基坑开挖及降水引起既有盾构隧道变形分析OA北大核心

Currently,foundation pit construction is trending towards"deep and large",involving extensive excavation areas often necessitating dewatering measures.To address the complexities of existing research,including intricate three-dimensional numerical analysis and modeling,and prolonged field measurement periods,a two-stage analysis method was proposed to calculate the mechanical deformation of existing shield tunnels under the combined influence of foundation pit excavation and dewatering.Initially,the additional stress exerted by the combined effects of pit bottom unloading,pit side unloading,and dewatering on the existing shield tunnel was computed.Subsequently,utilizing the Kerr foundation model and Timoshenko beam theory,the longitudinal deformation equilibrium differential equation of the existing shield tunnel was established,followed by solving the governing equation through the Galerkin method to analyze vertical deformation,joint openings,and joint dislocation.The effectiveness of the proposed method is validated through integration with an existing case.Furthermore,the impact of various factors on tunnel deformation under the combined action of foundation pit excavation and dewatering was examined.The findings are drawn as follows.(1)Dewatering significantly affects tunnel deformation,with the maximum uplift of the existing tunnel decreasing from 10.44 mm to 4.23 mm,a reduction of 59.5%,accompanied by slight decreases in joint openings and dislocation.(2)Certain characteristic points of tunnel deformation,such as 1 times the excavation width of the foundation pit and 1 times the equivalent radius of the dewatering well,exhibit susceptibility to sudden changes in joint openings and dislocation,necessitating special attention.(3)Alterations in pit excavation length or width induce notable changes and reversals in joint openings and dislocation,underscoring the significant influence of controlling the pit excavation dimensions on tunnel deformation.