深基坑开挖及降水引起的邻近浅基础沉降分析

在城市繁华地区进行基坑工程施工,需要重点考虑施工过程对周边环境的影响。论文以深圳某地铁基坑工程为例,模拟了深基坑内降水条件下的基坑开挖过程,分析了地铁车站深基坑开挖及降水引起的邻近浅基础建筑物沉降及支撑结构的变形。研究表明,基坑降水对周边建筑物的沉降有重要的影响,其影响在浅层土开挖时尤为显著,随着开挖深度的增加,降水产生的作用逐渐减弱。另外,降水的影响范围远大于土体开挖卸荷本身。连续墙嵌固在中风化岩中的方案与连续墙嵌固在微风化岩中的方案相比,邻近建筑物平均沉降有大幅增加,差异沉降也有小幅增加。同时,连续墙的底部侧向变形大幅增长。本研究对基坑开挖过程中邻近建筑物的保护有指导意义。

Settlement of Shallow Foundation Induced by Adjacent Deep Excavation and Dewatering

Deep excavation often causes displacement of adjacent structures.Hence,it is highly necessary for deep excavation in urban area to evaluate the effect of construction process on surrounding buildings.Based on a case of deep excavation of metro station in Shenzhen,the process of construction of the deep foundation pit(including alternating dewatering and excavation) was simulated by a finite element program in this study.Settlement of an adjacent shallow foundation and deformation of diaphragm wall were analyzed.It is found that dewatering has a significant effect on the settlement of shallow foundation.This effect is more significant during the excavation of shallow soil layers.With the increasing depth of excavation,the effect induced by dewatering is decreasing.Furthermore,the zone affected by dewatering is much larger than that by excavation.The analysis shows that as compared with the case where diaphragm wall is embedded in slightly weathered rock,average settlement of shallow foundation increases greatly,differential settlement increases only a little and the lateral deformation at the bottom of diaphragm increases greatly when the diaphragm is embedded in medium weathered rock.Recommendations are made for analytical modeling,design,and diaphragm wall construction and dewatering.This study is helpful in protecting adjacent buildings during a deep excavation.