Analysis of deformation of joint asperities and mechanical implications

The contact mode between interface asperities during direct shear testing and the shearing mechanism are analyzed. Two analytical methods are used to characterize the roughness profile of the joint interface: the variogram function and the gamma density distribution. After successive shearing at increasing normal loads, the joint interface smoothens. This trend is exemplified by the decrease in the sill of the variogram function, and by the simultaneousincrease of the shape parameter and the decrease of the scale factor of the gamma density distribution. The magnitude of the sills for various azimuths is used to construct the loop describing the directional behavior of the distribution of the asperities and the roughness variation after successive shearing cycles. The mean height reduction of the asperities after each consecutive shearing is used to determine the surface compliance of the joint interface. The procedures of the analysis are developed and illustrated with results obtained from direct shear tests on four rock types.