The most dangerous factor for collapsible soils is the time the collapse process takes, which is a very short time, but this time is found to be related to the initial degree of saturation, and this time becomes longer with the reduction of the initial degree of saturation. Few days or even few hours may be significant in the salvage of properties or even persons from direct danger that may occur if dry collapsible soil are subjected to water, either from precipitation from the top, or from rising water table from the bottom.