To accurately evaluate the disturbance effect of foundation pit excavation on the subway tunnel structure directly underneath,a 3D refined finite element model was established to analyze the disturbance characteristics of deformation and stress on subway tunnel structures at different stages of excavation,based on the intersection project of highway open excavation foundation pit project and a subway shield tunnel.Combined with on-site monitoring results,the deformation control effect of combined reinforcement measures such as MJS method+triaxial cement mixing pile foundation reinforcement,bored piles com-bined with cement retaining wall,portal reinforcement+anti-floating plate+counter-pressure box and basin excavation was verified.The results show that(1)The middle part of the pit bottom has the most significant unloading effect,which is the key part of pit excavation deformation control.The uplift deforma-tion of the longitudinal center section of the subway tunnel can be up to 4.55 mm,the uplift deformation of the tunnel structure near the edge of the pit excavation is generally 1～2 mm,and the uplift deformation of the subway tunnel outside the boundary of the pit excavation is less than 1mm.(2)Disturbed by the MJS method,enclosure piles,column piles,etc.,the subway tunnel structure produces a small bulging deforma-tion during the pit reinforcement stage,and the bulging deformation of the subway tunnel structure increa-ses with the continuous unloading of the subsequent pit excavation.Tunnel longitudinal section bulge de-formation is symmetrical distribution,the tunnel cross-section uplift deformation shows M-type distribu-tion,the deformation of different lines of the deformation curve shape varies,which has relation with the tunnel axis and the pit excavation boundaries diagonal angel.(3)The maximum values of field-measured rumble deformation of the left and right line shield tunnels are 5.35 mm and 5.16 mm respectively,and the horizontal convergence of the tunnels in the core zone of influence manifests itself as an inward contrac-tion,while the horizontal convergence of the tunnels in the non-core zone of influence manifests itself in the form of an outward expansion.At the same time,no structural damage was found in the subway tunnel dur-ing the on-site inspection,indicating that the pit deformation control and reinforcement measures taken were reasonable and feasible.The results of the study have important reference value for the deformation control and selection of reinforcement measures for the existing tunnel structure near the pit excavation.
关键词
基坑开挖/地铁隧道/隆起变形/数值模拟/结构内力
Key words
Pit excavation/Subway tunnel/Uplift deformation/Numerical simulation/Structural force
维普
万方数据