竖井工法开挖深基坑对下卧既有隧道上浮的控制

基坑开挖会导致下卧隧道产生明显上浮,采用竖井工法开挖基坑可有效的控制下卧隧道的上浮。以深圳地铁11号线区间某深基坑为例,采用考虑小应变刚度特性的硬化土模型,建立隧道与基坑共同作用的三维有限元模型,对比不同控制措施对隧道的保护效果,并研究竖井开挖基坑过程中下卧隧道的上浮规律。结果表明:竖井工法开挖基坑可以较好的控制隧道上浮,开挖过程中隧道的上浮值与卸载率呈现线性关系;坑底加固对抑制基坑底部土体上浮有较明显的效果;在开挖深度较低情况下,隧道上浮与开挖深度呈线性关系,随着开挖深度增加开始向非线性关系转化;若竖井工法开挖不能满足控制要求,可考虑增加坑底加固方式控制下卧隧道上浮。

Study on the Control of Floating of the Existing Tunnel Under the Deep Foundation Pit Excavation by Shaft Construction

The excavation of the foundation pit will cause obvious floating of the underground tunnel.This paper takes a deep foundation pit in the section of line 11 of shenzhen metro as an example, adopts the hardened soil model considering the small strain stiffness characteristics, establishes the three-dimensional finite element model of the interaction between tunnel and foundation pit, compares the protection effect of different control measures on the tunnel, and studies the floating law of the underground tunnel in the excavation process of shaft excavation.The results show that the floating of the tunnel can be controlled well by the shaft excavation, and the floating value of the tunnel has a linear relationship with the unloading rate.The reinforcement of pit bottom has obvious effect on preventing the soil from floating on the foundation pit bottom.When the excavation depth is low, there is a linear relation between the tunnel floating and the excavation depth.If the shaft excavation method cannot meet the control requirements, the bottom reinforcement method can be added to control the floating of the underground tunnel.