软土盾构近距离下穿地铁双圆隧道变形实测分析

为研究盾构下穿对地铁双圆隧道变形的影响，以上海地铁14号线盾构下穿地铁6号线双圆隧道为工程背景，对双圆隧道在前后2次盾构下穿过程中的变形进行实测分析。结果发现： 1）盾构穿越导致双圆隧道发生竖向隆起变形和双线差异变形产生的断面扭转变形，断面扭转变形引起的轨道变形难于控制； 2）双圆隧道竖向变形为隆起变形，其变形分布形态随切口位置变化而变化，穿越后交叉点附近呈现特有的“驼峰状”隆起分布； 3）2次穿越扰动与叠加效应显著，表现为隧道隆起变形时间延长，累计量增大，2次穿越引起的最大变形位置发生改变； 4）双圆隧道的扭转变形随切口位置呈波浪形动态变化，出现多个拐弯点，对其环缝受力与变形十分不利，第2次穿越时的扭转变形较第1次穿越有所减小； 5）双圆隧道断面最不利扭转出现时刻不同于隧道最大变形出现时刻，且扭转最不利位置与最大隆沉发生位置产生了错位； 6）盾尾注浆对双圆隧道变形的控制效果明显，但将导致双圆隧道的扭转变形增大。

Deformation Law of Shield Tunneling underneath an Adjacent DOT Metro Tunnel in Soft Ground

In order to study the influence of metro shield undercrossing tunneling on the deformation of double O tube （DOT） metro tunnel, the characteristics of the deformation of the DOT tunnel during Shanghai Metro Line No. 14 crossing underneath DOT tunnel on Line No. 6 twice are analyzed by in situ measurement. The results show that: (1) The shield undercrossing causes the vertical uplift deformation of the DOT tunnel and the torsional deformation of the cross section, and it is difficult to control the track deformation caused by the cross section torsion deformation. (2) The vertical deformation of the DOT tunnel is uplift deformation, the tunnel deformation is closely related to the incision position, and the curve near the intersection shows a hump shape after undercrossing. (3) The secondary crossing disturbance and superposition effect are significant, which are manifested as the extension of tunnel uplift deformation time, the increase of the accumulated deformation, and the change of the maximum deformation position during the two undercrossing processes. (4) The torsional deformation of DOT tunnel shows a wavy dynamic change distribution with the location of the shield tunnel incision, and there are multiple turning points, 〖JP2〗which is disadvantageous to the stress and deformation of the tunnel segment joint. Besides, the torsional deformation of the second undercrossing is smaller than that of the first undercrossing. (5) The time that the most unfavorable cross section torsion of the DOT tunnel appears is different from that of the maximum deformation of the tunnel, and the most disadvantageous torsional position and the position where the maximum tunnel uplift occurs locate in different areas. (6) The grouting at the shield tail is effective in controlling the deformation of the DOT tunnel, but it leads to the increase of the torsional deformation of the tunnel.