Civil Engineering - UPSC Civil Service Exam Questions - Discussion

Historically, sands were considered to be the only type of soil susceptible to liquefaction, but liquefaction has also been observed in gravel and silt.

Liquefaction occurs in dense saturated or submerged sands. Even though the dense sands are strong under normal circumstances, under earthquake loads, the vibration causes foundations to sink in the sands thereby causing the sands to act as if they are liquid. Hence it is called liquefaction.