The unified pipe-interface element method for simulating the coupled hydro-mechanical grouting process in fractured rock with fracture propagation

Abstract

Understanding the hydro-mechanical (HM) coupling grouting process in fractured rock masses is vital for improving grouting effects. In this paper, a hybrid formulation of the unified-pipe network method coupled with zero-thickness interface elements is developed for simulating fracture grouting, named the unified pipe-interface element method (UP-IEM). The UP-IEM can naturally capture both the initiations and propagations of cracks without enrichments or crack tracking algorithms. Additionally, the grout flow in both the porous medium and fractures is solved in one solution system. A semi-explicit frame is built for solving the hydro-mechanical coupling problems, avoiding the potential numerical instability of implicit solutions and long computation time of explicit solutions. The proposed UP-IEM for simulating curved fracture paths in the near-hole region is validated by several numerical tests. Then, a parametric study is carried out to investigate the parameter effects on grout-driven fracture tortuosity and injection pressure. Finally, a grouting model with multiple rows of grouting holes is established according to actual grouting engineering and the simultaneous fracture grouting and sequential fracture grouting processes are analysed. The results show that the UP-IEM is potentially useful for optimizing the fracture grouting process.