HYDRO-MECHANICAL COUPLING TEST AND MESOSCOPIC NUMERICAL SIMULATION OF SANDSTONE WITH A SINGLE INFILLED JOINT

Abstract

Studies on the hydro-mechanical coupling of sandstone with a prefabricated joint should focus on variations in interior structures under the hydraulic coupling effect. However, existing experimental and numerical studies have emphasized the macroscopic mechanics of jointed sandstone, and only a few works have explained the permeability evolution of jointed rocks from the perspective of mesostructural changes. Here, a numerical model of the fluid–solid coupling discrete element was constructed at the mesoscale to study the triaxial compression mechanics and permeability evolution of jointed sandstone under osmotic pressure from the mesoscopic perspective. This model was based on a triaxial test performed on the mechanical properties and permeability of jointed sandstone at different prefabricated angles. The influencing laws of a prefabricated angle (a) under hydro-mechanical coupling conditions on the deviatoric stress–strain curves, failure mode, and permeability evolution of jointed sandstone were analyzed. Results show that a pressure circle with a large area existed in the prefabricated joint during the triaxial test, which indicate that the prefabricated joint is highly sensitive to hydraulic pressure. The anisotropy of soft bonding particles and different tensile crack/shear crack ratios under osmotic pressure leads to the varying peak strengths and failure modes of the samples. The microcracks formed by the bond failure of sandstone particles and the permeability of jointed sandstone at different prefabricated angles exhibit different variation laws with coordinated changes in mesostructure and microcrack. Research conclusions can provide theoretical references for studies on the mesomechanics of jointed sandstone under hydro-mechanical coupling behavior. Keywords: Hydro-mechanical coupling, Prefabricated joint, Fluid–solid coupling, Mesoscopic numerical simulation, Permeability