初始孔隙比对高吸力下非饱和土土水特性的影响

陈嘉伟; 李泽; 韩哲; 高游; 熊勇林; 丁瑞旋

doi:10.16030/j.cnki.issn.1000-3665.202106043

初始孔隙比对高吸力下非饱和土土水特性的影响

宁波大学土木与环境工程学院, 浙江宁波　315211

基金项目: 浙江省省属高校基本科研业务费专项资金项目（SJLY2022007）；浙江省新苗人才计划项目（2020R405031）；浙江省自然科学基金项目（LY19E080012）；

详细信息

作者简介: 陈嘉伟（2000-），男，本科生，主要从事非饱和土持水特性研究。E-mail：912817583@qq.com

通讯作者: 高游（1989-），男，博士，副教授，主要从事非饱和土力学研究。E-mail：gaoyou@nbu.edu.cn

中图分类号: TU411.3

收稿日期: 2021-06-18

修回日期: 2021-10-10

刊出日期: 2022-07-25

Effect of initial void ratio on the soil water characteristics of unsaturated soil at high suctions

School of Civil and Environmental Engineering, Ningbo University, Ningbo, Zhejiang　315211, China

More Information

Corresponding author: GAO You, gaoyou@nbu.edu.cn

Received Date: 18 June 2021

Revised Date: 10 October 2021

Publish Date: 25 July 2022

摘要

摘要:
在我国西北干旱半干旱地区，处于高吸力范围内的非饱和土广泛存在于各种岩土工程中。非饱和土土水特性的研究是非饱和土渗流、强度与变形研究的基础。为研究高吸力下不同初始孔隙比非饱和土的土水特性，以一种粉土试样作为研究对象，采用饱和盐溶液蒸汽平衡法控制土试样的吸力，利用阿基米德原理量测不规则土试样的体积，通过修正的Van-Genuchten模型模拟试样高吸力下不同初始孔隙比的土水特征曲线。结果表明：（1）将土水特征曲线表示为含水率与吸力的关系时，初始孔隙比对土水曲线几乎没有影响，表明高吸力下非饱和土的土水特性主要与吸附水的含量相关；（2）以Van-Genuchten模型为基础，发现考虑初始孔隙比影响的土水特征曲线方程无法准确拟合高吸力下的土水曲线；故在此基础上方程引入修正项，得到一个能够较好地模拟高吸力下非饱和土土水特征曲线的方程；（3）将该方程应用于非饱和土相对渗透系数的模拟，可得到考虑初始孔隙比影响的非饱和土相对渗透系数方程。结合相关实测数据加以验证，其预测结果与试验数据吻合较好，说明提出的土水特征曲线方程具有一定的可靠性。
- 非饱和土 /
- 高吸力 /
- 初始孔隙比 /
- 土水特征曲线
Abstract:
In arid and semi-arid regions, such as in northwestern China, unsaturated soils at high suction or over a wide suction range are widespread in various geotechnical designs. Studies of the soil water retention behavior are fundamental to a comprehensive understanding of the water flow, deformation processes, and shears strength for unsaturated soils. To investigate the soil water retention behavior of a silt over a high suction range, the suction is imposed on silt specimens using the vapor equilibrium technique, and the volume of irregular soil sample is measured using the Archimedean method. The soil water characteristic curves (SWCCs) with different initial void ratios at high suctions were simulated by the modified Van Genuchten’s model. The results show that (1) SWCCs in terms of water content versus suction relation with different initial void ratios are independent of the initial void ratio at high suctions. That is, soil water retention at high suctions is mainly related to adsorbed water content. (2) It was found that the fitting results of the existing equation based on Van Genuchten’s model can not accurately simulate the soil water retention behavior over a high suction range. A modified soil water characteristic equation is proposed by introducing a correcting function into the equation. (3) A modified relative permeability coefficient equation is proposed and it can be applied to predict the relative permeability coefficient with different initial void ratios. The predicted results are in good agreement with the measured values.
- unsaturated soil /
- high suctions /
- initial void ratio /
- SWCC

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图 1 制样模具及试样

Figure 1.

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图 2 蒸汽平衡法的密闭容器

Figure 2.

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图 3 土样体积测量装置

Figure 3.

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图 4 高吸力下不同初始孔隙比土样的土水特征曲线

Figure 4.

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图 5 修正后的方程拟合土水特征曲线结果

Figure 5.

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图 6 修正后的方程拟合土水特征曲线结果

Figure 6.

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图 7 不同初始孔隙比粉砂壤土土水特性的模拟结果

Figure 7.

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图 8 不同初始孔隙比的粉砂壤土相对渗透系数预测

Figure 8.

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表 1 试验粉土基本物理指标

Table 1. Physical indices of silt

指标	比重	液限 /%	塑限 /%	最优含水率/%	最大干密度/（g·cm⁻³）
取值	2.70	28.73	18.96	15.2	1.81

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表 2 饱和盐溶液及对应吸力值（20 °C）

Table 2. Saturated salt solution and corresponding suction

饱和盐溶液	总吸力/MPa
LiCl·H₂O	286.70
MgCl₂·6H₂O	149.51
NaBr	71.12
NaCl	38.00
KCl	21.82
KNO₃	7.48
K₂SO₄	3.29

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表 3 典型的土水特征曲线方程

Table 3. Typical soil water characteristic curve equations

编号	参考文献	数学表达式	参数意义
1	Brooks 等^[18]		a为进气值/kPa； m为拟合参数
2	Van Genuchten^[19]		a、m和n为拟合参数
3	Fredlund 等^[20]		e为自然底数； ψ_re为残余吸力值/kPa； a、m和n为拟合参数
4	Gardner^[21]		a和n为拟合参数
5	Romero 等^[22]		ψ_re为残余吸力值/kPa； a、m和n为拟合参数

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表 4 不同类型土的粒组成分

Table 4. Particle size composition of different soils

土的类型	砂粒质量分数/%	粉粒质量分数/%	黏粒质量分数/%
南阳膨胀土^[10]	6	64	30
粉质黏土^[4]	28	42	30
砂质粉土^[24]	45	49	6

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