The foundation is the part of the structure that is in direct contact with the ground. It is the part of the structure that transfers the weight of the structure to the ground. The foundation is therefore an integral link between the structure proper and the earth supporting it. The foundation transfers the load of the structure over a large area to the underlying soil. It prevents segregation by uniformly loading the substrata. Foundations are usually made of bricks, stones, concrete, steel etc. The choice of material and type of foundation depends on the type of superstructure and subsoil.
Foundation design must take into account the effects of construction on the environment, such as pile driving vibration, pumping and discharge of groundwater, the disposal of waste materials and operation of heavy mechanical plants. Foundations must be durable to resist the attack of harmful substances.
A foundation is designed such that:
- The soil below does not fail in shear.
- The settlement is within a safe limit.
The pressure that the soil can safely withstand is known as the ‘allowable bearing pressure’.
Foundations may be broadly classified into two categories.
- Shallow foundation: A shallow foundation transmits the load to the strata at a shallow depth.
- Deep foundation: A deep foundation transmits the load at a considerable depth below the ground surface.
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