Thermal Effects on Discontinuity Behavior: A Laboratory Scale Study

The growing global population is leading to reduced space and a need for more resources. This is causing engineered structures to be designed within rock masses at greater depths, and subjected to significant thermo-mechanical loading. Numerous hydro-thermo-mechanical in-situ experiments, including block tests and heated plate load tests have demonstrated the effects of temperature on discontinuity mechanics at a large scale. In this study we propose two methodologies for the multi-stage testing of discontinuity shear strength at incremental temperatures under triaxial conditions. The two methodologies result in different thermo-mechanical behavior of the specimens. If deformation of the specimen is constrained during heating, no change in residual shear strength of the discontinuity is seen, however, if the specimen is unloaded and free to deform under thermal loading, it displays reduced shear strength upon reloading. This preliminary data has potential implications for the design of engineered structures in these elevated thermo-mechanical environments.