Improvement of Laboratory Protocols for Discontinuity Geomechanical Characterization and Investigation of the Effect of Saturation on Granite Strength

Abstract

The Nuclear Waste Management Organization of Canada (NWMO) is currently in the process of site selection for the future development of a high-level nuclear waste Deep Geological Repository (DGR), and locations with crystalline bedrock are the top candidates (Hirschorn et al. 2017). In support of this process, a study on the effects of water-saturation on the geomechanical response of granitic rock is conducted. Rock-water interactions are investigated in both intact rock and discontinuities. This topic was investigated on two different granites: Lac du Bonnet and Pointe du Bois pink granites. The results of this study show no significant correlations between strength reduction and water content in granite in compression, tension, and confined shear. In addition to the investigation of rock-water interactions, this work also presents the development of a new direct shear sample preparation procedure as well as a technique for normal loading and direct shear test data processing and interpretation: joint deformation correction and analytical representation of joint pre-yield deformation. An exponential function is suggested to determine the instantaneous normal and shear stiffness values.