Discontinuities are prevalent in most rock masses and represent planes of preferential deformation and fluid flow. Shear displacements can significantly alter the hydro-mechanical properties of discontinuities and, thus, the hydro-mechanical properties of the entire rock mass. The importance of the network of discontinuities in controlling rock mass behavior has long been known and has led to an abundance of research on discontinuity shear strength and transmissivity. Although well-studied, key aspects of discontinuity behavior and characterization have received lesser focus, namely the evolution of asperity damage and discontinuity void space morphology as a result of shearing. In this paper, a methodology that combines the use of two recent technologies (micro-X-ray computed tomography and combined finite-discrete element modeling) is described to study these aspects of discontinuity behavior.


Rock mass discontinuities represent planes of relative weakness and enhanced hydraulic conductivity and, thus, have a significant influence on the hydromechanical behavior of the overall rock mass. While the shearing of rock mass discontinuities has been extensively studied in the past, there remains uncertainty surrounding the mechanisms by which surface asperities deform and degrade and how this degradation influences the aperture distribution.

Although many studies have attempted to investigate asperity failure mechanisms, they have been hampered by the lack of appropriate visualization and modeling tools. In particular, until recently it was not possible to observe asperity damage without physically separating the joint specimen or explicitly modeling the development of damage during a direct shear test.

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