红层软岩作为一种特殊的地质结构具有变形量大及流变性的特点，在该地质条件下开挖隧洞可能会出现围岩大变形甚至发生失稳坍塌等安全事故。针对滇中引水工程的磨盘山隧洞部分洞段要穿过红层软岩地区并面临着围岩大变形的难题，采用有限元软件对隧洞围岩变形规律及支护措施进行数值分析。结果显示：隧洞开挖后洞周发生较大的应力集中，导致围岩变形量和塑性区范围较大，在软弱断层带部位变形量高达285．5 mm ，塑性区深度达10 m 左右，远远大于硬岩对应值。隧洞开挖后对围岩进行临时支护以及永久衬砌，两者对减小围岩变形量和塑性区范围均有较为明显的作用。%The red-bed soft rock is a special soft rock with the properties of large deformation and rheology ,therefore the tunnels excavated in this geological structure may be subjected to large wall-rock deformation even collapses and other safety incidents .Aiming at the great soft rock deformation problem during the excavation of the Mopanshan tunnel of the water diversion project in the middle of Yunnan province ,numerical analysis of the deformation of surrounding rock as well as the efffect of the supporting measures were conducted with a finite element software .According to the result ,the deformation of the surrounding rock and the range of plastic zone is very large due to the occurrence of stress concentration around the tunnel after the excavation ,with the largest deformation of 285 .5 mm ,and deepest plastic zone of 10m in the weak fault zone ,which is far greater than those of the hard rock .However ,the deformation and the range of plastic zone decreases obviously after the construction of temporary supporting and permanent lining measures after the excavation .
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