Foundation (engineering)
A foundation is the element of a structure which connects it to the ground, and transfers loads from the structure to the ground. Foundations are generally considered either shallow or deep. Foundation engineering is the application of soil mechanics and rock mechanics (Geotechnical engineering) in the design of foundation elements of structures.
Floating raft system
When the soil is so soft that not even friction piles will support the building load, these types of foundation are the final option and makes the building behave like a boat: obeying Archimedes' principle, buoyed up by the weight of the earth displaced in creating the foundation.