基于流固耦合的邻近高边坡深基坑变形性状分析

Deformation Character Analysis of Deep Foundation Pit Adjacent to High Slope Based on Fluid Solid Coupling

为研究软弱富水条件下邻近高边坡深基坑开挖对地层的影响,对邻近高边坡深基坑进行开挖、降水和支护过程进行耦合模拟与实测数据对比分析。以有效应力原理和比奥固结理论为基础,考虑地下水对基坑开挖的影响,建立流固耦合作用下三维数值模拟分析模型;依次分析降水和开挖对围护桩变形和临近高边坡位移的分布规律,结合现场实测数据对模型进行验证。研究结果表明:深基坑开挖和降水施工过程中,随着开挖深度的增加,围护桩水平位移也相应增加,最大水平位移发生在桩顶处;因围护桩有5 m的嵌固深度和与之配套的锚索支护结构,降水、开挖、支护三个施工依次进行,随着开挖深度与锚固深度的增加,锚固作用效果逐渐增强,导致降水施工时的围护桩水平位移随深度增加而减小,单次降水施工步引起的围护桩水平位移仅为邻近开挖施工步引起围护桩水平位移的50%;开挖和降水施工同样也对邻近高边坡竖向位移产生影响,邻近高边坡最大竖向位移点为第一监测点,即围护桩边界处,单次降水施工步引起的邻近高边坡竖向位移与邻近开挖施工步引起的邻近高边坡竖向位移相近,表明在开挖前对基坑进行降水可以提高邻近高边坡的稳定性。

In order to study the influence of adjacent high slope deep foundation pit excavation on strata under weak water-rich condition, coupling simulation and measured data were compared and analyzed for the process of excavation, dewatering and support of adjacent high slope deep foundation pit. Firstly, a three-dimensional numerical simulation model under fluid-structure interaction was established based on the principle of effective stress and Biot’s consolidation theory, considering the influence of groundwater on foundation pit excavation. Then, the distribution law of the deformation of retaining pile and the displacement of adjacent high slope caused by dewatering and excavation is analyzed successively, and the model is verified with the field measured data. The results show that in the process of deep foundation pit excavation and dewatering construction, the horizontal displacement of retaining pile is increased with the increase of excavation depth, and the maximum horizontal displacement occurs at the pile top. Due to the embedded depth of 5m and the supporting anchor cable support structure of the retaining pile, the horizontal displacement of the retaining pile is decreased with the increase of the depth during the precipitation construction. The horizontal displacement of the retaining pile caused by a single precipitation construction step is only 50% of that caused by the adjacent excavation construction step, and excavation and dewatering also affect the vertical displacement of the adjacent high slope. The maximum vertical displacement point of the adjacent high slope is the first monitoring point, that is, the boundary of the retaining pile. The vertical displacement of the adjacent high slope caused by a single dewatering construction step is similar to that caused by the adjacent excavation construction step. It shows that dewatering the foundation pit before excavation can improve the stability of the adjacent high slope.