Permeability of Macro-Fractured Sandstone Samples under Cyclic Side-Confining Pressure

To better understand the relationship between permeability of fractured rocks and environmental confining pressure, we integrated results from experimental, analytical and numerical methods.In the experiments, we monitor the change in the permeability of fractured sandstone as confining pressure cyclically changes.The analytical models are the combination of hydro-mechanical coupling and fracture equivalence.Numerical simulation is based on the analytical models and used to further interpret the experimental measurements.We find that, 1) fracture permeability changes all by more than 50% for changes in confining pressure from 6MPa to 14MPa, 2) decreasing of fracture permeability with confining pressure has the feature of a negative exponential function, 3) pore pressure does not play an important role on seeping in fractures under high confining pressures, 4) the permeability is always lower in the second load cycle than in the first one for the same confining pressure.