悬挂式止水帷幕条件下深基坑开挖变形特性研究

向朱锋; 徐金明

doi:10.16030/j.cnki.issn.1000-3665.202208019

悬挂式止水帷幕条件下深基坑开挖变形特性研究

doi: 10.16030/j.cnki.issn.1000-3665.202208019

向朱锋,
徐金明^,

上海大学土木工程系，上海　200444

详细信息

作者简介:
向朱锋（1997-），男，硕士研究生，主要从事岩土工程的研究工作。E-mail：xiangzhufeng0743@163.com

通讯作者:
徐金明（1963-），男，博士，教授，博士生导师，主要从事工程地质与岩土工程的教学与科研工作。E-mail： xjming@163.com

中图分类号: TU46+3
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出版历程
- 收稿日期: 2022-08-11
- 修回日期: 2022-11-07
- 刊出日期: 2023-09-19

Deformation characteristics of deep foundation pit with suspended waterproof curtain during excavation

XIANG Zhufeng,
XU Jinming^,

Department of Civil Engineering, Shanghai University, Shanghai　200444, China

摘要

摘要: 降水条件对基坑开挖的变形特性具有重要影响。为了研究悬挂式止水帷幕结合承压非完整井组成的墙井系统条件下基坑开挖过程中的变形问题，以某悬挂式止水帷幕深基坑为例，通过定义降水井和地表渗流边界条件建立了考虑分级降水和基坑开挖实际工况的三维流固耦合有限元数值分析模型，使用现场监测数据与数值模拟结果互相验证的方法研究了悬挂式止水帷幕情况下基坑开挖过程中地下连续墙变形和地表沉降的变化特征，对比分析了悬挂式止水帷幕和落底式止水帷幕条件下的地表沉降。结果表明：在不同分级降水情况下，降水深度初次达到场地第一承压水含水层降水期间产生的地下连续墙水平位移增量最大，地表沉降也主要在这一期间产生；悬挂式止水帷幕情况下的地表沉降最大值约为落底式止水帷幕的2.7倍，最大值位置距地下连续墙边缘的距离比落底式止水帷幕大0.85 m；地下连续墙水平位移峰值处，降水期间产生的位移占28%，地表沉降峰值处，降水期间产生的沉降占49%；使用悬挂式止水帷幕时，距地下连续墙边缘12倍开挖深度处，地表沉降与地表沉降峰值的比值为0.1、该距离比落底式止水帷幕大13 m左右。研究成果对确定深基坑降水方案、保证深基坑开挖施工安全具有一定的参考价值。
- 悬挂式止水帷幕 /
- 分级降水 /
- 深基坑 /
- 基坑变形
Abstract: Dewatering conditions have an important influence on the deformation characteristics of foundation pit excavation. In order to study the deformation problem during foundation pit excavation under the condition of a wall-well system consisting of suspended waterproof curtain combined with confined partially penetrating well, this study takes a deep foundation pit with suspended waterproof curtain as an example, uses the finite element numerical analysis to establish a 3D fluid-solid interaction model, and takes into account the actual working conditions of graded dewatering during the pit excavation by defining the seepage boundary conditions of the dewatering well and the surface. The monitoring data and simulation results are combined to explore the variation features of underground diaphragm wall deformation and surface settlement with suspended waterproof curtain, and the surface settlement under the conditions of suspended waterproof curtain and drop waterproof curtain is further compared and analyzed. The results show that in dewatering process of the foundation pit at all levels, the horizontal displacement increment of the underground diaphragm wall is the greatest with the most of the surface subsidence as the dewatering depth reaches the first confined aquifer. The maximum surface settlement generated by foundation pit with suspended waterproof curtain is about 2.7 times that with drop waterproof curtain, with the greater 0.8 m of the maximum surface settlement location. At the peak of horizontal displacement of underground diaphragm wall, the displacement during dewatering accounts for 28%, and at the peak of surface settlement, the settlement during dewatering accounts for 49%. When the suspended waterproof curtain is used at 12 times the excavation depth from the edge of the diaphragm wall, the ratio of surface settlement to the peak of surface settlement is 0.1, which is about 13 m greater than that of the drop waterproof curtain. The research results are of a reference value for determining the deep foundation pit dewatering scheme and ensuring the safety of deep foundation pit excavation construction.
- suspended waterproof curtain /
- graded dewatering /
- deep foundation pit /
- foundation pit deformation

