极高地应力层状围岩隧道偏压演化规律及围岩控制

Unsymmetrical Loading Evolution Law and Surrounding Rock Control for Tunnels with Extremely High Geostress and Layered Surrounding Rock

以大峡谷隧道缓倾层状围岩为工程背景,采用3DEC离散元分析方法并结合现场监测的手段,深入研究高地应力不同岩层倾角下围岩偏压演化规律,揭示偏压与现场支护结构破坏关系,根据锚杆支护参数对偏压控制的影响,提出支护最优参数。研究表明,在高地应力缓倾岩层条件下支护结构的变形及破坏呈现明显的非对称性,随着岩层倾角的增大,初期支护最大主应力峰值位置由拱顶向右拱肩转移,反倾侧弯曲变形大于顺倾侧滑动变形;随着锚杆长度的增加,围岩剪切滑移区、初期支护位移、初期支护最大主应力均逐渐减小,锚杆最优长度约为3.5~4.5 m,锚杆沿层理面垂直方向打设,初期支护结构的偏压现象得到明显改善;现场优化支护后,左右拱肩呈对称变形,位移量基本相同,偏压得到明显改善。

Taking the gently inclined layered surrounding rock of the Grand Canyon Tunnel as the case, and adopting the 3DEC discrete element analysis method and combining with the means of field monitoring, the evolution law of the surrounding rock unsymmetrical loading under the high geostress and different dip angles of rock stratum is deeply studied, the relationship between the unsymmetrical loading and the field support structure damage is revealed, and the optimal support parameters are proposed according to the influence of the bolt support parameters on the unsymmetrical loading control. The research shows that the deformation and failure of the support structure under the condition of high geostress and gently inclined rock stratum show obvious asymmetry. With the increase of the dip angle of rock stratum, the peak position of the maximum principal stress of the initial support shifts from the crown to the right shoulder, and the bending deformation of the anti-dip side is greater than the sliding deformation of the down dip side. With the increase of bolt length, the shear slip zone of surrounding rock, the initial support displacement and the maximum principal stress of the initial support gradually decrease. The optimal length of the bolt is about 3.5~4.5 m, the bolt is set along the vertical direction of bedding plane, and the unsymmetrical loading of the initial support structure is significantly improved. After the field optimization of support, the left and right shoulders are symmetrically deformed, the displacement is basically identical, and the unsymmetrical loading is significantly improved.