Finite element analysis of influence of fracture stiffness changing with stress on thermo-hydro-mechanical coupling in dual-porosity medium

Introducing and modifying the continuously yielding joint model, and simultaneously considering the composite impact of mechanical dilation/compaction and pressure solution on fracture aperture, the FEM code for analysis of the thermo-hydro-mechanical coupling in dual-porosity medium established by the first author was improved. Through the numerical simulations in which there were two patterns of changing the fracture stiffness for a hypothetical nuclear waste repository, the variations and distributions of temperatures, fracture stiffnesses, normal stresses, pore (fracture) pressures, flow velocities of groundwater were investigated. The results show: compared with the case of unchangeable fracture stiffness, the temperatures in the computing domain are lower in the case whose fracture stiffness is an exponential function of normal stress; the magnitudes of stresses within the rock mass in two cases are also some different, but the characteristics of stress distribution are similar to those of fracture stiffnesses obviously; and the negative pore (fracture) pressures in the case with changeable fracture stiffness are smallish (about 98% of case of unchangeable fracture stiffness).