中文摘要：

为了减少和避免地铁盾构隧道发生运营中断事故,提升地铁盾构隧道的防灾减灾能力,应用数值模拟的方法,以上海某典型工程为例,研究了软土地层中,邻近基坑卸荷—加载作用下,盾构隧道位于基坑拐角特殊位置的变形机制,并对地下连续墙支护方案的隔离效果和盾构隧道与基坑边缘净距l的影响进行了分析。研究结果表明：1）当基坑位于盾构隧道侧方浅部时,基坑卸荷—加载诱发盾构隧道产生朝向基坑方向的位移,随着基坑加载的进行,竖向位移可得到适量恢复,水平位移恢复较少;2）当盾构隧道位于基坑拐角特殊位置时,受基坑临空面范围和卸荷—加载作用共同影响,最大竖向位移出现在基坑拐角位置附近,最大水平位移出现在隧道轴线距离基坑边缘约1.5h（h为基坑深度）位置;3）近地铁区域采用地下连续墙加固方案,可使盾构隧道水平位移减小50%,加固效果明显;4）当盾构隧道与基坑边缘净距l大于1.5h时,邻近基坑卸荷—加载对既有盾构隧道影响较小。

英文摘要：

The deformation mechanism of a soft soil shield tunnel in Shanghai adjacent to a foundation pit under the effect of unloading-loading of foundation pit is studied; the influences of the supporting scheme for underground diaphragm wall and the clear distance between shield tunnel and foundation pit on shield tunnel structure are analyzed.The study results show that： 1） The displacement of shield tunnel towards foundation pit would be induced by unloadingloading effect when the foundation pit is on the side of shield tunnel. The vertical displacement and horizontal displacement of shield tunnel would be recovered with the loading time increases. 2） The maximum vertical displacement of shield tunnel would occur nearby corner of the foundation pit and the maximum horizontal displacement of shield tunnel would occur at 1. 5h（ h is the height of foundation pit） point（ from tunnel axial line to foundation pit）under the effect of free surface scope of foundation pit and unloading-loading. 3） The horizontal displacement of shield tunnel would be reduced by 50% by setting underground diaphragm wall. 4） The unloading-loading effect of foundation pit can be ignored when the clear distance between shield tunnel and foundation pit is larger than 1. 5h.