Collapsible soil is one of the problematic soils in geotechnical engineering. They are known for their strength when they are dry and their sudden and excessive loss of volume when they are inundated.
The present study presents the results of experimental investigations on passive earth pressure acting on walls retaining dry and wet collapsible soils. The objective of these investigations was to study the effect of inundation due to the rise of the ground water table on the earth pressure. Lab Tests were carried out on a prototype set-up which was developed to simulate the movement of a retaining wall towards the collapsible backfill, meaning the passive pressure state. The experiments were conducted on collapsible soil with various collapse potentials to study this variation effect on the results. 
The results of the experimental investigation were used to validate the results of the numerical model developed in this investigation. The numerical model was used to generate results for a wide range of parameters, which believe to govern this complex soil.