Situations which may necessitate the use of piles are :

1. Where insufficient load bearing capacity is offered by the soil at a shallow depth , but sufficient is available at a greater depth
2. Where the nature of the soil at a shallow depth is variable and performance is upredictable , such as in areas of filled land.
3. Where soils at shallow depths are subject to shrinkage or swelling due to seasonal changes .
4. Where buildings are subjected to an uplifting force , and require to be anchored to the ground

Pile foundations may be classified in 2 ways:

1. By the way in whch they are installed
2. BY the way in which they transfer their loads to the ground