超深富水基坑开挖工程突涌以及变形分析

Analysis of surge and deformation of ultra-deep water-rich foundation pit excavation

以宁波轨道交通7号线明海大道站标准段超深基坑工程为例,通过模拟承压水作用条件下的基坑开挖模型,研究了基坑开挖对周围环境的影响。在数值模拟的结果基础上,结合基坑抗突涌验算,预测了地面沉降、地下连续墙的变形以及基坑内隆起变形,并进行了参数研究。结果表明:基于HSS本构模型模拟超深富水基坑开挖工程,地连墙水平变形值和坑底隆起变形均小于位移控制值,与现场实际和工程经验一致;经验算,基坑抗突涌与基坑底部稳定性均满足要求。因此无需进行降承压水处理以及坑底加固,现有施工方案已能满足工程的安全性考虑;参数研究表明,基坑变形对地下连续墙入土深度并不敏感。在宁波地区进行深基坑工程时,不建议采取增加地下连续墙深度的方式来控制变形。

This article presents a case study of the deep excavation project at Minghai Avenue Station on Line 7 of the Ningbo Rail Transit system in the field of civil engineering.By simulating the excavation model under pressurized water conditions,the study investigates the influence of excavation on the surrounding environment.Based on the numerical simulation results and combined with the surge-proof calculation of the excavation,predictions are made regarding ground settlement,deformation of the underground diaphragm walls,and uplift deformation within the excavation,while conducting parameter studies.The results indicate that using the HSS constitutive model to simulate the excavation of a deep and water-rich foundation pit,both the horizontal deformation of the diaphragm walls and the uplift deformation at the bottom of the pit are smaller than the displacement control value,consistent with on-site observations and engineering experience.According to empirical calculations,both the surge resistance of the excavation and the stability of the pit bottom meet the requirements.Therefore,there is no need for depressurization treatment or bottom reinforcement,as the existing construction plan already satisfies the safety considerations of the project.The parameter study shows that the deformation of the excavation is not sensitive to the depth at which the underground diaphragm walls are embedded.Hence,when carrying out deep excavation projects in the Ningbo area,it is not recommended to increase the depth of the underground diaphragm walls to control deformation.