软弱围岩隧道掌子面挤出变形特征分析

Characteristics Analysis of Tunnel Face Extrusion Deformation in Weak Surrounding Rock

软弱围岩在隧道工程中经常遇到,它的空间大变形特征受台阶长度、台阶高度、工法及地应力水平等条件的影响。结合兰渝铁路两水隧道现场监测和数值模拟相结合的方法对软弱围岩隧道的空间变形特征进行了详细分析。研究结果表明:围岩越弱掌子面纵向挤出变形大小及变形速率越大,掌子面挤出变形受上台阶断面开挖高度和围岩级别影响较受台阶长度影响显著;在洞周先行变形中,拱顶下沉较水平收敛更加明显;初始地应力场应力水平增高,隧道掌子面挤出变形会大幅增加。研究结果可为指导隧道的施工和设计提供有效依据。

Weak surrounding rock is often encountered in the construction of tunnel, whose space large deformation feature is affected by length, height, construction method and ground stress condition etc. Spatial deformation characteristics of weak surrounding rock tunnel were analyzed in detail based on field monitoring and numerical simulation of Lanzhou-Chongqing railway Liangshui tunnel. The results show that： the weaker the surrounding rock is, the larger tunnel face vertical extrusion deformation and deformation rate are, the tunnel face extrusion deformation is affected more by the upper step excavation height and surrounding rock level than step length; Among the pre-deformation of cave, the crown settlement is more obvious than the horizontal convergence; when initial ground stress level increases, the tunnel face extrusion deformation will increase sharply. The research results can provide effective basis for the design and construction of tunnel.