The influence of suction changes on collapsibility and volume change behavior of unsaturated clay soil

Lack of consideration in unsaturated soils behaviors namely volume change and collapse have caused lots of damages to foundations, buildings, and other structures. Such behaviors are related to drying and wetting phenomena. This paper presents results from triaxial tests on unsaturated clayey soil of Yasouj subjected to drying and wetting cycles using a modified triaxial equipment. Various levels of matric suction ( − ) and net normal stress ( − ) were applied on the unsaturated specimens. The results indicated that under a similar stress level, the void ratios of samples under suction were significantly greater than the void ratio of sample which was not under suction (saturated sample). It was also observed that at constant matric suction, the collapse potential of the soil increased initially to a maximum value with increasing net mean stress and then decreased at very high net mean stress. At any constant net normal stress, the soil collapsed upon wetting due to a reduction in matric suction. .