断层带大纵坡隧道围岩变形控制及支护优化

Deformation Control and Support Optimization of Surrounding Rock in Large Longitudinal Slope Tunnel with Fault Zone

摘要:

为探究断层带大纵坡隧道围岩变形控制及支护优化方法,考虑泄洪排沙洞弧线段最大设计倾角、断层地质参数与锚杆、钢筋网等支护参数,并参考圣维南原理控制模型边界,采用有限元法,建立了断层带大纵坡隧道施工支护的分析计算模型,对围岩变形和支护结构受力进行计算与动态分析。结果表明:断层带大纵坡隧洞围岩稳定性较差,断层处围岩竖向位移相较于完整地层增大了0.8~1.5倍,水平位移增大了1.0~1.2倍,需结合工程实际加强大纵坡隧洞初期支护强度;竖直方向架立钢拱架围岩压力控制效果优于垂直于隧道轴线方向,增加钢拱架密度可有效降低钢拱架应力;最优钢拱架架立方式下拱顶、拱底、边墙的最大位移比数值模拟结果分别减小17.80%、36.31%、18.54%。现场监测结果表明,钢拱架支护效果显著。

Abstract:

To investigate the deformation control and support optimization methods of surrounding rock in a large longitudinal slope tunnel with a fault zone, by considering the maximum design inclination angle of the arc section of the flood spillway tunnel, geological parameters of the fault, and support parameters such as anchor rods and steel mesh, and with reference to the Saint-Venant’s principle to control the model boundary, the finite element method was used to establish an analysis and calculation model for the construction support of the tunnel. The deformation of the surrounding rock and the stress on the support structure were calculated and dynamically analyzed. The results show that the stability of the surrounding rock of the large longitudinal slope tunnel in the fault zone is poor. The vertical displacement of the surrounding rock at the fault increases by 0.8 to 1.5 times compared with the complete stratum, and the horizontal displacement increases by 1.0 to 1.2 times. It is necessary to strengthen the initial support strength of the large longitudinal slope tunnel in combination with the engineering practice. The control effect of surrounding rock pressure of steel arch erected in vertical direction is better than that in perpendicular direction. Increasing the density of steel arch can effectively reduce its stress. The maximum displacement values of the vault, arch bottom and side wall under the optimal steel arch erection method are reduced by 17.8%, 36.31% and 18.54% respectively compared with the results of numerical simulation. The on-site monitoring results show that the steel arch support has a significant effect.