Crack development in a physical model of undisturbed expansive soil slope and core sample under wet-dry cycles

Cyclic wetting and drying in expansive soil slopes results in the formation of desiccation cracks and irreversible structural changes which can cause substantial reduction in overall soil strength leading to slope instability. This study investigates the structural and crack development in a physical model of undisturbed expansive clay slope and small core sample subjected to five wet-dry cycles. The surface distribution and vertical extent of cracks in the slope model was measured during the various drying and drying cycles. The crack intensity factor, which quantifies surface cracks increased with increasing wet-dry cycles and became constant in the third cycle. Vertical cracks whose bases are connected by near horizontal cracks or cracks parallel to the slope developed to a maximum depth of 28 cm in the physical model. The shallow depth and orientation of these cracks along the slope may be a contributing factor for the shallow infinite slope failure in expansive soils. In addition, suction and water content measurements were made during various cycles. Changes in suction occurred to a depth of 28 cm, and the maximum suction increased with increasing cycle number. The results also demonstrate boundary and size effects on crack formation.