Question

what do you mean by liquefaction discuss different ways by which liquefaction be achieved

Answer 1

In materials science, liquefaction is a process that generates a liquid from a solid or a gas or that generates a non-liquid phase which behaves in accordance with fluid dynamics. It occurs both naturally and artificially. As an example of the latter, a "major commercial application of liquefaction is the liquefaction of air to allow separation of the constituents, such as oxygen, nitrogen, and the noble gases." Another is the conversion of solid coal into a liquid form usable as a substitute for liquid fuels.  

There are two main types of liquefaction (Coduto, 1999):
Flow Liquefaction occurs in loose saturated sands and generally leads to sudden large shear movements. Cyclic Mobility occurs in medium to dense saturated sands, the shear movements in this type of liquefaction are not generally as dramatic as flow liquefaction as cyclic mobility produces incremental shear movements.