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浙江大学学报(工学版)  2020, Vol. 54 Issue (7): 1380-1389    DOI: 10.3785/j.issn.1008-973X.2020.07.017
交通工程、水利工程、土木工程     
软土地层中压入式沉井下沉的土塞效应及其影响
易琼1(),廖少明1,*(),朱继文2,徐伟忠2
1. 同济大学 地下建筑与工程系,上海 200092
2. 上海城建市政工程(集团)有限公司,上海 200065
Effect of soil plugging during press-in caisson sinking in soft ground
Qiong YI1(),Shao-ming LIAO1,*(),Ji-wen ZHU2,Wei-zhong XU2
1. Department of Geotechnical Engineering, Tongji University, Shanghai 200092, China
2. Shanghai Urban Construction Municipal Engineering (Group) Limited Company, Shanghai 200065, China
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摘要:

针对软土地层中压入式沉井的下沉稳定性控制问题,基于土塞形成机理推导出土塞高度的计算表达式,采用耦合欧拉-拉格朗日法(CEL)模拟沉井的动态压入过程,分析下沉中的土塞演化过程及土体应力、应变场,探讨土塞效应对沉井侧摩阻力和刃脚阻力的影响. 结果表明:在软土地层中,土塞高度的计算表达式能够较准确地得到下沉时的井内土塞高度;沉井压入下沉时土塞效应逐渐增大,在下沉深度约为25 m时变化趋势放缓,土塞率(PLR)约为0.56,土塞增量填充率(IFR)约为0.41,土塞为不完全闭塞;土塞效应引起的井内土体水平和竖向应力激增及土体等效塑性应变主要集中于有效土塞高度范围内;土塞效应会使沉井侧摩阻力尤其是内壁侧摩阻力显著增大;土塞效应会使沉井刃脚阻力增大,尤其在软弱地层中最明显.

关键词: 压入式沉井软土地层土塞效应有效土塞高度耦合欧拉-拉格朗日法(CEL)    
Abstract:

An analytical calculation formula of soil plug’s height was deduced based on the generating mechanism of soil plug in order to analyze the control of press-in caisson’s sinking stability in soft ground. Then the coupled Eulerian-Lagrangian (CEL) method was used to simulate the sinking process of a press-in caisson. The influence of soil plugging effect on lateral friction force and blade feet resistance force was discussed based on the analysis of the developing process of soil plug and stress and strain field of soil. Results show that the analytical calculation formula can precisely predict the soil plug’s height in soft ground. The soil plugging effect gradually increases during the caisson’s press-in sinking procedure, but the pace of change slows down around the depth of 25 m. The plug length ratio (PLR) is about 0.56 at the end of sinking, and the incremental filling ratio (IFR) is about 0.41, which means that the soil plug is still incomplete occlusive. The increase in horizontal and vertical soil stress as well as the equivalent plastic strain caused by soil plugging effect mainly concentrated in the range of the effective soil plug’s height. Then the lateral friction force increases, but lateral friction force of inner wall grows more remarkable compared with outer wall. The blade feet resistance force increases owing to soil plugging effect, and the increase becomes significant especially in soft ground.

Key words: press-in caisson    soft ground    soil plugging effect    effective soil plug’s height    coupled Eulerian-Lagrangian (CEL)
收稿日期: 2019-06-09 出版日期: 2020-07-05
CLC:  U 445  
基金资助: 国家“973”重点基础研究发展规划资助项目(2015CB057806);上海市科委资助项目(18DZ1205404)
通讯作者: 廖少明     E-mail: yiqiong@tongji.edu.cn;liaosm@126.com
作者简介: 易琼(1996—),男,硕士生,从事盾构隧道及沉井等地下工程的研究. orcid.org/0000-0003-1425-6640. E-mail: yiqiong@tongji.edu.cn
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引用本文:

易琼,廖少明,朱继文,徐伟忠. 软土地层中压入式沉井下沉的土塞效应及其影响[J]. 浙江大学学报(工学版), 2020, 54(7): 1380-1389.

Qiong YI,Shao-ming LIAO,Ji-wen ZHU,Wei-zhong XU. Effect of soil plugging during press-in caisson sinking in soft ground. Journal of ZheJiang University (Engineering Science), 2020, 54(7): 1380-1389.

链接本文:

http://www.zjujournals.com/eng/CN/10.3785/j.issn.1008-973X.2020.07.017        http://www.zjujournals.com/eng/CN/Y2020/V54/I7/1380

图 1  沉井结构图
图 2  施工场地平面图
土层名称 d/m $\gamma $/(kN·m?3 直剪 ${E_{{\rm{s}}1 {\text{-}} 2}}$/MPa ${f_{\rm{k}}}$/kPa ${f_{{\rm{ak}}}}$/kPa
$c$/kPa $\varphi $/(°)
砂垫层 3.1 20.0 10.0 30.0 13.8 20 120
1淤泥 12.7 15.0 8.9 8.2 1.45 10 40
2淤泥 10.0 15.7 11.3 9.2 2 11 50
11粉质黏土 3.5 19.3 25.1 19.4 5.73 21 140
12粉质黏土 6.0 17.7 14.6 29.9 8.35 23 150
2黏土 15.2 17.8 25.6 11.1 3.93 18 120
2黏土 19.5 18.1 29.4 14.2 4.96 20 130
表 1  土层的主要物理力学参数
图 3  施工场地地质剖面图
图 4  井内土塞受力分析图
图 5  CEL有限元模型示意图
土层 $\gamma $/(kN·m?3) $c$/kPa $\varphi $/(°) $\;\beta $/(°) $\kappa $ $\psi $/(°) ${\sigma _{\rm{c}}}$/kPa ${E_{{\rm{s}}1 - 2}}$/kPa E/kPa $\nu $
砂垫层 20.0 10.0 30 50.2 0.778 0 34.64 13 800 41 400 0.20
淤泥层 15.3 10.0 8.6 17.5 0.905 0 23.25 1 692 5 076 0.49
黏土层 18.0 25.4 15.9 31.1 0.833 0 67.29 5 127 15 381 0.49
表 2  CEL法的土体计算参数
图 6  数值模型与现场试验得到的端阻对比
图 7  土塞率、土塞增量填充率随下沉深度的变化
图 8  下沉过程中的土体速度场分布
图 9  下沉过图程中的土体颗粒变形趋势
图 10  典型水平应力云图
图 11  典型竖向应力云图
图 12  等效塑性应变云图
图 13  内壁侧摩阻力随下沉深度的变化
图 14  外壁侧摩阻力随下沉深度的变化
图 15  刃脚阻力随下沉深度的变化
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