Calculating the Permanent Displacement of a Rock Slope Based on the Shear Characteristics of a Structural Plane Under Cyclic Loading

When a rock mass shears along a structural plane, the shear resistance of the structural plane is affected by the structural plane undulations and by the friction between the contact regions. During an earthquake, the seismic load (composed of the cyclic and dynamic loads) produces a dynamic deterioration of the mechanical properties of the structural plane, which is mainly reflected as follows: (1) under cyclic shear of the seismic load, the undulant angle alpha(k)decreases. (2) Under the dynamic load, the frictional coefficient of the structural surface is reduced. The dilatancy angle is generally used instead of the undulant angle. When calculating rock slope stability, the frictional angle is equivalent to the sum of the basic frictional angle and the undulant angle. In this study, the equations for calculating the dilatancy angle of a structural plane under cyclic shear loading are determined based on cyclic shear tests of a split structural plane. The basic frictional angle for calculating the cyclic shear is also determined, based on previous research. Furthermore, according to the dynamic model of a rock slope, a method to calculate the permanent displacement of the rock slope is proposed, considering the effect of structural plane deterioration. We found that the effect of structural plane deterioration under a seismic load directly affects the stability and permanent displacement of the rock slope. The feasibility and engineering practicalities of this method are also verified by comparing the proposed method with previously developed methods.