Selection of Type of Foundation

The selection of a particular type of foundation is often based on a number of factors, such as:

1.Adequate depth

The foundation must have an adequate depth to preventfrost damage. For such foundations as bridge piers, the depth of the foundation must be sufficient to preventundermining by scour.

2.Bearing capacity failure

The foundation must be safe against abearing capacity failure.

3.Settlement

The foundationmust not settleto such an extent that it damages the structure.

4.Quality

The foundation must be of adequate quality so that it is not subjected to deterioration, such as fromsulfate attack.

5.Adequate strength

The foundation must be designed with sufficient strength that it does not fracture or break apart under the applied superstructure loads. The foundation must also be properly constructed in conformance with the design specifications.

6.Adverse soil changes

The foundation must be able to resist long-term adverse soil changes. An example is expansive soil, which couldexpand or shrinkcausing movement of the foundation and damage to the structure.

7.Seismic forces

The foundation must be able to support the structure during anearthquakewithout excessive settlement or lateral movement.

Based on an analysis of all of the factors listed above, a specific type of foundation (i.e., shallow versus deep) would be recommended by the geotechnical engineer.

The image given below can be used as a guide for selection of an appropriate type of foundation based on different soil conditions.