深厚淤泥区基坑开挖作用下临近地铁基坑的力学响应

Mechanical Response of Foundation Pit Close to Metro under Excavation of Foundation Pit in Deep Silt Area

为确保处于深厚淤泥区的临近地铁基坑在新建基坑开挖支护过程中的安全性.通过有限元软件建立精细的三维计算模型,计算分析地铁基坑对新建基坑开挖、支护的力学响应特征。研究结果表明:开挖完成后,地铁车站基坑位移呈现岀“鼓肚型”,符合连续墙加内支撑基坑支护型式一般的变形规律;新建基坑围护桩最大侧移为24.5 mm,竖向位移为6.54 mm,均小于围护桩位移控制值,说明新建基坑支护体系设计具备合理性;地铁车站基坑围护结构最大位移为12.16 mm,远小于一级基坑位移限值。同时发现其地下连续墙两侧的位移增量不同,右侧(靠近新建基坑一侧)地下连续墙位移增量较小。其原因是新建基坑开挖淤泥区使右侧地下连续墙所受的主动土压力减少。

In order to ensure the safety of foundation pit close to metro in the deep silt area during the process of excavation and support of newly built foundation pit,a fine 3D calculation model is established through the finite element software to calculate and analyze the mechanical response feature of metro foundation pit to the excavation and support of the newly built foundation pit The study result shows that the displacement of foundation pit of metro station presents a"bulge shape"after the completion of excavation,which conforms to the general deformation law of diaphragm wall plus inner support foundation pit supporting type.The maximum sideway of the newly built foundation pit guard post is 24.5 mm and the vertical displacement is 6.54 mm,which are all less than the control value of guard post displacement,and shows that the design of newly built foundation pit support system is reasonable.The maximum displacement of the pit support structure of metro station is 12.16 mm,which is far less than the first displacement limit of foundation piL At the same time,it is found that the displacement increments at both sides of its underground diaphragm wall are different The displacement increment at the right side(close to one side of newly built foundation pit)is small.Its reason is that the excavation silt area of the newly built foundation pit makes the active earth pressure on the right underground diaphragm wall reduce.