Characterization of Mechanical Discontinuities Using Triaxial Shear Tests Under High Confining Pressure

Abstract

Mechanical discontinuities are defined as any surface through which some property of the rock mass is not continuous. Usually, the properties of the bulk rock separated by a discontinuity are used to predict the behavior of a formation. However, an analysis of the discontinuities as such is uncommon. The main property of a discontinuity is its shear strength. The shear strength has frictional parameters, such as basic friction angle and roughness, and may have a cohesion parameter. In this work, we evaluated the mechanical properties of artificial mechanical discontinuities. The artificial discontinuities were numerically designed. The mechanical performance of these discontinuities was initially assessed using published failure criteria that depend on the properties of the rock and the discontinuity morphology obtained by visual and 3D image analysis. Finally, triaxial direct shear tests under high confining pressure were performed to validate the criteria and assess their validity under different stress field conditions, properties of rock, and discontinuity morphology.