Experimental and theoretical study on the seepage mechanism characteristics coupling with confining pressure

To investigate the effect of confining pressure Pc on the seepage mechanism characteristics, a new model of seepage mechanism characteristics coupling with confining pressure has been proposed and analyzed. In this model, fracture closure deformation based on the hydraulic aperture is used to combine with Goodman hyperbolic model of fracture. In theory, the physical relationship among confining pressure, seepage pressure and flow rate has been established. For further validating the model, hydro-mechanical tests through single cutting shale fracture sample were conducted in the core holder at different constant seepage pressures (600, 1000, 1400 and 1800 kPa) or different constant flow rates (3, 7, 11 and 15 mL/min) under different confining pressures. The theoretical relationship was used to fit the hydro-mechanical test data, and the result showed that the suggested model could effectively predict the seepage mechanism characteristics. Based on the data of seepage tests under normal stress for shear fracture on diabase rock samples, the regression results shown that the model of seepage mechanism characteristics coupling with confining pressure can be applied well. This research result will contribute to the fracture seepage problem caused by change of in-situ stress in engineering projects. •A new model of seepage mechanism characteristics coupling with confining pressure has been proposed and analyzed.•Seepage tests were performed on fractured shale sample under confining pressure to prove theoretical model rationality.•The model was verified by other literature and could be applied to other experiments and projects.