基于强度折减法的软弱泥岩隧道围岩稳定性分析

Analysis on the tunnel surrounding rock stability of weak mudstone based on strength reduction method

由强度折减法确定的稳定性系数在差异较小时,难以确定最优开挖方法。为此,本文以蒙华铁路申家洼软弱泥岩隧道为例,借助FLAC3D软件,通过强度折减法确定三台阶七步法、三台阶临时仰拱法、中隔壁法、弧形导坑法等不同开挖方法的稳定性系数,对比不同方法开挖支护后不同部位塑性区面积比,确定最适宜的开挖方法。而后详细分析了最适宜开挖方法开挖支护后围岩的位移变化量、应力分布和塑性区变化特征。结果表明:三台阶临时仰拱法稳定性系数较大,塑性区面积比较小,为最适宜的开挖方法。采用该方法开挖后,隧道变形主要分布在拱顶、拱腰和仰拱部位。施加临时仰拱可有效抑制塑性区的发展,但拆除会造成应力的集中。

When the difference between the safety factors determined by the strength reduction method is small,it is difficult to determine the optimal excavation method.In order to solve this problem,this paper takes the Shenjiawa weak mudstone tunnel of the Menghua Railway as the research object,through the strength reduction method using FLAC 3D software,to determine the values of safety factor under different excavation methods.Comparing the plastic zone area ratios of different parts of the tunnel,the best excavation method is determined,and the displacement,stress distribution and plastic zone change characteristics of the surrounding rock after excavation and support are analyzed in detail.The results show that the safety factor of three-bench temporary lateral bracing method is larger and the area of plastic zone is smaller,which is the most suitable excavation method.After excavation using this method,the tunnel deformation is mainly distributed in the vault,arch waist and invert part.Applying a temporary inverted arch can effectively inhibit the development of plastic zone,while the disassembly will cause the concentration of stress.