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既有地下结构水-土阻隔效应对基坑抽水引发地层变形影响机制

薛秀丽, 廖欢, 曾超峰, 刘运思, 曾兴

薛秀丽, 廖欢, 曾超峰, 刘运思, 曾兴. 既有地下结构水-土阻隔效应对基坑抽水引发地层变形影响机制[J]. 岩土工程学报, 2023, 45(1): 103-111. DOI: 10.11779/CJGE20211393
引用本文: 薛秀丽, 廖欢, 曾超峰, 刘运思, 曾兴. 既有地下结构水-土阻隔效应对基坑抽水引发地层变形影响机制[J]. 岩土工程学报, 2023, 45(1): 103-111. DOI: 10.11779/CJGE20211393
XUE Xiuli, LIAO Huan, ZENG Chaofeng, LIU Yunsi, ZENG Xing. Barrier effects of existing underground structures on deformation of strata induced by dewatering of foundation pits[J]. Chinese Journal of Geotechnical Engineering, 2023, 45(1): 103-111. DOI: 10.11779/CJGE20211393
Citation: XUE Xiuli, LIAO Huan, ZENG Chaofeng, LIU Yunsi, ZENG Xing. Barrier effects of existing underground structures on deformation of strata induced by dewatering of foundation pits[J]. Chinese Journal of Geotechnical Engineering, 2023, 45(1): 103-111. DOI: 10.11779/CJGE20211393

既有地下结构水-土阻隔效应对基坑抽水引发地层变形影响机制  English Version

基金项目: 

国家自然科学基金项目 51978261

国家自然科学基金项目 51708206

湖南省教育厅项目 21A0290

湖南省教育厅项目 20A190

湖南省自然科学基金项目 2022JJ20023

湖南省科技创新计划项目 2022RC1172

详细信息
    作者简介:

    薛秀丽(1986—),女,博士,副教授,主要从事计算岩土力学方面的科研与教学工作。E-mail: xlxue@hnust.edu.cn

    通讯作者:

    曾超峰, E-mail: cfzeng@hnust.edu.cn

  • 中图分类号: TU463

Barrier effects of existing underground structures on deformation of strata induced by dewatering of foundation pits

  • 摘要: 当基坑邻近既有地下结构时,基坑降水引发的坑外地下水渗流与地层运动均会受到地下结构阻隔(阻水效应与阻土效应);因此,在有/无邻近地下结构情况下,降水引起的基坑变形规律应是不同的。依托实际基坑工程开展了现场抽水试验,实测得到了基坑抽水引起的坑外不同含水层水位变化及围挡与土体变形规律;并基此建立了考虑邻近地下结构阻隔影响的基坑抽水三维流固耦合数值模型,以基坑与邻近地下结构间距D、基坑降水深度Hd为变化参数,探究了邻近地下结构阻隔作用对基坑抽水引发基坑变形的影响。研究发现:当基坑与既有地下结构间距较小时(如D < 20 m),地下结构对基坑变形的阻隔作用以阻土效应为主,减小了坑外地面沉降(相对于无邻近地下结构而言,以下类同);当基坑与既有地下结构间距较大时(D > 20 m),地下结构对基坑变形的阻隔作用以阻水效应为主,增大了坑外地面沉降;而随着间距进一步增大(D > 40 m),阻水与阻土效应均逐渐减弱,坑外地面沉降分布向无地下结构时的情况趋近。基坑设计时应考虑邻近已有地下结构阻水、阻土效应耦合作用的影响以更准确地计算地层损失与围挡侧移,从而更好地优化基坑支护方案。
    Abstract: When a foundation pit is adjacent to the existing underground structures, the groundwater seepage and ground movement caused by dewatering will be blocked by the underground structures (i.e., the water- and soil-blocking effects). On this occasion, the deformations of the foundation pit with or without adjacent underground structures should be different. A pumping test is carried out based on an actual project, and the variations of water levels and the deformations of retaining walls and soils induced by pumping are measured. Thus, a three-dimensional fluid-solid coupling model is established to simulate the dewatering of a foundation pit considering the effect of adjacent underground structures. The distance between the foundation pit and the existing underground structures (D) and the dewatering depth (Hd) are selected as the two varying parameters in the numerical model to investigate the barrier effects of the adjacent underground structures on the deformation of the foundation pit caused by pumping. It is found that when D is small (e.g., D < 20 m), the soil-blocking effects play a leading role, reducing the ground settlement outside the pit (compared with the condition without the underground structures outside the pit). When D is large (e.g., D > 20 m), the water-blocking effects play a leading role, increasing the ground settlement outside the pit. However, with the further increase of D (e.g., D > 40 m), both the water- and soil-blocking effects gradually decrease, and the distribution of the ground settlement outside the pit tends to be similar to that without the underground structures. In the design of foundation pits, the coupling actions of the water- and soil-blocking effects of the adjacent underground structures should be considered so that more accurate calculation of the ground losses and wall deflections will be achieved, which is helpful to optimize the design of the foundation pits.
  • 图  1   基坑平面及测点布置

