Optimization of the Construction Technology of Shallow-Buried Tunnel Entrance Constructed in Residual Slope Accumulation of Gravelly Soil

Abstract

The entrance of Tianshan tunnel was constructed in residual slope accumulation of gravelly soil while the massif at the entrance was considered as a potential landslide mass. In this context, landslide is very likely to occur to cause engineering accidents under the effects of tunneling construction disturbance and rainfall infiltration. By analyzing the engineering geological and hydrogeological conditions of the tunnel, the researchers discussed the original construction scheme of the tunnel entrance and decided to optimize the construction technology of the tunnel entrance. During the construction design, the stability of side and face-upward slope of the entrance was calculated first, which reaches a conclusion that the side and face-upward slope probably landslide towards the free face induced by rainstorms. Next, the potential landslide mass at side and face-upward slope of the tunnel entrance was optimized and governed by using the method of lengthening umbrella arches and increasing reverse pressure by filling soil. Finally, the “three-bench seven-step” method was utilized to replace the center diagram method and the reasonability of the excavation method was verified by comparison and analysis using three-dimensional numerical simulation. Thus, the construction efficiency can be improved on the precondition of guaranteeing the safety.