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北京地铁5号线崇文门站是在既有地铁隧道下方采用暗挖法施工的地铁车站,下穿段新建车站隧道断面宽24.2 m、高11.46 m,与既有地铁隧道结构间净距仅1.98 m。实测数据表明:施工引起的既有地铁隧道结构变形以沉降为主,沉降主要发生在导洞施工阶段;隧道结构呈刚体特征,沉降曲线近似线性,变形缝处隧道结构最大沉降31.26 mm,变形缝两侧最大差异沉降14.0 mm;道床则表现出一定的柔性特征,沉降曲线呈非线性;不协调沉降导致道床与隧道结构发生了脱开,最大脱开值12.7 mm,最大脱开范围7.0 m。采用灌浆加固对道床与隧道结构间的脱离区域进行了治理,并通过注浆对既有地铁隧道结构进行了抬升,最大提升值达16.0 mm,使既有地铁线路的高程损失得到了一定恢复,最终将既有地铁隧道结构沉降控制在16.75 mm内,确保了施工期间既有地铁线路的正常运营。
Beijing Subway Line 5 Chongwenmen Station is a metro station constructed under the existing subway tunnel by undercutting method. The cross section of the tunnel beneath the new section is 24.2 m wide and 11.46 m high, which is only 1.98 m above the existing metro tunnel structure m. The measured data show that the deformation of the existing subway tunnel caused by the construction is mainly subsidence, and the subsidence mainly occurs during the construction of the pilot tunnel. The structure of the tunnel is characterized by a rigid body and the settlement curve is approximately linear. The maximum settlement of the tunnel structure at the deformation joint is 31.26 mm, The maximum difference between the two sides is 14.0 mm. The ballast bed shows a certain flexibility. The settlement curve is nonlinear. The uncoordinated settlement leads to the disconnection between the ballast bed and the tunnel structure. The maximum disconnection value is 12.7 mm and the maximum detachment range is 7.0 m. Grouting reinforcement is used to control the detachment area between the ballast bed and the tunnel structure and the existing subway tunnel structure is lifted up by grouting to reach a maximum value of 16.0 mm so that the elevation loss of the existing subway lines is restored to some extent. Finally, the subsidence of existing subway tunnels will be controlled within 16.75 mm, ensuring the normal operation of existing subway lines during construction.