    Figure  1.   Plan view of the excavation and layout of instrumentation

    图  2   基坑北侧土层分布及物理力学参数

    Figure  2.   Typical soil profile at north side of foundation pit and basic properties of soils

    图  3   第二类模型有限元网格图

    Figure  3.   FE meshes of second type of model

    图  4   水位降深实测值与模拟值对比图

    Figure  4.   Comparison between computed and measured drawdowns

    图  5   最大围护结构实测值与模拟值对比图

    Figure  5.   Comparison between computed and measured wall deflections

    图  6   地面沉降实测值与模拟值对比图

    Figure  6.   Comparison between computed and measured ground settlements

    图  7   坑外水位降深沿深度方向变化

    Figure  7.   Distribution of groundwater drawdown outside pit along depth

    图  8   坑外地面沉降与围护结构侧移

    Figure  8.   Ground settlements outside pit and wall deflections

    图  9   围护结构两侧总压力差

    Figure  9.   Differences of total earth pressure at both sides of retaining walls

    图  10   车站前后方最大地面沉降与D/Hd的关系曲线

    Figure  10.   Relationship between δv1m, δv2m and D/Hd

    图  11   车站前后方最大地面沉降差值与D/Hd的关系曲线

    Figure  11.   Relationship between Δδvm and D/Hd

    图  12   最大围护结构侧移与D/Hd的关系曲线

    Figure  12.   Relationship between δhm and D/Hd

    图  13   坑外最大地面沉降和最大围护结构侧移关系

    Figure  13.   Relationship between δvm and δhm

    图  14   地面沉降面积和围挡侧移面积与D/Hd的关系曲线

    Figure  14.   Relationship among Asv, Aw and D/Hd

    图  15   不同工况下AsvAw的关系

    Figure  15.   Relationship between Asv and Aw

    表  1   数值模型中土层分布及物理力学参数

    Table  1   Distribution of soil strata and parameters used in model

    土层类型 层底深度/m γ/(kN·m-3) KH/(m·d-1) KV/(m·d-1) K0 c'/kPa φ'/(°) E/MPa
    粉质黏土 10.0 19.1 0.0300 0.0030 0.577 17 25 43.5
    粉质黏土 15.0 19.3 0.0250 0.0010 0.609 18 23 56.3
    粉土 19.0 20.2 0.2000 0.1000 0.441 10 34 137.6
    粉质黏土 22.0 19.9 0.0060 0.0010 0.562 19 26 118.6
    粉土 24.5 20.4 2.5000 0.5000 0.441 8 34 151.8
    粉土 29.5 20.6 1 0.2000 0.412 8 36 153.3
    粉质黏土 32.5 20.3 1 0.1600 0.562 17 26 128.0
    粉砂 35.5 20.6 3 0.6000 0.398 7 37 178.5
    粉质黏土 37.0 20.5 0.0200 0.0040 0.562 19 26 152.2
    粉土 41.0 20.7 3 0.9000 0.441 10 34 224.5
    粉质黏土 47.0 20.3 0.0005 0.0001 0.546 18 27 198.4
    粉砂 500. 20.6 3.5 1.5 0.384 7 38 257.0
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  • 收稿日期:  2021-11-22
  • 网络出版日期:  2023-02-03
  • 发布日期:  2021-11-22
  • 刊出日期:  2022-12-31

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