Floating raft system
Encyclopedia
Floating raft is type of land-based foundation
Foundation (architecture)
A foundation is the lowest and supporting layer of a structure. Foundations are generally divided into two categories: shallow foundations and deep foundations.-Shallow foundations:...

 that protects against settlement and the liquefaction
Soil liquefaction
Soil liquefaction describes a phenomenon whereby a saturated soil substantially loses strength and stiffness in response to an applied stress, usually earthquake shaking or other sudden change in stress condition, causing it to behave like a liquid....

 of soft soil due to seismic activity. It was a necessary innovation in the development of tall buildings in the wet soil of Chicago
Chicago
Chicago is the largest city in the US state of Illinois. With nearly 2.7 million residents, it is the most populous city in the Midwestern United States and the third most populous in the US, after New York City and Los Angeles...

 in the 19th century, where it was developed by John Wellborn Root
John Wellborn Root
John Wellborn Root was an American architect who worked out of Chicago with Daniel Burnham. He was one of the founders of the Chicago School style...

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 even friction piles will not 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.
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