大断面软岩隧道开挖空间效应影响分析

以长城岭软岩隧道为背景,通过现场监测和数值模拟,分析了隧道施工过程中围岩变形的三维空间演化规律,得出不同施工工法、断面尺寸和围岩等级对隧道开挖面空间效应的影响;结合正交实验和极差分析得到三类因素对开挖面空间效应影响的优先次序。结果表明:开挖面从逼近监测断面到通过监测断面再到远离,围岩主要经历了预变形、急剧变形和变形稳定3个阶段;软弱围岩的三维扰动深度沿开挖、竖直和水平方向分别在1.5、3和1倍洞径内;开挖工法对围岩变形的影响程度大小关系为全断面开挖法>台阶法>CD法;围岩等级越低,隧道断面尺寸越大,围岩变形量和范围越大;通过正交实验结合极差分析的方法得出对围岩变形的影响优先次序中围岩等级＞断面尺寸＞施工方法。

Analysis on Influence of Spacial Effect on Excavation of Soft Rock Tunnel with Large Cross Section

Taking Changchengling tunnel as background, the three-dimensional evolution law of surrounding rock deformation during tunnel construction was analyzed by the method of field monitoring and numerical simulation, which led to impacts that different construction method, section size and surrounding rock grade had on the spacial effect of tunnel excavation face. The priority of the influence of these three factors on the spatial effect of excavation face was obtained through combining orthogonal experiment and range analysis. The result shows that the surrounding rock mainly experienced three stages (pre-deformation, sharp deformation and stable deformation), when excavation face approached, passed and leaving the monitoring section; three-dimensional disturbance depth of deformation of surrounding rock was within 1.5, 3 and 1 times tunnel diameter in the direction of excavation, vertical and horizon; the influence degree of excavation method on surrounding rock was that step-method is greater than CD-method but less than full-face excavation; the worse the rock is and the larger the section is, the larger the rock deformation and its range are; the priority of the influence was that section size is greater than excavation method but less than grade of the rock, which was obtained by the method combining orthogonal experiment and range analysis.