大断面隧道施工引起的上覆地铁隧道结构变形分析

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。

Structural deformation of overlying subway tunnels induced by tunnelling

The Chongwenmen subway station of Beijing Metro Line No.5 is the first one beneath the existing subway tunnel in China,which is constructed by use of the mining method.The newly-built subway station tunnel undercrossing the existing subway is 24.2 m in width and 11.46 m in height,and the distance between the newly-built tunnel and the existing subway structures is just 1.98 m.The monitoring data show that the structural settlement is the prominent response style of the existing subways,and the settlement mainly happens during the pilot-drift construction.The existing subway tunnel structures have obvious characteristics of rigid body,whose settlement curves are linear.The structural deformation slot of the existing subway tunnel has the largest settlement,31.26 mm;and the biggest difference settlement of the two sides of the structural deformation slot is 14.0 mm.The trackbed deformation curves are nonlinear,and the inconsistent settlement makes the trackbed disjoin the tunnel structure.The largest disjoining gap is 12.7 mm and the largest disjoining length is 7.0 m between the trackbed and tunnel structure.By filling grouting,the disjoining areas are filled.By uplit grouting,the existing subway tunnel structures are heaved up,and the largest upheaval reaches 16.0 mm.With the measures,the settlement of the existing subway structures is finally controlled to be less than 16.75 mm,and the existing subway line is normal during the construction.