Dilatancy of the interface between a structure and gravelly soil

Dilatancy is one of the key properties of the soil–structure interface. A number of monotonic and cyclic shear tests were analysed to derive the rules and the dilatancy mechanism of the interface between a structure and a gravelly soil; diverse influential factors were considered, such as soil type, roughness of the structure and normal stress. The volumetric change due to the dilatancy consists of a reversible and irreversible dilatancy component, each of which has different mechanisms, different rules and different control factors. The reversible dilatancy component is strongly dependent on the direction of the applied shear after an initial application of shear loading. The irreversible dilatancy component gradually increases owing to the continued application of shear and exhibits a close relationship with the evolution of the physical state. The volumetric change that is due to the dilatancy mainly depends on part of the tangential displacement which corresponds to the deformation of the soil that is constrained by the structure; such a part of the tangential displacement is significantly dependent on the state of the entire tangential displacement, on the normal stress and on the features of both the structure and the soil. The roughness of the structure, the behaviour of the soil and the normal stress have significant effects on the dilatancy behaviour of the interface.