长江漫滩区深大异形基坑施工对紧邻特大型桥梁影响及变形控制研究

随着地下空间资源的开发利用，越来越多深基坑呈现出开挖深、规模大、形状不规则等特点，其支护结构设计复杂，施工难度大，具有明显的空间效应。本文以南京地铁某基坑工程为例，分析基坑施工对邻近桥梁的影响。其场区位于长江下游漫滩相二元结构地层分布地段，上部软土层厚度大，下部承压含水层地下水位高、水量丰富，地质条件复杂，该基坑为典型的深大异形基坑，距离某大桥的双曲拱引桥仅为7. 2 m，由于之前桥梁已遭受其他地下工程施工产生的较大变形，所以后续工程对其影响变形控制要求极高。为此，该车站基坑支护结构设计基于地下空间实际功能采用设置分隔墙分区开挖及MJS超深工法墙综合变形控制方案。本文通过有限元数值模拟计算，开展复杂环境下基坑开挖引起的围护结构及桥梁桩基的变形预测分析，计算结果显示，该深大狭长异形基坑开挖对邻近桥梁沉降变形影响显著，通过设置分隔墙分区开挖及MJS工法墙进行变形控制，能够较好地控制基坑的空间效应，减少“长边效应”、“异形效应”等对桥梁沉降变形的影响。通过现场基坑开挖过程实际监测结果，验证这一综合变形控制方案的可行性。该研究成果对于类似复杂地质条件下深大狭长异形基坑的支护及施工设计具有很好的借鉴意义。

Study on the impact of deep and large shaped foundation pit construction on adjacent grand bridge and deformation control in diffuse beach area of Yangtze River

With the development and utilization of underground space resources, more and more deep foundation pits present the characteristics of deep excavation, large scale, irregular shape, etc., and their supporting structure design is complicated and construction is difficult, with obvious spatial effects. This paper takes a pit project of Nanjing subway as an example to analyze the impact of pit construction on neighboring bridges. The site is located in the lower reaches of the Yangtze River diffuse phase binary structure stratigraphy distribution section, the upper soft soil layer thickness is large, the lower pressurized aquifer water table is high, rich in water, geological conditions are very complex, the pit is a typical deep and large heterogeneous pit, away from the hyperbolic arch approach bridge is only 7.2 m, due to the bridge has been subjected to other underground engineering construction produced by a large deformation, the deformation that can be withstood is close to the critical value, so the subsequent project on the neighboring bridge. For this reason, the station pit support structure design based on the actual function of the underground space by setting partition wall partition excavation and MJS ultra- deep method wall comprehensive deformation control program. In this paper, by taking finite element numerical simulation to carry out the deformation prediction analysis of enclosure structure and bridge pile foundation caused by pit excavation in complex environment, the calculation results show that this deep, narrow and long shaped pit excavation has significant effect on settlement deformation of neighboring bridges, and the deformation control through the setup of partition wall subdividing excavation and MJS method wall can control the spatial effect of the pit and reduce the "long side effect", " heteromorphic effect" and other effects on the bridge settlement deformation. The feasibility of this comprehensive deformation control program is verified through the actual monitoring results of the on- site foundation pit excavation process. The research results are of good reference significance for the support and construction design of deep, narrow and long shaped foundation pits under similar complex geological conditions.