A review of mechanical over-closure and thermal over-closure of rock joints: Potential consequences for coupled modelling of nuclear waste disposal and geothermal energy development

摘要

Rough joints can over-close due to a prior higher stress, or due to temperature increase alone. There is better fit of their opposing walls causing increased friction and even tensile strength. Well-controlled laboratory HTM tests, in situ HTM block tests, and large-scale heated rock mass tests, lasting several years at Stripa, Climax and Yucca Mountain, have produced likely evidence for this coupled response, which is different from pressure solution. Rock mass deformation moduli, thermal expansion coefficients, hydraulic apertures, shear strength, and seismic velocities can each be affected. In the cooling phase of an HLW repository, and in a geothermal project, rougher joints may be thermally over-closed, and cooling causing contraction effects may be focused where joints are more planar, causing shear and fluid capture.