Modeling of Navier-Stokes flow through sheared rough-walled granite fractures split after thermal treatment

The Navier-Stokes flow through rough-walled granite fractures during shearing, where the fractures are prepared by splitting the granite blocks after heating and the onset of nonlinear fluid flow is closely related to the temperature and shear displacement, is modeled in this paper. The results show that as the temperature increases from 25 degrees C to 900 degrees C, the joint roughness coefficient of split granite surfaces increases from 16.07 to 21.62, following an exponential function.The predicted normal displacements during shearing under different initial normal stresses are consistent with the normal displacements in shearing reported in the literature, verifying the validity of the utilized expressions for calculating the shear-induced dilation. The rock strength weakens and the normal displacement decreases with the increment of surrounding temperature. As a result, the contact area increases, and the void spaces providing flow paths for fluids are decreased. The permeability holds constant at a small hydraulic gradient and then gradually decreases with increasing hydraulic gradient, indicating that the fluid flow transits from a linear regime to a nonlinear regime. The onset of nonlinear fluid flow can be quantify using the indicator of the critical hydraulic gradient which is positively proportional to the temperature and shear displacement and it ranges from 0.27 x 10(-3) to 6.71 x 10(-3).