考虑基坑降水开挖影响的运营隧道变形分析

Deformation analysis of metro tunnels considering impacts of dewatering excavation in foundation pit engineering

以上海大型深基坑在建工程为依托,采用有限元数值模拟方法,研究了基坑降水及加固等施工措施对基坑开挖过程中地下连续墙水平侧移、坑外地层以及隧道变形的影响规律,计算结果与现场实测数据有较好的一致性.研究表明:地下连续墙两侧SMW工法加固以及坑内土体加固可有效控制周边地层以及临近隧道的扰动变形,在采取加固措施后上行线仰拱测点的沉降量降低43.2%;相对于跨层降水,采取逐层降水方案时,坑外地表沉降、地下墙水平侧移以及运营隧道水平和竖向变形的最大值分别减小4.8%,4.2%,12.3%和12.7%,通过优化降水方案控制临近隧道变形的效果较为明显.

Based on a Shanghai deep foundation pit projet, the excavation construction impacts of the dewatering and reinforcement measures on metro tunnels were investegated using the fi- nite element method. The rules for the horizontal displacements of diaphragm wall and sur- rounding soils, and the deformation of tunnels analyzed in the process of foundation pit excava- tion. The calculated results compared with measuring data and the good agreements observed. The results shows that the soil mixing wall （SMW） reinforcement for both-sides of diaphragm walls and the soil reinforcement inside the foundation pit have significant controlling effects on the disturbance deformation of the soils outside foundation pit and adjacent tunnels. The meas- uring point subsidence of up-line tunnel invert is reduced by 43. 2~ after construction rein-forcements. The maximum surface settlement outside the foundation pit, the maximum lateral displacement of diaphragm wall, and the maximum horizontal and vertical deformation of sub- way tunnels are reduced by 4.8%, 4.2%, 12.3%and 12.7% respectively in successive dewa- tering scheme, compared to cross-layer dewatering scheme. It is an effective way to control the tunnel deformation by optimizing the dewatering scheme.