Definition of foundation: The bottom most part of the substructure which transmit load of the structure along with its own weight into the soil underneath or surroundings
without carrying shear failure or bearing capacity failure and excessive settlement.
Foundations can be further classified as shallow and deep. This classification depends on the depth of load transfer from structure to the ground. Different publications define shallow foundation and its definition varies. According to BS 8004, foundations of arbitrary embedment depth of 3 meter are considered as shallow foundations.
According to Terzaghi, When the depth to the bottom of foundation is less than or equal to its least dimension, then the foundation will be called as shallow foundation.
Deep foundation may be defined as the piles installed at depths. Piles may be pre manufactured and driven into ground by jacking. Or these are cast in place in a shaft formed in the ground by excavation or boring.
Purpose of Foundation:
The main purpose of the foundation is is to distribute the structural load over a large bearing area without causing bearing capacity failure and excessive settlement to obtain a level and hard strata or bed for building operations to increase the stability of the structure as a whole.