Abstract: The aim of this study is to probe into the reinforcement effect of splitting grouting on clay-rich tunnels from a mesoscopic viewpoint. The entrance segment of Wuzhuangcun tunnel of the Central Yunnan Water Diversion Project is taken as a research background. The PFC^2D model of splitting grouting is established by simulating the interaction between slurry and soil particles in the process of grouting based on the discrete element fluid-solid coupling theory, the plate narrow slit model and the secondary development of Fish language. The influences of grouting time step, grouting pressure, particle size ratio and cohesive strength on the slurry diffusion radius and soil porosity are studied. Results reveal that grouting pressure is the dominant control factor affecting the soil reinforcement effect. With the increase of grouting pressure, the slurry diffusion radius expands continuously and the porosity increases continuously. A smaller distance from the grouting hole results in a smaller influence on porosity. An optimal grouting pressure exists. Moreover, mesoscopic soil parameters have obvious influence on the macroscopic mechanical properties after grouting. With the increase of particle size ratio and cohesive strength, the slurry diffusion radius and porosity reduce significantly. The simulation results are in well agreement with indoor model test result, which verified the correctness of the simulated model.

Key words: clay, splitting grouting, discrete element simulation, fluid-soild coupling, model test, diffusion rule, Central Yunnan Water Diversion Project