Floating raft system
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Floating raft is type of land-based foundation that protects against settlement and the liquefaction of soft soil due to seismic activity. It was a necessary innovation in the development of tall buildings in the wet soil of Chicago in the 19th century, where it was developed by John Wellborn Root who came up with the idea of interlacing the concrete slab with steel beams.
For a floating raft foundation, or floating foundation, the foundation has a volume such that, were that volume filled with soil, it would be equal in weight to the total weight of the structure. When the soil is so soft that not even friction piles will support the building load, the final option is the use of a floating foundation, making the building like a boat that obeys Archimedes’ principle; it is buoyed up by the weight of the earth displaced in creating the foundation.