深基坑支护开挖对临近地铁隧道结构的影响分析研究

通过数值计算,采用考虑基坑开挖过程中土体剪切模量随应变增大而衰减特性的HSS模型,研究了基坑开挖卸荷作用下,邻近地铁隧道的埋深、隧道和基坑地连墙距离及刚度比等关键因素对地铁结构附加弯矩和附加位移的影响。结果表明:对于坑底隧道,在地下墙埋置深度范围内,与地连墙水平距离越大,隧道的侧移越小,在地下墙埋深以下,隧道侧移随与地连墙水平距离的增大而增大;通过比较坑侧与坑底隧道的附加弯矩与位移,得出地连墙底附近区域因基坑开挖卸荷引起的隧道附加弯矩较大,出现应力集中和明显的隧道-土-挡墙相互作用效应,坑侧隧道水平附加位移普遍大于竖向附加位移;此外,隧道与地连墙刚度比增大,对挡墙侧移和隧道附加位移都有明显的抑制作用。该研究揭示了基坑开挖作用下隧道-土-挡墙之间的相互作用规律,对深基坑开挖优化设计以及临近地铁结构的保护和安全运行具有一定的指导意义。

Numerical Investigation on Tunnel Responses Induced by Adjacent Deep Braced Pit Excavations

Extensive plane strain finite element analyses considering small strain effect were carried out to examine the tunnel responses induced by adjacent deep braced pit excavations in silty clay. The bending moments and displacements of the tunnel were studied by analyzing the influences of the key factors including the buried depth of the tunnel, the distance between the tunnel and the retaining wall and the tunnel stiffness ratio. The results indicate that, for tunnel beneath the pit, the lateral displacement of the tunnel decreases as the distance L-t increasing when it is above the wall toe. However, the lateral displacement of tunnel increases as L-t increasing when it is below the wall toe. It is obvious that the bending moments caused by excavation near the wall toe are significant, resulting in stress concentration and remarkable interaction effect between the tunnel, soil, and the retaining wall. Besides, the lateral displacement of the tunnel on the side of the pit is generally greater than the settlement. The lateral displacement of the retaining wall and the tunnel decreases as the tunnel stiffness ratio increasing. This study reveals the interaction of the tunnel-soil-retaining wall system subjected to braced pit excavation, providing guidance for the optimization design of the deep excavation and considering the safety of the adjacent tunnels.