Research On Comprehensive Construction Technology Of Bias Metro Stations With Combination Of Normal Construction Method And Top-down Method

Based on the construction of Shenzhen urban rail transit metro station,this paper research the design and construction of the metro station by means of theoretical analysis,numerical calculation and engineering practice.The main research results are as follows:The main technical problems of the enclosure structure and process comparison.Aiming at the spatio-temporal evolution of deformation and failure of surrounding rock and retaining structure during excavation of ultra-deep foundation pit,the displacement value of the stratum increases with the increase of excavation depth of different foundation pits.The standard "arch deformation" of the left side pile,the upper side pile and the lower side pile of the foundation pit in the early stage of excavation: the maximum horizontal displacement value appears in the middle position of the pile,and the displacement of the pile top and the pile bottom is relatively small,and the base The deformation of the right pile of the pit is a "forwardly inclined" deformation.The deformation modes of the retaining piles at various positions in the middle and late excavation are similar,showing a kind of "bow deformation" : the maximum displacement value appears in the middle of the pile(15m from the surface),and a certain displacement is also generated at the top of the pile.During the construction process,the construction technology of the middle partition wall was adopted in the deep foundation pit,which improved the construction speed of the project.The numerical study on the space-time evolution of the stability of the partition wall in the excavation process is carried out,and the distribution law of stress and deformation inside the wall is revealed.The middle to the bottom of the middle partition wall is mainly pressed,and the range of the pressure receiving area is gradually reduced as the depth of the excavation is deepened.In addition,there are obvious stress relaxation zones and stress concentration zones in the middle partition wall.From the analysis results of the maximum principal stress and the minimum principal stress,the top of the wall is the tensile stress relaxation zone,and the central zone of the wall has the compressive stress concentration zone.At the same time,an optimized construction method for integrated excavation of the station entrance and exit and the foundation pit main engineering is adopted.The analysis shows that the integrated construction method of the foundation pit and the auxiliary structure can ensure the stability of the stratum and the retaining structure and greatly accelerate the construction progress of the project.Significantly improve the economic benefits of engineering technology.In the case of the intersection of the subway station and the planned municipal tunnel,an integrated method for the construction of the reserved tunnels for the excavation of the municipal tunnel is used.The temporary support system is used to solve the problem of excessive vertical span of tunnel nodes.The T-beam is used to satisfy the problem of insufficient negative bending moment of the node support.The entire reserved node stress system relies on the station beam and frame structure.The complex transformation of the metro station and the municipal tunnel is complicated.The comprehensive construction technology of the ultra-deep metro station with biased reverse construction method is studied.Based on the actual working conditions,the key parameters of the construction were compared and selected,and the comprehensive construction technology of the metro station with the combination of the ultra-deep and reverse-biased construction was formed.