Stability study of fluid-solid coupled dynamic system of seepage in accumulative broken rock

According to the non-Darcy Forchheimer phenomenon of water seepage in broken rock and fluid-solid interaction between the stress in surrounding rock and pore pressure in fluid of accumulative broken rock in goaf, the dynamic system stability of fluid-solid coupled seepage in broken rock is studied by nonlinear dynamic theory. According to the effective stress theory, the control equations containing the seepage variables were developed for the stress field, and the kinematic equations containing the volumetric strain were established for the seepage field by the motion equations of water seepage, the continuity equation of the broken, and the fluid. Correspondingly, the nonlinear dynamic equations of fluid-solid coupled seepage in accumulative broken rock were constructed, and then based on differential dynamic theory, the equilibrium state of the seepage system in broken rock tending to compaction state is solved and the stability of the equilibrium state is analyzed; at last, the dynamic responses of pore pressure, seepage velocity, and volume strain under different seepage parameters are obtained. The research indicates that there are hysteretic bifurcations and folding mutation in the fluid-solid coupled seepage dynamic system of broken rock, which is prone to sudden changes at bifurcation points, leading to water inrush and other dynamic disasters. This study can provide theoretical reference for the prediction of instability of the seepage system in broken rock.