Study On The Influence Zone Of Parallel Adjacent Construction Of The Shield Tunnel And The Mining Large Cross-section Tunnel

In recent years,China has continuously increased investment in the construction of urban underground rail transit.It not only provides comfortable,efficient,safe and efficient travel modes for urban residents,but also achieves the goal of alleviating urban traffic pressure.At the same time,it is also integrated with the nationwide railway network and is gradually being developed into an integrated transportation system with the "railroad + urban track" as the main body.The metro construction sites are mostly located in the central area of the city,surrounded by buildings and underground pipelines.Inevitably,during the construction process,the new tunnel maybe too close to the surrounding existing structures,or new tunnels are too close to each other.There is no research result to follow for the newly-acquired tunnel construction project with complex close-proximity.Therefore,further studies are needed to provide basis for the design and construction of similar projects.This article relies on the engineering,parallel adjacent construction of the shield tunnel and the mining large cross-section tunnel,between Houjiatang Station and Dongtang Station on the No.3 line of Changsha Metro.Based on the existing tunnel construction mechanical mechanisms and the results of the adjacent construction theoretical research,the mechanical mechanism during the construction process of the shield tunneling method and the mine method is analyzed using numerical simulation methods.The displacement was selected as the criteria for determining the proximity of the impact zone,and we can draw the influence zone pictures.Finally,a method for selecting the construction method which can ensure the safety of the tunnel construction process is proposed by combined with the results of model test.The main conclusions are drawn as follows:(1)The core problem that needs to be solved in the adjacent construction is the redistribution of stress in the surrounding rock.The redistribution of stress in surrounding rock is the area where tunnel construction will affect the surrounding environment and different construction methods also have different influence zone.(2)The effect of the tunnel construction sequence on the final ground surface settlement,the main reason for the ground surface settlement caused by the tunnel construction in the mine method.The effect of the new tunnel construction on the existing tunnel is achieved by changing the stress and displacement fields of the surrounding rock.The internal force of the existing tunnel structure will obviously increase near the new construction tunnel.The change of internal force is mainly reflected in the increase of axial force.(3)Considering the sequence of tunnel construction,we use the surface settlement decision criteria and structural deformation decision criteria to draw the impact zone for the shield tunnel and the mining tunnel.Under the same engineering background,the tunneling effect of the mining tunneling method is greater than that of the shield tunneling method.The scope of the strong influence zone when the shield tunnel is the second tunnel is smaller than the scope of the influence zone when the mining tunnel is the second tunnel.(4)Based on the design scheme adopted at the site construction,numerical simulations and model tests are conducted to verify the applicability of the influence zone of tunnel adjacent construction.In order to ensure the safety of close-to-connection construction,it is necessary to pay attention to monitoring and measurement.If necessary,the surrounding rock of the tunnel can be reinforced and the structural design strength can be increased.