Foundation is often referred to as a substructure of a building. Foundation transfers the load coming from the superstructure safely to the beneath soil.
We can classify foundation in two broader types-
- Shallow foundation
- Deep foundation
It is one, in which the breadth to depth ratio is more than two. Shallow foundations are suitable where loads coming from the structure is less or it is also preferable where firm ground strata are available at shallow depth.
The following are some types of the shallow foundation.
- Isolated column footing: It is used under a single column. The shape of the column may be circular, square, rectangular or even complex like ‘L’ shaped or ‘T’ shaped. There are two subtypes of this type of footing.
- Sloped footing: This type, footing got battered shape.
- Step footing: This type, footing resembles the shape of steps.
- Combined footing: This type of footing is adopted when there is one column near the property line or it may be adopted when the two columns are very near to each other such that separate footing is not possible.
It could also be subdivided into two types.
- Rectangular combined footing
- Trapezoidal combined footing
- Raft foundation: This type of foundation is also known as mat foundation and these are suitable in case black cotton soil.
- Steel grillage footing: This type of foundation is most suited for steel columns.
As per Coulomb, if for a foundation the depth to breadth ratio exceeds 2, then it may be classified as deep footing.
When firm ground strata are not available at shallow depth, the engineer may need to go deep in the ground to place the foundation.
Following are the types of deep foundation
- Pile foundation: Pile foundation is used where loading from the superstructure is very heavy or beneath soil has a poor bearing capacity. There are many types of pile foundations. You can get details about the pile foundation here types of pile foundation
- Well foundation: This type of foundation is adopted for bridges. This type of footing is also known as caissons.