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围岩变形机制及稳定性控制是隧道施工过程中关键技术之一。针对导洞超前开挖施工性态空间效应,采用有限差分软件FLAC3D模拟分析隧道施工过程中围岩变形规律,并与全断面法、上下台阶法作对比分析。研究表明:导洞超前开挖施工引起的水平收敛、拱顶沉降位移变化速率最小,开挖形成临空面之后产生的水平收敛和拱顶沉降值最小,有利于隧道围岩的稳定;水平收敛值随隧道埋深、侧压力系数的增大呈线性增大;拱顶沉降值随埋深的增大呈线性增大,随侧压力系数的增大呈非线性增大趋势;隧道埋深越大,水平收敛、拱顶沉降先行位移占总位移比例越大;侧压力系数越大,水平收敛先行位移所占比例越大,而拱顶沉降先行位移所占比例越小。结合宜巴(宜昌至巴东)高速公路石门垭隧道施工现场监测数据,验证所得结论的可靠性,可为同类工程借鉴,具有一定的科学意义和工程实用价值。
The deformation mechanism and stability control of surrounding rock are one of the key technologies in tunnel construction. In view of the spatial effect of pilot tunneling, the deformation of surrounding rock during tunneling is analyzed by finite difference software FLAC3D, and compared with the full-face method and the upper-lower step method. The research shows that the level induced by the advance excavation of the pilot tunnel converges and the displacement rate of the vault settlement is the minimum. The horizontal convergence and the settlement of the vault resulting from the excavation of the freeboard surface are minimum, which is in favor of the stability of the surrounding rock of the tunnel. The value of the vault increases linearly with the increase of the buried depth and the increase of the lateral pressure coefficient. The vault settlement value increases linearly with the increase of the buried depth and increases nonlinearly with the increase of the lateral pressure coefficient. Large and horizontal convergence, the greater the proportion of vault settlement ahead of total displacements; the greater the lateral pressure coefficient, the greater the proportion of horizontal convergence and the smaller the proportion of vault settlement. Combined with the monitoring data from the construction site of Shihmenya Tunnel on Yiba (Yichang-Badong) Expressway, the reliability of the conclusions obtained can be used as reference for similar projects, which has certain scientific significance and practical value.