Piles are often pipe but not always and are generally driven or inserted into the ground until stable soil is found. These are called end load or bearing piles.
Where there is no solid soil within a reasonable distance from the surface, friction piles can be used. The difference is that friction piles transfer the load thru contact with the surrounding soil and so are subject to vertical movement under some conditions.
Engineers spend a lot to time in making these calculations to insure a successful project.
- A concrete slab, which is said to “float” on the ground, and will sink into the ground as the building is constructed on it, and the load increases, reaching a calculated equilibrium and stability.
- Piles, either metal, cast in-situ or pre-cast, that extend down to rock beneath soft ground.
- Friction piles, which penetrate the soft ground, to the extent that friction around their perimeter is high enough to resist movement due to loading.
In any case, the objective is to transmit loads from and through the building, to a stable base in the ground.