Study On Construction Technology Of Subway Underground Tunnel Adjacent To Deep Foundation Pit

In recent years,as the main mode of transportation,subway has been developed rapidly in major cities.However,due to the restriction of urban space,it is inevitable to meet the phenomenon of subway construction adjacent to deep foundation pit in the construction process of urban subway.The paper regards the interzone tunnel between ZhongShan square and DongLi Station as the research object.Based on the problems during the process of construction,a numerical simulation model is established to study the stress and deformation law caused by the truncation of the anchor cable and the appropriate excavation method of tunnel with different spans in adjacent deep foundation pit.The main findings are as follows:(1)When the prestressed anchor cable is not truncated,the excavation of the foundation pit is simulated by the way of finite difference software FLAC3 D.Then,on this basis,the anchorage section of prestressed anchor cable is truncated in different lengths.With the analysis of the change regulation to the axial force of prestressed anchor cable,the horizontal displacement of pile and the surface subsidence,it can obtain the influence of anchor cable partition to the stability of foundation pile,which can solve the problem that the prestressed anchor cable invades the tunnel in the process of actual construction.(2)In order to select appropriate excavation method of tunnel with different spans in the near deep foundation pit,the numerical model of tunnel with different spans is established according to the construction design drawing.The tunnel is excavated with double side drift method,CRD method and step method.Besides,we can receive the safe and economical excavation method by analyzing the stress and displacement of the initial support and the foundation pit.(3)By collecting and analyzing the monitoring and measuring data obtained in the actual project,the deformation of the tunnel can be effectively predicted during the construction,so we can adjust the construction technique and support parameters in time,which can ensure the safety of the construction effectively.