近距离下穿盾构隧道对上覆运营地铁隧道的影响研究

Influence of the Approaching Construction of Underlying Shield Tunnels on Overlying Metro Tunnels

盾构隧道掘进对邻近建筑物影响问题一直是个工程难题。文章采用有限元法对近距离下穿盾构隧道施工进行模拟,分析了新建隧道动态掘进时既有隧道的位移变化规律。基于双面弹性地基梁理论与盾构隧道纵向等效连续化模型,推导了既有地铁隧道受新建盾构隧道开挖影响管片张开量的计算公式,计算分析了管片张开量分布规律。分析结果表明:盾构掘进时对上覆斜交隧道影响区域主要在新建隧道轴线两侧2D(盾构直径)范围内;既有地铁的竖向位移主要分布在盾构掘进面前方2D和盾尾后1.5D范围内产生;既有地铁盾构隧道管片在新建隧道轴线正上方左右两个接头处张开显著,出现塑性变形。工程中需以既有地铁与下穿隧道相交处为轴,对既有地铁隧道侧向2D范围及两隧道间土层进行局部加固,以防新建隧道掘进引起既有地铁隧道纵向变形与张开过大。

The effects of shield tunnelling on adjacent buildings have long been a serious problem. In this paper, the approaching construction of an underlying shield tunnel was simulated by the finite element method and the displacement variation law of the existing metro tunnel during construction of the underlying shield tunnel was analyzed. Based on the double-sided elastic foundation beam theory and the shield tunnel longitudinal equivalent continuous model, a calculation equation for the segment openings of the existing metro tunnel affected by con- struction of the new shield tunnel was deduced and the distribution law for the segment openings was analyzed. The analysis results show that： 1） the area of the overlying, obliquely crossing metro tunnel affected by shield tunnel construction is mainly located in the range of 2D （D=tunnel diameter） on both sides of the new shield tun- nel axis; 2）the vertical displacement distribution of the existing metro tunnel is mainly within the range of 2D a- head of the working face and 1.5D behind the shield tail; 3） the segment opening of the existing metro tunnel ap- pears obviously at the two joints （left and right） directly above new the shield tunnel axis and is accompanied by plastic deformation; and 4） the area within 2D of the sides of the existing metro tunnel and the soil layer between the two tunnels should be locally reinforced to prevent longitudinal deformation and excessive segment opening of the existing metro tunnel associated with the new shield tunnelling.