软土地区基坑开挖对下卧隧道的影响分析

Influence of Excavation on the Underlying Tunnel in Soft Soil

隧道上方基坑开挖会引起下卧隧道的收敛变形,对某城市地下通道基坑开挖引起的下卧隧道收敛变形进行了系统的分析研究。结果表明,基坑开挖使下卧隧道产生横向压缩变形,隧道收敛变形的影响范围约为沿隧道轴线方向基坑长度的5倍。隧道收敛在基坑开挖区间较大并且向两侧减小。下卧隧道管片的横向压缩变形与管片的泊松比μ和土体的有效内摩擦角φ'有关。软土地区,隧道收敛变形的最大值一般出现在基坑边缘附近,基坑中心具有较小的收敛变形。基坑漏水使隧道上方土体产生附加应力,隧道发生横向拉伸变形。隧道收敛随基坑开挖时间的增加而增大,底板完成后隧道顶部由于上部竖向附加应力增加和底板的约束作用,隧道收敛变形具有一定的反弹。得到的结论可为相似工程提供参考和借鉴。

Excavation affected the convergence of underlying tunnel is analyzed. The horizontal compression deformation of tunnel caused by excavation and the influenced range of the tunnel is 5 times than the length of the foundation pit along the tunnel axis. The convergence of tunnel is big in the foundation pit area and decreases to both sides. Horizontal compression deformation of tunnels is related to μ and φ'. The maximum convergence of tunnel occurred at the edge of foundation pit. The convergence in center of foundation pit is smaller. The tunnel was subjected to additional force due to leakage and the horizontal stretching deformation of tunnel caused by force. The convergence of tunnel increase with excavation time and vertical additional force made the convergence of the tunnel to bounce back when the bottom plate finished. The results obtained in this paper can provide reference for similar engineering.