Geomechanical Influences of Interface Dilatancy

This paper examines the influence of dilatant processes that can occur at a discontinuity of finite dimensions located at a compressed elastic geological interface, due to relative shear movement in the plane of the discontinuity. The dilatant phenomena will result in displacements in a direction normal to the shear movement and these displacements will be influenced by the elasticity of the geological materials and the compression at the interface. The dilatant displacements will also create a zone where there is loss of contact at the unilaterally constrained interface. The resulting problem is examined by appeal to results of the mathematical theory of elasticity. The influence of dilatant processes on the development of shear at the elastically constrained interface is examined by considering the procedures proposed by D.W. Taylor to analyze dilatant phenomena. The mathematical developments illustrate the combined influence of elastic constraints and interface compression on the amplification of the shear stress generated at the finite region. In the absence of dilatancy, the developments reduce to the classical result involving only Coulomb friction.