Study On Excavation Interval Of Small Clear Distance Parallel Tunnel

With the development of society,people are becoming more and more strict with traffic,including single line tunnel,horizontal double line tunnel,upper and lower parallel tunnel,three line parallel tunnel and so on.The tunnel can be designed as a parallel double line tunnel to meet the specifications allowed by the terrain and geological conditions.In order to further reduce the area and reduce the cost of the tunnel,the small distance tunnel enters our life.The difference between the small distance tunnel and the ordinary tunnel is that the net distance is less than the minimum net distance stipulated in the standard.In addition,the advantages of the small distance tunnel are more than the general form of the tunnel,and the environment protection,the conservation of the land resources,the optimization of the route of the project.The construction of small distance tunnel should take full account of the influence between the two tunnels,so it is necessary to design the supporting measures which correspond to the small distance tunnel.Other factors include: net size,distance of the tunnel buried depth,geological conditions,tunnel face about line spacing,construction method and construction steps.This paper is mainly based on the parallel small distance tunnel project of Guangzhou metro line 21.Changping Station of Guangzhou metro line 21 interval has small spacing parallel tunnel construction,tunnel left line caused by multiple disturbance of surrounding rock.In order to avoid the stress superposition of the surrounding rock,determine the reasonable supporting time and minimize the deformation of surrounding rock,the appropriate excavation method and the appropriate excavation spacing are the key to the success or failure of the project.In order to ensure the safety and duration of the tunnel project,through the establishment of a finite element analysis model,different excavation methods and different excavation spacing are numerically simulated.Through the analysis of different excavation methods and different excavation spacing,the vault subsidence and the horizontal clearance value are compared with the actual engineering data.(1)under the condition of the V type surrounding rock,the tunnel is combined.The suitable excavation method is the single sidewall heading method.(2)under the condition of V surrounding rock,the most reasonable excavation interval between the two tunnels is 40 m.The research results provide feedback for actual tunnel construction.