非均质软弱围岩隧道注浆加固圈分布特性

基于随机分布理论和流-固耦合理论, 考虑注浆过程中围岩物性参数的动态变化和浆液黏度时变性, 推导了流-固耦合作用下非均质软弱围岩的浆液扩散方程, 并运用多场耦合软件COMSOL Multiphysics建立了小导管注浆浆液在非均质软弱围岩中的扩散模型, 系统研究了注浆参数与小导管布设等对浆液扩散与注浆加固圈形成的影响。研究结果表明: 浆液在非均质软弱围岩内以类椭圆形向四周扩散, 扩散形态随注浆压力、注浆时间与围岩参数等动态变化而不断变化, 最终趋于稳定; 在注浆过程中, 增大注浆压力和延长注浆时间在一定程度上可提高浆液的渗透能力并改善围岩的渗透性, 而适当的增大小导管布设长度或减小导管布设角度有利于注浆加固圈的形成; 为达到最优注浆效果, 洞头山隧道小导管预注浆加固压力宜设为1 MPa, 注浆时间宜控制在400 s, 小导管布设角度不宜小于30°, 布设长度应大于2.5 m; 经现场监测验证, 隧道围岩28 d抗压强度提高至2 MPa, 围岩渗透系数降至10-5 cm·s-1, 后续台阶法施工开挖拱顶沉降均小于3 cm, 围岩整体性和连续性得了显著提高。 

Distribution characteristics of grouting reinforcement ring for tunnel with heterogeneous weak surrounding rock

Based on the random distribution theory and fluid-solid coupling theory, the dynamic changes of physical parameters of surrounding rock and the time-varying viscosity of grouts in the grouting process were considered, a grout diffusion equation of a tunnel with heterogeneous weak surrounding rock under fluid-solid coupling was deduced. A grout diffusion model of small pipe grouting in heterogeneous weak surrounding rock was established by using the multi-field coupling software COMSOL Multiphysics, and the effects of grouting parameters and arrangement of small pipe on the grout diffusion and the formation of grouting reinforcement ring were systematically studied. Research result shows that the grout in heterogeneous weak surrounding rock disperses in a quasi-elliptical shape. The diffusion patterns change continuously with the dynamic changes of grouting pressure, grouting time and parameters of surrounding rock, and finally tend to be stable. In the grouting process, the permeability of surrounding rock and the penetration capacity of grout can be improved to a certain degree with the increases of grouting pressure and grouting time. While increasing the length of small pipe or reducing the angle of small pipe is beneficial to the formation of grouting reinforcement ring. To achieve the optimal grouting effect, the pre-grouting reinforcement pressure of small pipe in Dongtoushan Tunnel should be designed as 1 MPa, the grouting time should be controlled at 400 s, the angle of small pipe should not be less than 30°, and the length of small pipe should be more than 2.5 m. With the field monitoring and verification, the 28-day compressive strength of tunnel surrounding rock increases to 2 MPa, the permeability coefficient of surrounding rock reduces to 10-5 cm·s-1, the settlement value of vault roof excavated by subsequent step method is less than 3 cm, and the integrity and continuity of surrounding rock are improved significantly.