Research On Stability Of The High And Sleep Slop And Control Technique At The Double-arch Tunnel Entrance

Double-arch tunnel was convenient to link up the route and select the entrance position of tunnel,because of the particularity of the structure.So double-arch tunnel can be better suited for the complex terrain.In recent years,the double-arch was widely used when the tunnel was constructed in the mountains and hilly terrain,especially at the tunnel portals.However,the structure and construction process of the double-arch tunnel were more complicated and more likely to influence the stability of the tunnel.Because the wall rock of the tunnel hole was weathered seriously and accompanied by high slope,large bias,burial and other problems.The wall rock often ruptured and the slop became unstable in the tunnel construction process.Therefore,it was necessary to analyze the interaction between the stability of the slope and the wall rock.Based on the engineering practice,this paper analyzed the above problems through theoretical analysis and numerical simulation.The main research result of the paper were:(1)This paper summarized the current research on the slope stability at the tunnel entrance,analyzed the failure modes and mechanism of the slope of the tunnels,and summarized the relevant factors that affect the slope stability of the tunnel.This paper used the means of theoretical analysis to analysis the stability of slope in different stages of tunnel construction.According to the spatial position of the tunnel and the potential sliding direction of the slope,this paper studied the influence of the slope on the tunnel.Finally this paper determined the interaction mechanism between the deformation of the wall rock and the slope.(2)The paper established a three-dimensional numerical model about the slope of the double-arch tunnel in the specific condition and simulate the dynamic construction process about the central pilot method and the three-pilot method.Through comparing the evolution laws of the displacement field and stress field and evaluating the stability,this paper determined that the three-pilot method has a smaller effect on slope stability.(3)For the three-pilot method,this paper simulated different excavation sequence about the main hole and the guide hole and gets the variation of the displacement and stress of the slope,wall rock and partition wall.Analyzed and compared the change trend of the excavation of the displacement and stress of the selected point and obtained the influence degree of different excavation sequence on the stability of the slope of the tunnel.Comprehensive analysis showed that the reasonable excavation sequence was to excavate deep guide tunnel hole firstly,and reasonable excavation sequence of main tunnel hole was to excavate shallow main tunnel firstly.(4)This paper summarized the control technology,which was used to improve the stability of the slope at the tunnel entrance,and divided them into tunnel reinforcement measures and slope reinforcement measures.Simulated the construction process of three programs,which is no pre-support,slope anchor reinforcement and pipe roof support,and studied the effect of different support methods on the stability of high and steep slope of tunnel entrance.Comprehensive analysis showed that the pipe roof support can effectively reduce the deformation of slope,wall rock and partition wall,and when use the slope anchor reinforcement the deform of the slope can be better controlled.