Nonlinear seepage mechanical model and bifurcation analysis for fluid-solid coupling in fractured rock mass

With the development of underground engineering and oil and gas exploitation, the problem of fluid-solid interaction in fractured rock mass has become increasingly prominent, and its complex coupling mechanism has a profound impact on the stability and safety of engineering. The coupling effect between fluid and solid skeleton in fractured rock mass under the interaction of stress field and seepage field is discussed in this study. Based on the effective stress principle, the effective stress formula including porosity is constructed, and the governing formula of elastic fluid-solid coupling stress field considering the deformation of solid skeleton is developed. By introducing non-Darcy seepage formula and continuity formula, the control formula of seepage field is derived. The results show that the saddle-junction bifurcation occurs when the boundary stress does not change with time. When the boundary stress changes with time, it has a significant effect on the coupled seepage system. In the long time scale, the system reaches the stable state slowly, the volume strain changes slowly, and the boundary stress is obviously affected. This study provides a theoretical basis for understanding the interaction between fluid flow and solid deformation in fractured rock mass.