When is a pile foundation typically used?

• A. A shallow foundation is preferred over a deep foundation
• B. When the soil is weak or problematic
• C. Only for light structures
• D. In areas with high seismic activity

Answer: (B)

A pile foundation is typically used when the soil conditions are weak or problematic. This type of foundation is designed to transfer the load of a structure to deeper, more stable soil or bedrock layers that can adequately support the weight of the building. In situations where the upper layers of soil are not competent enough to handle the loads imposed by a structure—such as in clay, loose sand, or filled ground—a pile foundation becomes necessary to prevent issues like settlement, tilting, or even failure of the structure.

The use of pile foundations is especially appealing in locations where the upper soil layer cannot sustain the loads of heavy constructions, such as tall buildings, bridges, or industrial facilities. Pile foundations can reach down to more stable soil or rock layers, ensuring the overall stability and integrity of the structure.

In contrast, a shallow foundation would usually be preferred in scenarios where the near-surface conditions are conducive to load-bearing. While seismic activity can influence the choice of foundation type, it is not the primary reason for selecting a pile foundation. Furthermore, pile foundations can support both light and heavy structures, making the suggestion that they are only for light structures incorrect.