A Hydromechanical Model for a Single Rock Fracture Subjected to Shearing

Accurately predicting the hydromechanical behaviour of rock fractures is challenging due to the significant influence of shear-induced fracture geometries. This work proposes an improved shear-flow model that accurately estimates nonlinear fluid flow behaviour as well as shear mechanical behaviour. To predict shear mechanical behaviour, the model employs a modified multi-scale roughness shear constitutive model that accounts for water moisture effects. In addition, the evolution of the fracture void structure subjected to shearing is computed by a fracture void space model. A Forchheimer equation-based model incorporating fracture surface roughness and fluid flow tortuosity is introduced to model fluid flow nonlinearity. Laboratory shear-flow tests are conducted under constant normal stresses of 1, 1.5, and 2 MPa, utilising a newly developed shear-flow testing apparatus. The predicted shear mechanical and hydraulic behaviours of the fracture agree well with the experimental results, with \({\tilde{\sigma }}_{ave}\) ${\tilde{\sigma }}_{\mathit{ave}}$ of 11.6% for shear strength, NOF of 0.25 for shear dilation, and NOF of 0.14 for fluid flow rate. The proposed model improves the understanding and prediction accuracy of hydromechanical behaviours of fractures in engineering and geological applications.