在兰渝铁路南坪隧道出口段施工中遇到浅埋偏压现象，围岩为软流塑状Ⅵ级围岩。采用地表管桩控制软流塑状围岩的溜塌；采用大拱脚及加强支护措施来控制变形坍塌；在暗挖施工中经过施工方案比选，采用三台阶预留核心土法；并在严密配套的洞内外监测技术的指导下，安全顺利的通过了浅埋偏压Ⅵ级围岩地段。

The exit portal section of Nanping tunnel on LanzhouChongqing railway is located in Grade VI plasticflow ground with unsymmetrical pressure. Pipe plies are installed from the ground surface to control the collapse of the plasticflow ground; enlarged arch feet and strengthened reinforcement are adopted to control deformation and collapse; 3bench excavation method with core soil is adopted on basis of construction scheme analysis and strict monitoring is performed inside and outside the tunnel. In the end, the tunnel driving successfully passes the shallowburied Grade VI ground with unsymmetrical pressure.