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图 1 工程平面图

Figure 1. Project plan

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图 2 本文的承压非完整井＋悬挂式止水帷幕方案

Figure 2. Schemes of partially confined penetrating well plus suspended curtain proposed in this study

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图 3 基坑降水井及监测点布置

Figure 3. Layout of foundation pit dewatering wells and monitoring points

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图 4 悬挂式止水帷幕布置

Figure 4. Suspended curtain arrangement

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图 5 基坑降水开挖三维流固耦合模型

Figure 5. 3D fluid-structure coupling model of foundation pit dewatering and excavation

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图 6 基坑降水渗流场

Figure 6. Foundation pit dewatering seepage field

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图 7 监测井SWY49水位随时间的变化

Figure 7. Changes in water level at monitoring well SWY49 with time

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图 8 基坑竣工后地下连续墙水平位移与降水和开挖关系

Figure 8. Relationship between the horizontal displacement of diaphragm wall and dewater and excavation after foundation pit completion

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图 9 不同施工阶段的地下连续墙水平位移增量

Figure 9. Horizontal displacement increments of diaphragm wall caused by various construction stages

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图 10 基坑竣工后地表沉降与降水和开挖关系

Figure 10. Relationship between the surface settlement and dewater and excavation after foundation pit completion

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图 11 各施工阶段引起的地表沉降增量

Figure 11. Incremental surface settlement caused by each construction phase

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图 12 基坑竣工后地表沉降归一化曲线

Figure 12. Normalized surface settlement curve after foundation pit completion

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表 1 研究区土层性质

Table 1. Characteristics of the soil layers in the study area

土层特征	土层名称	含水层名称	厚度/m
①₃	素填土	潜水层	2.63
③₂	粉质黏土	弱透水层	4.30
④₁	粉质黏土	弱透水层	4.50
④₂	粉砂夹粉土	承压水层	6.30
⑤₁	粉质黏土夹粉砂	弱透水层	6.20
⑤₂	粉砂夹粉质黏土	承压水层	5.40
⑦₁	粉质黏土	弱透水层	5.67

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表 2 各土层物理力学性质参数

Table 2. Physical and mechanical parameters of the soil layers

各土层性质	ρ/（g∙cm⁻³）	λ	Μ	e₁	κ	K_V/（m∙d⁻¹）	K_H/（m∙d⁻¹）	υ
①₃	1.90	0.077 0	0.570	0.811	0.009 0	3.89×10⁻³	5.84×10⁻³	0.33
③₂	1.94	0.055 3	0.979	0.822	0.006 5	5.62×10⁻³	8.43×10⁻³	0.33
④₁	1.89	0.044 5	0.979	0.696	0.005 2	8.21×10⁻³	1.23×10⁻²	0.33
④₂	1.91	0.029 3	1.202	0.640	0.003 4	1.73	2.60	0.23
⑤₁	1.89	0.032 0	0.900	0.611	0.003 7	5.18×10⁻²	7.77×10⁻²	0.33
⑤₂	1.94	0.019 1	1.382	0.585	0.002 2	2.59	3.89	0.23
⑦₁	1.90	0.030 5	0.900	0.676	0.003 5	5.00×10⁻³	7.50×10^-3	0.38
注：ρ为密度；λ为土体压缩指数；Μ为土体应力比；e₁为压力为1 kPa时土体的孔隙比；κ为土体回弹指数；K_V为土体竖直渗透系数； K_H为土体水平渗透系数；υ为泊松比。

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表 3 围护结构及降水井材料参数

Table 3. Material parameters of the retaining structure and dewatering well

参数	ρ/（g∙cm⁻³）	E/MPa	υ
地下连续墙	2.42	31 500	0.20
混凝土支撑	2.36	30 000	0.20
钢支撑	7.85	200 000	0.20
降水井	7.85	210 000	0.20
注：E为弹性模量。

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