细粒迁移及组构变化对黏土渗透性影响的试验研究

为进一步探究水化学环境下土体渗透性的变化规律及作用机理,对饱和重塑压实黏土样在不同水化学条件及渗流路径下进行了一系列变水头渗透试验,分析了不同浓度的NaCl溶液在不同渗流路径下对饱和黏土渗透性的影响。结果表明：不同干密度试样的渗透性随浓度增加展现出较大的差异,干密度为1.40 g/cm³时,渗透系数呈先升后降,而干密度为1.50 g/cm³时,渗透系数不断降低;逆转渗流方向,试样渗透系数发生突变;孔隙盐溶液浓度周期性变化,试样渗透性不可逆。基于核磁共振（NMR）分析技术,测试了土体内部孔隙结构分布随孔隙盐溶液浓度的变化。最后基于上述试验结果从细粒迁移产生的孔隙堵塞效应和组构改变引起的孔隙封闭效应两个方面,解释了孔隙盐溶液浓度变化对黏土渗透性的影响。

Experimental study on effects of fine particle migration and fabric change on permeability of clay

The permeability of soils is of importance in the engineering design and construction. For the clayey soils, the change law and mechanism of permeability in hydrochemical environment are not clear due to the complex physicochemical interactions between the clay minerals and pore water. To explore the effects of salt solution on the permeability, a series of variable head permeability tests are performed on the remolded clay samples. The results show that the variation of the permeability with the concentration depends upon the dry density. For the samples with the dry density of 1.4 g/cm³, the permeability increases firstly and then decreases as the concentration increases. However, the permeability of samples with the dry density of 1.5 g/cm³ decreases continuously. When the direction of seepage is reversed, the permeability of the samples changes drastically. The change of permeability is irreversible under the periodical variation of the pore water concentration. In addition, the measurement of the variation of pore structure in the soils with the salt solution concentration is conducted by the nuclear magnetic resonance (NMR) analysis. Based on the above experimental results, the effects of salt solution concentration on the clay permeability are explained from two aspects: pore plugging effects caused by fine particle migration and pore sealing effects caused by fabric change.