复合地层双线盾构上跨既有地铁隧道施工诱发地表沉降分析

Study on Ground Surface Settlement Induced by Double Track Shield Tunnelling Upper-crossing Existing Metro Tunnel in Composite Ground

新建盾构隧道近距离上跨施工引起地表沉降受到多种因素的影响,导致工程实践中最常用的地表沉降估算方法 Peck公式具有一定局限性,与实测值相比存在较大误差。以佛莞城际线FGZH-1标段双线盾构上跨既有广州地铁7号线施工工程为背景,构建三维弹塑性有限元模型,分析复合地层双线盾构上跨既有隧道掘进诱发地表沉降规律,并结合现场施工数据监测,在传统Peck方程中引入修正系数(地层最大横向沉降值修正系数α1,地层横向沉降槽宽度修正系数α2),对经典Peck方程进行适用性修正。研究表明:当α1介于0~1.2、α2介于0.4~1.6之间可获得吻合较好的预测曲线。本研究可为复合地层双线盾构上跨既有隧道施工周围环境的保护提供理论依据。

The surface subsidence caused by the construction of the newly-buih shield tunnel is affected by many factors. The most commonly used method for estimating the surface settlement in engineering practice is that the Peck formula, which has some limitations. The section of FGZH-1 double line shield tunnelling over-crossing Guangzhou Metro Line 7 construction project is shown as the research background. 3D elastoplastic FEM is applied to analyze the ground surface settlement caused by construction of double line shield tunnel in complex stratum. On the basis of field monitoring data, two correction factors are introduced, namely, the maximum settlement correction factor at and the settlement trough width correction factor α2, which are used to modify the Peck formula under the specific conditions. The results show that when α1 is between 0 - 1.2, and α2 is between O. 4 - 1.6, the curves can give α good prediction. The research results could be helpful to the regional protection technology of multi-line overlapped shield tunnel construction and served as theoretical basis.