管幕法下穿既有地铁隧道微变形控制技术

Study on Disturbance of Pipe Curtain Construction in Sandy Cobble Stratum

依托矿山法新建北京地铁8号线木—大区间正线下穿既有10号线盾构区间工程,采用FLAC3D建立空间三维数值模型对管幕施工及新建地铁隧道下穿既有地铁隧道施工过程进行了数值分析,研究在管幕预支护体系保护下新建地铁双线隧道近距离下穿既有地铁隧道施工对地层扰动变形的影响,并将数值模拟结果同现场监测结果进行了对比分析.结果表明:在管幕预支护体系作用下,新建隧道的施工对上部地层的扰动以沉降为主;新建地铁双线隧道施工中,左、右线隧道施工引起的土层沉降具有叠加效应;在管幕预支护体系作用下进行新建隧道近距离下穿既有隧道施工,能够将既有结构的沉降变形控制在允许范围内.

This research relies on shield interval engineering of the construction using the mining method of Beijing Metro Line 8 near the bottom of existing subway tunnel line 10.A three-dimensional numerical model is established by FLAC 3D to analyze the construction process of pipe curtain used in the construction engineering of new subway tunnel under the existing subway tunnel. Under the protection of the pipe curtain pre-support system in the engineering,the influence of the constructing process in new metro double line tunnel near the bottom of existing subway tunnel on the perturbation deformation of the stratum is analyzed,furthermore,the numerical solutions are compared with the field monitoring data. The conclusions can be drawn as following: under the action of the curtain support system, the construction perturbation of new subway tunnel to upper surrounding stratum is mainly stem from the settlement of the upper strata. During the construction of the metro double line tunnel, the subsidence caused by the construction of the left and right tunnels has the superposition effect. Under the action of the pre-support system, the existing structure settlement deformation derived from the constructing of new tunnels near the bottom of existing subway tunnel can be controlled within the allowable range.