高地应力作用下渭武高速木寨岭隧道围岩大变形灾变预测分析研究

Prediction and analysis on large deformation of surrounding rocks in the Muzhailing Tunnel of the Weiyuan–Wudu Expressway under high in-situ stress

为解决在建渭武高速木寨岭隧道施工过程中遇到的高地应力环境下软岩大变形问题,基于工程区已有地应力实测数据,利用ANSYS有限元软件建立三维地质模型,反演工程区地应力场,并结合Hoek围岩变形预测公式计算分析隧道围岩的变形量。结果表明:工程区的地应力场主要受断裂控制,其次还受到岩体强度和地形的双重影响,强构造变形区的水平主应力值普遍低于弱构造变形区,沿隧道轴线三向主应力大小关系为最大水平主应力(S_H)>最小水平主应力(S_h)>垂直应力(S_V),强构造变形区最大水平主应力值在G8区段最大,而在G6区段和G11区段最小;弱构造变形区的水平主应力值自G12区段开始逐渐增大,直至G14中段开始因埋深减小而逐渐降低。沿隧道轴线最大水平主应力方向总体为北东向,而在断裂间挤压构造带多偏转为北东东—近东西向。高速公路隧道围岩变形受岩体强度和地应力场的双重影响,其中,岩体强度占主导作用,围岩变形量主要集中在20~80 cm范围内,变形等级以中等和强烈为主。

This study aims to solve the significant deformation issue in the soft surrounding rocks under high in-situ stress encountered during the construction of the Muzhailing Tunnel on the Weiyuan–Wudu Expressway.We established a three-dimensional geological model to invert the in-situ stress field using ANSYS based on measured in-situ stress data in the engineering area.Then,we calculated and analyzed the deformation of the surrounding rocks by combining the inverted results with the Hoek deformation prediction formula.The result showed that the in-situ stress field in the engineering area was primarily controlled by faults,with secondary influences from rock strength and topography.In the intense tectonic deformation zone,horizontal principal stress values are generally lower than in the weak structural deformation zone.The relationship between the three principal stresses along the tunnel axis is SH>Sh>SV.The maximum horizontal principal stress in the intense tectonic deformation zone was the highest in the G8 section and the lowest in the G6 and G11 sections.In the weak structural deformation zone,horizontal principal stress gradually increases from the G12 section until it decreases due to reduced burial depth starting from the middle of the G14 section.The maximum horizontal principal stress orientation was generally in the NE direction,and the extruded structural belt between the faults was mostly deflected to the NEE–nearly EW direction.The deformation of the surrounding rocks was affected by rock mass strength and in-situ stress field,with rock mass strength playing a dominant role.The deformation of the surrounding rocks is mainly concentrated in the range of 20 to 80 cm,and the deformation levels are mainly moderate and intense.