下穿运营高铁及地铁的交通枢纽深基坑数值分析

Numerical study on a deep excavation of transportation hub underlying operating railways and a metro station

某地下综合交通枢纽基坑下穿沪宁城际铁路和已建11号线地铁车站,周围环境复杂,铁路路基和地铁车站结构变形控制要求严格。采用有限差分软件FLAC3D对该深基坑施工过程进行三维数值分析,研究邻近铁路基坑、下穿铁路基坑以及已建地铁车站两侧共墙基坑开挖的引起的基坑围护结构和周围已有结构的变形特性,并采用现场实测数据对理论分析进行验证。通过对比分析计算结果和实测数据可知,铁路路基沉降和隧道隆起量均控制在允许范围内;采用坑内土体加固和加厚地连墙等措施可以有效地控制地连墙变形和邻近铁路路基沉降;已建地铁车站两侧共墙基坑开挖卸荷会导致地铁轨道的隆起,隆起量随共墙基坑卸荷量增加而增加;下穿基坑开挖和上部列车移动荷载共同作用下,铁路路基整体表现为上台。

The excavation of the transportation hub is located below Shanghai-Nanjing high-speed railways and metro station of Line 11. The surroundings are extremely complicated and the deformation controls of both the railway subgrade and the metro station are strict. 3D numerical simulation, using the FLAC3D, is carried out to model the construction process of the deep excavation. The deformation behaviors of the retaining structures and the surrounding existing structures are investigated during the construction of the adjacent pit, underlying pit and the pits sharing the same diaphragm walls with the existing structures. Numerical predictions are verified by the monitoring data. The results show that both the settlement of the railway subgrade and the rebound of the metro station are controlled within the allowable values, and the numerical predictions are reasonable and close to the monitoring data. Deformations of diaphragm wall and settlement of railway subgrade can be reduced by deepening and thickening the diaphragm wall and improving the soils. The soils excavated at both sides of the existing metro station will result in rebound of the structures, and the rebound depends on the unloaded volume. The overlying railway subgrade heaves as a result of the interaction of the underlying excavation and the train loads.