考虑泊松效应的流泥轴对称真空过滤理论

蔡袁强; 叶晓倩; 史吏

doi:10.11779/CJGE20231124

考虑泊松效应的流泥轴对称真空过滤理论 English Version

浙江工业大学土木工程学院, 浙江杭州 310014

基金项目:

离岸岛群深厚软土地基交通基础设施建设关键技术 2023YFB2604200

国家自然科学基金项目 52278377

国家自然科学基金项目 U2006225

浙江省自然科学基金项目 LZ22E080009

详细信息

作者简介:
蔡袁强(1965—)，男，博士，教授，主要从事地基处理、基础工程学、土动力学等方面的教学和科研工作。E-mail: caiyq@zju.edu.cn

通讯作者:
史吏, E-mail：418194187@qq.com

中图分类号: TU432
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出版历程
- 收稿日期: 2023-11-23
- 网络出版日期: 2024-04-18
- 刊出日期: 2025-01-31

Radial filtration model for prefabricated vertical drain treatment of slurry considering Poisson's effects

College of Civil Engineering, Zhejiang University of Technology, Hangzhou 310014, China

摘要

摘要: 真空预压处理流泥地基时，仅排水板附近的土体得到明显加固，以排水板为轴线形成一个凸出地表的“土柱”。土柱作为流泥地基真空预压处理的特有现象，导致流泥地基淤堵严重、处理效果差。根据流泥固液两相的连续、运动、平衡以及土柱移动边界方程，并考虑土柱土体泊松效应，在柱坐标系下建立了流泥轴对称真空过滤模型，获得了流泥地基真空预压过程中的土柱生长规律和土柱淤堵性状，并与PIV试验进行了对比验证。结果表明：土柱内渗透系数降幅高达97%，致密土柱是淤堵的本质；泊松效应和真空荷载幅值对土柱半径以及流泥固结效果的影响十分明显；低幅值真空荷载有利于形成半径小且较为疏松的淤堵区，从而缓解淤堵性状。
- 流泥 /
- 真空预压 /
- 过滤 /
- 土柱 /
- 淤堵 /
- 固结 /
- 泊松效应
Abstract: During the vacuum preloading treatment of slurry ground, the significant improvement is only observed in the soil adjacent to the prefabricated vertical drain (PVD), resulting in the formation of a protruding "soil column" with the PVD as its axis. The presence of soil column, as a unique phenomenon of slurry ground pre-treatment, leads to severe clogging and ineffective treatment results. An axisymmetric vacuum filtration model is established in the coordinate system using the continuity, kinematic and equilibrium equations for both liquid and solid phases of slurry. The moving boundary condition and Poisson's effects associated with the soil column are also incorporated. The growth pattern and clogging behavior of soil columns are investigated through the model and verified by comparing the predicted results with the particle image velocity (PIV) ones. The results show that reduction of permeability coefficient within the soil column is up to 97%, indicating that the dense soil column is the essence of clogging. Furthermore, notable influences of the Poisson's effects and negative pressure on the growth and compression behavior of the soil column are observed. The low amplitude negative pressure promotes formation of the relatively small loose soil columns, thereby mitigating the clogging behavior.
- slurry /
- vacuum preloading /
- filtration /
- soil column /
- clogging behavior /
- consolidation /
- Poisson's effect

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图 1 平面过滤过程及轴对称过滤示意图

Figure 1. (a)unidimensional coordinate; (b) cylindrical coordinate

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图 2 流泥轴对称过滤模型示意图

Figure 2. Schematic diagram of formation and growth

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图 3 土柱内土单元应力平衡分析

Figure 3. Stress equilibrium analysis for soil element within soil column

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图 4 流泥真空预压工况

Figure 4. Operating conditions of vacuum preloading for slurry

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图 5 节点划分

Figure 5. Distribution of grid points

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图 6 土柱半径随时间变化

Figure 6. Variation of radius of soil column with time

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图 7 孔压消散随时间变化

Figure 7. Variation of pore water dissipation with time

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图 8 泥浆液面高度随时间变化曲线

Figure 8. Heights of slurry surface versus time

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图 9 真空荷载幅值对土柱大小的影响

Figure 9. Effects of negative pressure on size of soil column

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图 10 径向移动边界位置随时间变化曲线

Figure 10. Radial moving boundary versus time

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图 11 土柱内部淤堵性状

Figure 11. Internal clogging characteristics of soil column

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图 12 淤堵区半径随时间变化曲线

Figure 12. Radii of clogging column

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图 13 排水板滤膜处表观流速随时间变化曲线

Figure 13. Temporal variation in apparent flow velocity of water drained through PVD membrane

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图 14 土柱半径随时间变化

Figure 14. Variation of radius of soil column with time

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图 15 孔压消散随时间变化：r=25 mm

Figure 15. Variation of pore water dissipation with time: r=25 mm

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图 16 孔压消散随时间变化：r=50 mm

Figure 16. Variation of pore water dissipation with time: r=50 mm

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表 1 流泥土样基本参数

Table 1 Physical and mechanical parameters of main soils

物理参数	相对质量密度 ${G_{\text{s}}}$	液限 ${w_{\text{L}}}$ /%	塑限 ${w_{\text{P}}}$ /%	平均粒径 ${d_{50}}$ / ${\text{μ m}}$
台州流泥	2.67	40	23	11
温州流泥	2.68	53	32	5

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表 2 计算参数取值

Table 2 Parameters used in PIV validation of proposed theory

土样	本构参数					真空荷载 ${P_0}$ /kPa	PVD流动阻力 $R$ /m^-1	PVD等效半径 ${r_{\text{w}}}$ /m	泥浆初始高度 ${H_0}$ /m	等效影响区半径 S/ m
土样	$\varepsilon _{\text{s}}^{\text{0}}$	$\delta$	$\beta$	${p_{\text{a}}}$ /kPa	${K_0}$ /10^-15 m²	真空荷载 ${P_0}$ /kPa	PVD流动阻力 $R$ /m^-1	PVD等效半径 ${r_{\text{w}}}$ /m	泥浆初始高度 ${H_0}$ /m	等效影响区半径 S/ m
台州流泥	0.3675	0.8548	0.1067	1.3	9.283	80	21.8	0.033	0.3	0.267
温州流泥	0.3832	0.6596	0.076	1.3	3.601	80	100	0.033	0.3	0.267

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