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北京地铁4号线宣武门站分离式双洞隧道近距离垂直下穿既有2号线地铁车站。从整体变形和单个块体位移2个角度对既有车站实测位移进行分析,得出浅埋暗挖隧道近接施工分步开挖过程中上覆地铁结构的变形规律:(1)既有地下结构整体沉降符合Peck曲线变形规律,而2个变形缝之间的块体结构位移则以转动为主,呈现刚体运动特征;(2)Peck公式拟合得到的地层损失率为0.118%~0.187%,其大小与既有地下结构是否存在、开挖断面大小无明显联系,而与新建隧道支护体系架设时机及刚度密切相关;(3)拟合得到沉降槽宽度系数为2.44~3.87,为相同埋深天然地层的1.05~1.62倍,沉降槽宽度系数与支护体系刚度无关,而与工前地层加固、既有地下结构的存在有关,且其大小与开挖面积基本呈线性关系。研究结果可为类似工程提供借鉴及参考。
Beijing Subway Line 4 Xuanwumen Station split double-hole tunnel vertically under the existing Metro Line 2 subway station. From the perspective of overall deformation and displacement of a single block, the measured displacement of an existing station is analyzed, and the deformation of the overlying metro structure during the step-by-step excavation of shallow-buried tunnel is obtained. (1) The existing underground structure The overall settlement is in accordance with the Peck curve deformation law, while the displacement of the block structure between the two deformation joints is dominated by rotation, showing the characteristics of rigid body motion. (2) The formation loss rate obtained by the Peck formula fitting is 0.118% -0.187% Its size is not related to existing subsurface structure and excavation section size, but closely related to the timing and stiffness of the new tunnel support system. (3) The width coefficient of settlement channel is 2.44-3.87 1.05 ~ 1.62 times higher than that of deep natural strata, and the width coefficient of settlement trough has nothing to do with the stiffness of supporting system, but is related to the reinforcement of pre-construction strata and the existing subsurface structure, and its size is basically linear with the excavation area. The research results can provide reference and reference for similar projects.