基于HSS模型的上海地铁深基坑开挖变形分析

为研究上海软土地区地铁深基坑开挖的变形性状,选取上海地区一典型软土地铁深基坑,基于土体小应变硬化模型(HSS模型)和相应的模型参数,采用PLAXIS 3D软件对该基坑的开挖过程进行了三维有限元数值模拟,并结合现场监测的数据对基坑围护结构的侧移和坑外地表沉降进行了对比。结果表明:使用HSS模型和合适的模型参数可以有效地模拟基坑开挖过程中的变形性状,实测结果与有限元分析结果相吻合,具有很好的工程实用价值; 该上海地铁深基坑的最大地表沉降与围护结构最大侧移间的关系符合上海地区最大地表沉降与围护结构最大侧移间的统计关系; 围护结构的最大侧移深度发生在基坑的开挖面处; 长窄型地铁深基坑仍存在较明显的空间效应,基坑长边中部的变形大于基坑角部,在长窄型基坑的设计和施工中应采取针对性措施。

Analysis of Deep Excavation Deformation of Shanghai Metro Station Using HSS Model

To analyze the deformation of the metro station deep excavation in Shanghai, the excavation process of a typical metro station in soft soil area was numerically simulated by using PLAXIS 3D with the small strain hardening model(HSS model)of soil and appropriated model parameters. The horizontal displacements of retaining structure and the settlements of ground surface behind walls were compared through the field monitoring data. The results show that the deformation in the excavation can be effectively simulated by the HSS model with appropriate model parameters. The simulated results are consistent with the measured results, which has a good engineering practical value. The relationship between the maximum ground settlement and maximum horizontal displacement of the retaining structure agrees well with the measurement statistics in Shanghai. The maximum horizontal displacement of the retaining structure usually occurs near the excavation surface. The long and narrow shape of the metro station deep excavation has an obvious space effect that the deformation near the middle span of pit is larger than that near the corner, which should be carefully considered in the design and construction of long and narrow metro station excavation.