Dilatancy as a fundamental property of granular media
The term ‘dilatancy’ was introduced by O. Reynolds. He drew the attention of researchers to the property of granular media which is not possessed by known ‘fluids or solids’, namely, the property to change one’s volume in the process of change of shape or distortional strain. In 1886 Reynolds described experiments with water-saturated samples and proved that in cases where drainage is limited, dilatancy causes a steep drop of pressure in pores. Reynolds research led him to the conclusion that dilatancy is ‘a singular fundamental property of granular media’ which need a special consideration and description. Ideally, non-cohesive soils can be defined as soils, wherein the interior forces or intergranular connections influence the mechanical behaviour only insignificantly. The failure of non-cohesive soil always presupposes a change in the original grain packing, which takes place in the process of overcoming the forces of intergranular friction and gear, i.e. is expressed in shears.