考虑空间效应的软土隧道上方卸荷变形分析

隧道上方基坑的空间效应对隧道变形存在较大影响，提出了一个新的可以考虑空间尺寸效应影响的卸荷比模型，该模型能综合考虑上方基坑深度、宽度和基坑沿隧道纵向长度的影响。通过三维有限元数值分析法和实测分析法，研究了上方基坑空间效应对隧道变形的影响。数值分析和监测数据表明，盾构隧道变形主要是由盾构隧道上方主要覆土区内的外部施工作业引起，主要覆土区之外基坑施工作业对隧道最大隆起量的影响较小，主要覆土区内隧道最大隆起量与提出的卸荷比近似呈线性关系。软土地区的隧道上方基坑工程可通过控制卸荷比来控制隧道的竖向变形。

Analysis of metro tunnel deformation by upper excavation unloading considering spatial effect in soft soil

The spatial effect of the foundation pit on the tunnel has a great influence on the tunnel deformation. In this paper, a new model of unloading ratio considering spatial effect is developed. It can comprehensively consider the influences of the depth，width and longitudinal length along the tunnel of the upper foundation pit. The three-dimensional finite element method and field measurement method are employed to determine the influence of spatial effect of the upper foundation pit on the tunnel deformation. Numerical result and field monitoring data show that the deformation of the shield tunnel is mainly caused by upper excavation unloading in the main overburden area over the shield tunnel, the construction of foundation pits outside the main overburden area has little effect on the maximum uplift deformation of tunnel, and in the main overburden area the maximum uplift deformation of tunnel is approximately linear with the unloading ratio proposed in this paper. In soft soil area the uplift deformation of the tunnel by upper excavation unloading can be controlled by controlling the unloading ratio.