The Influence of Asperities, Joint Topology and Stress on Fracture Geomechanical Properties

ABSTRACT: Joint roughness directly affects the behaviour of discontinuities at the laboratory scale and the rockmass at the excavation scale. For the design of large underground infrastructure projects (e.g. deep base tunnels for transportation and deep geological repositories for the storage of nuclear waste), laboratory testing is required to measure geomechanical properties (e.g. strength and stiffness) for input to numerical models. This paper presents an analysis of the influence of joint surface topology and confining stress on joint strength and joint stiffness from direct shear testing. Joint topology is analyzed using Structure-from-Motion photogrammetry models of drill core specimens and used to discuss the influence on joint strength and stiffness. Joint topology was found to influence joint stiffness at lower confining stress conditions with decreasing influence as the confining stress increases. Finally, the effect of applied stress is discussed with implications for joint stiffness and joint strength.