南京长江漫滩某深基坑换撑优化设计案例分析

A Case Study of an Optimization Design in Removal of Braces of an Excavation Foundation in Nanjing Yangtze River Floodplain

以南京长江漫滩软土地层下某明挖隧道基坑开挖施工为工程依托,针对该工程施工中遇到的拆撑、换撑问题,通过建立三维有限元模型和现场试验,分析拆撑对基坑稳定性的影响,提出采用坑底土体加固和增强围护结构两种措施来约束基坑变形、提高基坑的稳定性,从而避免了繁琐换撑,该优化方案经济快速.通过在现场试验段埋设力传感设备和位移监测点,观测拆撑后侧墙的受力变化特征,以及支护桩顶及周边地表的位移情况.试验段实测结果验证了换撑优化方案的可行性,利用该优化措施有效指导了全线基坑的拆撑施工.该成功经验可为类似工程设计和施工提供有益参考和指导.

Based on the excavation of an open-cut tunnel in Yangtze River Floodplain,Nanjing,a three-dimensional finite element model was established to study the problems encountered in the process of demolishing braces,and the stability of the pit during this process was investigated.The measures including reinforcement of pit bottom soils and reinforcement of retaining structure were both proposed to improve the stability of the pit to replace the complicated stage of removal of braces.The feasibility of this optimum design was analyzed preliminarily.Then,pressure transducers and displacement monitoring points were buried in the test section of this project.The internal force of the retaining walls,the displacement at the top of the walls,and the settlement of the ground surface were measured after the removal of braces.The results indicate that this optimum design is feasible,and can thus be extended to the whole project.The experience achieved has implications for design and construction of similar projects.