基于离散元模拟的黏土劈裂注浆扩散特性

Diffusion Characteristics of Clay Splitting Grouting Based on Discrete Element Simulation

为从细观角度研究劈裂注浆对富含黏土隧洞的加固效果,依托滇中引水工程伍庄村隧洞进口段,采用离散元软件PFC 2D,基于离散元流固耦合理论、平板窄缝流动模型与Fish语言的二次开发,实现了注浆过程中浆液和土体颗粒的相互作用,建立了颗粒流劈裂注浆数值模型。研究了注浆时步、注浆压力、颗粒粒径比及黏结强度对浆液扩散半径及土体孔隙率的影响。结果表明:注浆压力是影响土体加固效果的主控因素,随着注浆压力的增大,浆液扩散半径不断扩大,孔隙率持续增加,与注浆孔距离越远,对孔隙率影响越小,存在最优注浆压力。土体细观参数对注浆后宏观力学特性有较为明显的影响,随颗粒粒径比和黏结强度的增大,浆液扩散半径及孔隙率明显减小。将数值模拟结果与室内模型试验结果对比,发现二者趋势吻合较好,与实际相符,验证了所建立的注浆数值模型的正确性。

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.