深厚富水砂性地层深基坑开挖降水变形特性研究  

Deformation Characteristics of Deep Foundation Pit in Thick Water-Rich Sandy Strata Caused by Dewatering

作　　者：张誉津 刘俊城 谭勇 ZHANG Yujin;LIU Juncheng;TAN Yong(Department of Geotechnical Engineering,Tongji University,Shanghai 200092,China)

机构地区：[1]同济大学土木工程学院,上海200092

出　　处：《隧道建设（中英文）》2023年第9期1511-1522,共12页Tunnel Construction

基　　金：国家自然科学基金(42177179)。

摘　　要：为深入探究富水砂性特殊地层(地下水位高、砂层厚度大、渗透性强,止水帷幕通常无法完全隔断坑内外水力联系)深基坑开挖降水变形规律,基于南通某地铁车站实例,建立三维流固耦合有限元数值模型,对地下连续墙侧向位移、坑外地表沉降及坑底隆起等变形指标展开系统分析,并总结富水砂性地层深基坑变形特性。研究表明:1)深基坑土方开挖与坑内降水均会导致显著的墙体侧移和坑外地表沉降,其中,各施工阶段仅由降水引起的墙体最大侧移增量和坑外地表最大沉降增量分别占其对应阶段总增量的20%~40%和20%~60%;2)深部第Ⅰ承压含水层降水影响范围为0~90 m,第Ⅱ承压含水层降水影响范围可达180 m以上;3)随着开挖深度的增大,抗拔桩对基坑坑底隆起变形的约束效果会更加明显。Deep foundation pits in thick water-rich sandy strata are characterized by a high groundwater table,thick sandy layer,and high permeability;hence,water connections between the interior and exterior of the foundation pits cannot be cutoff completely.Therefore,a case study is conducted on a metro station in Nantong,China,to investigate the deformation patterns induced by dewatering in deep foundation pits within such strata.A three-dimensional fluid-solid coupling finite-element numerical model is constructed to systematically analyze the deformation indices such as lateral deflections of the diaphragm wall,ground settlements outside the foundation pits,and uplift of the foundation pit floor.The results reveal the following key findings:(1)The excavation of the foundation pits and subsequent dewatering activities result in severe lateral deflections of the diaphragm wall and surface settlements outside the foundation pits.The maximum increments in the lateral deflections of the diaphragm wall and surface settlements outside the foundation pit,caused by dewatering during the excavation,account for 20%~40%and 20%~60%in total,respectively.(2)The influence zone of dewatering in the first confined aquifer ranges from 0 to 90 m,whereas in the second confined aquifer,it extends beyond 180 m.(3)With increasing excavation depth,the antiuplift piles demonstrates an enhanced restraining effect on the heaving of the foundation pit floor.

关 键 词：富水砂性地层 深基坑 降水 数值模拟 变形特征 

分 类 号：U45[建筑科学—桥梁与隧道工程]