基坑开挖对邻近既有下卧隧道的影响分析

运用ABAQUS有限元软件，对下卧地铁上、下行线隧道顶、侧、底面的水平和竖向位移进行了三维数值模拟计算和对比分析，结果表明：基坑开挖对邻近既有下卧隧道的变形影响明显，位于基坑中部位置以下的隧道竖向位移相对较大，靠近基坑边缘位置的隧道水平位移相对较大；同一隧道顶部位置的竖向位移大于侧面和底部的位移，隧道侧面的水平位移大于顶、底部的位移；受基坑开挖卸荷的影响，隧道的自身变形表现为竖向直径增大，水平向直径减小。对位于既有隧道上方的基坑开挖要引起关注。

Influence analysis of foundation pit excavation on nearby underground existing tunnels

The three - dimensional finiie element simulating and its results of the horizontal and verti- cal displacement of the top, the side, the underside of metro and downlink tunnels were carried out by the ABAQUS finite element simulation analysis software . The results show that there are obvious effects of foundation pit excavation on underground existing tunnels and the vertical displacement of the tunnel locating in the central position of the foundation pit and the horizontal displacement of the tunnel locating in the edge position of the foundation pit are relatively large. What~ more, the vertical displacement of the top is larger than the side and the underside of the same tunnel and the horizontal displacement of the side are larger than the top and the underside of the same tunnel. In the effect of excavation unloading, the deformation of tunnel performance that the vertical diameter increases and the horizontal diameter decreases. We should pay more attention to the foundation pit excavation loca- ting above the existing tunnel.