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 prevent frost damage. For such foundations as bridge piers, the depth of the foundation must be sufficient to prevent undermining by scour.
2. Bearing capacity failure
The foundation must be safe against a bearing capacity failure.
The foundation must not settle to such an extent that it damages the structure.
The foundation must be of adequate quality so that it is not subjected to deterioration, such as from sulfate 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 could expand or shrink causing movement of the foundation and damage to the structure.
7. Seismic forces
The foundation must be able to support the structure during an earthquake without 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.