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浙江大学学报(工学版)
浙江大学学报(工学版)  2021, Vol. 55 Issue (2): 338-347    DOI: 10.3785/j.issn.1008-973X.2021.02.014
土木工程、交通工程     
考虑邻近结构阻隔影响的基坑开挖前降水引发地层变形的特性
曾超峰(),王硕,袁志成,薛秀丽
湖南科技大学 岩土工程稳定控制与健康监测湖南省重点实验室，湖南 湘潭 411201
Characteristics of ground deformation induced by pre-excavation dewatering considering blocking effect of adjacent structure
Chao-feng ZENG(),Shuo WANG,Zhi-cheng YUAN,Xiu-li XUE
Hunan Provincial Key Laboratory of Geotechnical Engineering for Stability Control and Health Monitoring, Hunan University of Science and Technology, Xiangtan 411201, China
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摘要：

依托天津某地铁车站基坑实测资料开展一系列数值模拟研究，考虑邻近结构阻隔影响，探讨在坑外有/无地下结构及既有地下结构与基坑不同间距条件下开挖前降水引发的围护结构及坑外土体变形特性，通过对比各工况下基坑围挡与坑外土体变形模式、最大围挡侧移与最大地面沉降发展规律、墙后地表沉陷与基坑围挡侧移的面积关系等，揭示邻近结构对开挖前抽水引发基坑变形的影响机理. 研究表明，坑外地下结构的存在对地层运动发展有一定阻隔作用，且地下结构与基坑间间距越小，这种阻隔效应越明显；地下结构对其后方地层变形具有牵引效应，导致地下结构后方出现明显沉降槽，但随着地下结构与基坑间间距的增大，牵引效应不断减弱. 阻隔、牵引效应发挥的临界值分别为1倍、2倍的目标降水深度；当地下结构与基坑间间距处于相应临界值以内时，在基坑设计中应考虑阻隔与牵引效应的影响以得到更合理的支护与施工监测方案.
关键词： 基坑变形;  开挖前降水;  邻近结构;  阻隔效应;  牵引效应;  数值模拟    
Abstract:

A series of numerical simulations were carried out on the basis of a practical dewatering test in an excavation for metro station in Tianjin, to investigate the characteristics of wall and soil movement induced by pre-excavation dewatering considering the blocking effect of adjacent structure. The effect of the spacing between the existing structure and the excavation on the ground response was revealed. By comparing the deformation modes of retaining wall and soil, the development of the maximum wall and soil deformations and the relation between the soil loss areas induced by wall deflection and soil surface settlement, the influence mechanism of the adjacent structure on the dewatering-induced foundation pit deformation was revealed. Results show that the existence of surrounding underground structure limits the development of the ground movement, and a more apparent limiting effect would appear in the case with greater spacing between the underground structure and the excavation. In the meantime, the underground structure has a pulling effect on the ground behind it, leading to obvious surface subsidence behind the underground structure, but this pulling effect weakens continually with the increase of the distance between the underground structure and the excavation. In addition, the critical values of distance between the underground structure and the excavation were obtained to estimate the blocking effect and pulling effect, which were one and two times of the target dewatering depth. When distance between the underground structure and the excavation is within the corresponding critical values, the blocking effect and pulling effect should be considered during foundation pit design to yield more reasonable support scheme.
Key words: foundation pit deformation    pre-excavation dewatering    adjacent structure    blocking effect    pulling effect    numerical simulation
收稿日期: 2020-09-16 出版日期: 2021-03-09
CLC:  TU 46+3  
基金资助: 国家自然科学基金资助项目（51708206，51978261）；中国博士后科学基金资助项目（2019T120797）；湖南省自然科学基金资助项目（2020JJ5193，2020JJ4300）；湖南省教育厅资助项目（20A190，17B097）
作者简介: 曾超峰（1987—），男，副教授，博导，从事岩土工程科研与教学工作. orcid.org/0000-0002-0917-9815. E-mail： cfzeng@hnust.edu.cn
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引用本文:

曾超峰,王硕,袁志成,薛秀丽. 考虑邻近结构阻隔影响的基坑开挖前降水引发地层变形的特性[J]. 浙江大学学报(工学版), 2021, 55(2): 338-347.

Chao-feng ZENG,Shuo WANG,Zhi-cheng YUAN,Xiu-li XUE. Characteristics of ground deformation induced by pre-excavation dewatering considering blocking effect of adjacent structure. Journal of ZheJiang University (Engineering Science), 2021, 55(2): 338-347.

链接本文:

http://www.zjujournals.com/eng/CN/10.3785/j.issn.1008-973X.2021.02.014    或    http://www.zjujournals.com/eng/CN/Y2021/V55/I2/338

图 1  地铁车站基坑降水井及变形监测点平面布置
土层性质 H /m γ /（kN?m?3） K0 w /% e Es /MPa
粉质黏土 5.5 19.35 0.49 29.9 0.811 4.00
黏质粉土 11.0 19.30 0.43 26.5 0.792 8.26
粉质黏土 19.0 20.10 0.50 26.4 0.696 5.80
砂质粉土 24.0 20.15 0.42 21.9 0.640 8.71
黏土 27.0 19.75 0.55 30.4 0.764 5.98
砂质粉土 33.0 20.65 0.35 20.2 0.583 8.29
粉质黏土 37.0 20.50 0.39 22.4 0.611 7.26
粉砂 42.0 20.05 0.30 18.2 0.585 10.50
粉质黏土 50.0 19.30 0.39 23.8 0.676 6.20
表 1  土层分布及主要土性参数
图 2  围护结构侧移实测值
图 3  模拟实际基坑数值模型网格图
土性 H /m KH /（m?d?1） KV /（m?d?1） M κ λ
粉质黏土 5.5 0.1 0.1 0.979 0.0065 0.0553
黏质粉土 11.0 0.5 0.5 1.192 0.0036 0.0312
粉质黏土 19.0 5.0×10?4 1.0×10?4 0.979 0.0052 0.0445
砂质粉土 24.0 1.0 1.0 1.202 0.0034 0.0293
黏土 27.0 5.0×10?5 1.0×10?5 0.800 0.0046 0.0397
砂质粉土 33.0 1.0 0.7 1.202 0.0033 0.0283
粉质黏土 37.0 5.0×10?4 3.0×10?4 0.900 0.0037 0.0320
粉砂 42.0 2.5 1.5 1.382 0.0022 0.0191
粉质黏土 50.0 5.0×10?4 2.0×10?4 0.900 0.0035 0.0305
表 2  数值模型中土层分布及物理力学参数
图 4  坑外有/无地下结构时数值模型网格图
参数 取值/m
1）注：∞表示坑外无地下结构的工况
Hd 5.5、11.0、16.0、19.0、21.5
D 5、10、15、20、40、∞1）
表 3  模型计算工况与参数取值
图 5  C3测斜孔处侧移实测值与计算值对比
图 6  坑外有/无地下结构时开挖前降水引发基坑变形计算曲线
图 7  开挖前降水引发基坑变形时程曲线
图 8  最大基坑变形随地下结构与基坑间距变化
图 9  地下结构后方最大沉降随地下结构与基坑间距变化
图 10  最大围护结构侧移与最大地面沉降的关系
图 11  最大基坑变形增量随地下结构与基坑间距变化
图 12  围护结构侧移面积及地面沉陷面积随地下结构与基坑间距变化
图 13  土体损失面积求解示意图
图 14  坑外地面沉陷面积与围护结构侧移面积关系
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