The importance of incorporating hysteresis effect in determining shear strength of unsaturated soil

Soil water characteristic curve (SWCC) can be defined as a graphical representation for the relationship of matric suction - water content of a soil. SWCC demonstrates soil's ability to retain water (capacity of the soil for water storage), thus, it shows the water content corresponding to each matric suction. SWCC can be measured either by drying or wetting the soil mass. The soil that has undergone drying and wetting exhibits two different curves, therefore there is no unique SWCC, the difference between these curves is referred to as hysteresis of soil. SWCC is used to identify several soil properties such as shear strength, the coefficient of permeability and grain size distribution. Most of the researchers consider only drying SWCC as it is easy to measure compared to wetting SWCC. This paper highlights the hysteresis effect and the significance of incorporating wetting SWCC in identifying soil properties such as shear strength and stress-strain response.