双线盾构隧道下穿对既有暗挖大断面隧道影响的数值分析

Numerical Analysis of the Influence of Double Line Shield Tunneling on Existing Large Section Mined Tunnel

依托北京地铁19号线盾构区间近距离下穿既有地铁1号线暗挖大断面隧道工程,结合三维有限元数值模拟,分析新建盾构隧道自身变形和既有暗挖隧道的受力变形状态,并研究新隧道穿越工程中,注浆加固、管棚加固、综合加固3种加固措施对既有隧道的影响。结果表明:双线盾构下穿会造成既有隧道纵向沉降,且既有大断面隧道底部沉降曲线的波动幅值比小断面隧道的更大;盾构上方既有的隧道结构可以减小盾构穿越产生的地表沉降;综合加固措施对于减小盾构下穿时既有隧道底部产生的沉降和既有隧道上部地表沉降的改善效果最为明显;双线盾构下穿会使双线盾构之间的上方既有隧道拱顶结构内力增大,加固措施对既有隧道受力的改善效果并不明显。研究结果可为实际工程施工提供重要的理论指导,对于此类工程具有借鉴意义。

As a case of the shield tunnel of Beijing Subway Line 19 passing under the existing large-section mined tunnel of Beijing Subway Line 1,the deformation of the new shield tunnel,stress and deformation of the existing mined tunnel are analyzed based on three-dimensional finite element numerical simulation.On the basis,the effects of the three reinforcement measures of grouting reinforcement,pipe shed reinforcement comprehensive reinforcement on the existing tunnel during the crossing process of the new tunnel are studied,respectively.The results indicate that longitudinal settlement of existing tunnel is caused by the double track shield tunneling,and the fluctuation range of the settlement curve at the bottom of the existing large cross-section tunnel is larger than that of the existing small cross-section tunnel.The surface settlement caused by shield tunneling is decreased under the effect of the existing tunnel structure,and the bottom settlement of the existing tunnel and the surface settlement above shield tunnel during shield tunneling are also decreased by applying the comprehensive reinforcement measures.In addition,the vault stress of existing tunnel will increase due to passing-under the double line shield tunnel,and the effect of reinforcement measures on existing tunnel internal force is not obvious.The results provide important guidance and reference for practical engineering construction projects.