Question

How do you define a shallow foundation in term of the foundation depth? Can we state that the long-term settlement and the short-term settlement of a foundation constructed on a sandy layer are almost the same? Please briefly justify your answer.

Answer 1

As per terzaghi a foundation is said to be shallow foundation if its depth is equal to or less than its width i .e { Df / B } ratio is less than or equal to 1. Whereas according to skempton a shallow foundation is the one having { Df/ B } ratio less than or equal to 2.5.

Yes the long term and short term settlement of a foundation constructed on sandy soil is same as sandy soil doesn't not take much time for consolidation i.e pore water dissipation. It dissipate all the pore water quickly so the consolidation settlement occurrs as soon as the foundation is constructed. However in case of clay the consolidation is a time taking process so for foundation on clayey soil long term settlement is more than short term settlement.

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