Investigating the thermo-hydro-mechanical evolution of a UK geological disposal facility due to disposal of high-heat-generating wastes

The heat released from the disposal of High-Heat-Generating Waste (HHGW) in a Geological Disposal Facility (GDF) will result in an increase in temperature, and therefore thermal expansion of both the engineering materials and surrounding rocks. The changes to the stress state arising from the thermal expansion of these materials, restrained by the surrounding rock mass, could affect several of the Thermal, Hydraulic, and Mechanical (THM) processes that operate after closure of a GDF. In this paper a methodology is described which suggests how the influence of thermal stress on fracture aperture around a GDF can be evaluated. A set of calculations on an illustrative Discrete Fracture Network (DFN) are reported. These calculations estimate the responses of the fractures to changes in rock stress, considering changes in fracture aperture and the resultant changes to effective intrinsic permeability.