy load structures.

DEEP FOUNDATION

Deep foundation is provide where the bearing capacity of soil is not available within the 3m deep from earth surface. Also heavy loaded structures like multi storied buildings.

PILE FOUNDATION

Pile foundation is the one of the deep foundation. This foundation is laid under the following conditions.
1.when the structure is tall and heavy and the soil is loose or sandy and firm ground is available only at 10-15m depth
2. when the foundation to be laid is below the scour the scour depth
3.when excessive settlement is to be avoided.

PILE FOUNDATIONS ARE CLASSIFIED INTO THREE TYPES
       I.          Bearing piles
     II.          Fiction files
    III.          Combined bearing and friction piles

BEARING PILES

These piles are transmitted the load to the hard strata of soil by the way of the resistance developed at the pile base. This type of foundation is adopted when the soil above the hard stratum is not suitable to bearing the load. bearing piles are designed as columns .

FRICTION PILES

These piles not transmit the load to end of the pile .this also called floating pile. The load is resisted by the way of friction between the file to the soil. And its provided when the soil is sandy to a large depth.

COMBINED BEARING AND FRICTION PILES

When the soil is sandy to a limited depth after which there is hard stratum then the foundation used is a combined bearing and friction pile.

There are many piles are provided below the columns .the pile cap is provided at the top of the pile . the pile cap is used to transmit the load from the columns to the piles equally.


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