Laboratory investigation of the effect of cyclic wetting and drying on the behaviour of an expansive soil

The behaviour of an expansive soil was studied through a number of experiments involving cycles of wetting and drying. Laboratory tests were conducted on compacted samples of an expansive soil (a mixture of bentonite and kaolin, CH) in a modified oedometer under different constant surcharge pressures. The void ratio and water content of samples were determined at different stages. The results show that the swelling–shrinkage was reversible after the soil reached the equilibrium condition where the deformations were the same and the wetting and drying paths (in the water content–void ratio space) converged to an S-shaped curve. The hysteresis phenomenon was studied through the variation of the void ratio with suction, and the results showed that it diminished gradually with the increase in cycles of wetting and drying. The effect of fabric on the behaviour of soil samples was studied during cycles of wetting and drying. The results show that the samples with lower initial water content (on the dry side of optimum) have more swelling potential than samples with a higher initial water content (on the wet side of optimum).