盾构叠交穿越施工引起的既有隧道变形分析

针对上海新建11 号线盾构隧道夹穿地铁4 号线的工况, 采用数据监测的方法, 分析了先下后上穿越施工引起的既有隧道变形规律, 采用三次样条插值法对变形曲线进行了拟合, 并得出了穿越段全长纵向的变形曲率. 基于改进的隧道纵向等效化连续模型, 得出了隧道纵向变形曲率与环缝张开量的关系, 并结合行业规范, 对先下后上多层次穿越引起的既有隧道变形提出了建议控制指标. 研究结果表明: 新建隧道先下后上夹穿既有隧道时, 应控制开挖工程中的最大变形量; 内外圈的变形集中在上行线隧道中心线左右2.5 倍盾构外径范围内; 下穿施工时,外圈由于先期扰动, 沉降量较内圈更大, 先期扰动影响主要集中在外圈中心区域. 研究成果为地铁叠交穿越, 尤其是先下后上穿越既有隧道的保护提供了一定的理论基础.

Analysis of deformation of existing tunnel overlapped by new shield tunnel

As the newly-built Metro Line 11 in Shanghai went through Line 4, a method of data monitoring was used to analyze the deformation of the existing tunnel overlapped by Line 11 under construction with lower- and upper-shields. Cubic spline interpolation was used to simulate the deformation curve. A deformation curve of the full-length profile of the cross section was obtained. Based on an improved longitudinal equivalent continuous model of the tunnel, the relationship between the tunnel’s longitudinal deformation curve and the amount of stretching of the circular seam was calculated. Combined with the specifications, control indicators of deformation for the existing tunnel caused by Line 11 were proposed. The results showed that the maximum deformation in excavation engineering should be controlled first when the lower-shield was constructed, and then the upper-shield. At the same time, deformation of the inside and outside circle should be concentrated in its centerline around 2.5 times the outer diameter of the shield tunnel. In constructing the lower part, subsidence in the outer circle was larger because the outer circle was more influenced and the pre-disturbance was mainly concentrated in the outer center region. The results provided a theoretical basis for constructing overlapped metro lines, especially for protecting an existing tunnel when the lower-shield was constructed first.