基坑开挖前降水对围护变形影响分析

高水位地区基坑工程项目的预降水往往会引起基坑围护一定的初始变形，有时甚至超过开挖引起的变形量，而大多数基坑变形初值采集一般在预降水完成后，开挖前降水引起的围护初始变形问题较难引起重视，对相关案例分析研究就显得尤为重要。结合上海某基坑工程案例，通过该案例中开挖前降水监测数据分析，并进一步采用有限元模拟，得出基坑支护前降深过大将引起基坑较大水平变形，揭示了单独降水对围护变形的影响机理，为后续基坑工程评估预降水的变形影响提供借鉴。

Analysis of Dewatering Before Foundation Pit Excavation Influence on Enclosure Deformation

The pre-dewatering of foundation pit engineering project in high water level area often causes certain initial deformation of foundation pit support,sometimes even exceeds the deformation caused by excavation.However,most of the initial deformation values of foundation pit are collected after the completion of pre-dewatering,and it is difficult to pay attention to the initial deformation of retaining wall caused by dewatering before excavation,so it is particularly important to analyze relevant cases.Combined with a foundation pit engineering case in Shanghai,through the analysis of pre-excavation dewatering monitoring data,and finite element simulation was adopted to analyze the influence of dewatering before foundation pit excavation on enclosure deformation.The results show that excessive drawdown before foundation pit support will cause large horizontal deformation of foundation pit.The influence mechanism of separate precipitation on the deformation of retaining wall is also revealed,which can provide reference for the subsequent foundation pit engineering to evaluate the deformation impact of pre dewatering.