The correct answer is D. All the above.
Pile foundations are used when the soil is compressible, water logged, or made up of a mixture of both. Compressible soil is soil that can be easily compressed under pressure. This can cause the foundation of a building to sink, which can lead to structural damage. Water logged soil is soil that is saturated with water. This can make the soil unstable and can also lead to the foundation of a building sinking. Soil that is made up of a mixture of compressible and water logged soil is the most difficult type of soil to build on. In these cases, pile foundations are often the only option.
Pile foundations are columns that are driven into the ground. The weight of the building is transferred to the piles, which then transfer the weight to the underlying bedrock. This type of foundation is very strong and can support even the heaviest buildings.
Pile foundations are a complex and expensive type of foundation. However, they are often the only option for building on compressible or water logged soil. If you are considering building on a site with these types of soils, it is important to consult with a structural engineer to determine if pile foundations are the right choice for your project.