An Improved Model for Evaluating the Hydraulic Behaviour of a Single Rock Joint Considering Contact Area Evolution During Shearing

The contact of rock joints during shearing induced by underground excavation significantly impacts the hydro-mechanical behaviour of fractured rock mass, since fluid tends to flow through a rough-walled fracture along connected channels while bypassing the contact areas with tortuosity. However, previous research mostly considered joint roughness or aperture changes based on 2D joint profiles, while the contact and tortuosity using 3D surfaces were often overlooked. This paper considers the evolution of contact area and aperture distribution during shearing. The concept of the critical inclination angle is introduced and correlated with the contact area during shearing based on Grasselli’s criterion. The standard deviation of the mean mechanical aperture is calculated using the modified algorithm. An improved model for estimating the hydraulic aperture with the mechanical aperture is then developed, applying an aperture correction term and a contact correction term. A number of shear-flow tests on artificial joint samples under constant normal loads are conducted. The accuracy and reliability of the proposed model are verified by comparing it against the experimental results and by comparing the prediction performance with other published models. Results show that the proposed model can improve the prediction of the hydraulic aperture and hydraulic conductivity of a single rock joint during shearing.