硫酸盐含量对黄土黏粒特性的影响研究

EFFECT OF SULFATE CONTENT ON CLAY CHARACTERISTICS OF LOESS

黏粒是黄土粒组的主要组成部分,也是影响黄土的最活跃部分,盐分的加入使得黄土中黏粒的团聚作用及物理力学性质都有明显的差异,这也决定了盐度在影响黏粒团聚的众多因子中占主导地位。以黄土为研究对象,探究盐分对黄土黏土颗粒团聚的影响和机理。本文在洗盐的基础上配制不同质量比(0、0.3%、0.5%、3.%、5.0%、8.0%)的人工硫酸盐盐渍土,基于粒度分析和界限含水率试验,研究硫酸盐对黏土颗粒的团聚作用的宏观表征,在击实试验的基础上结合XRD、SEM、EDS和BET研究硫酸盐含量对黏土颗粒团聚作用的微观结构和物理化学机理。试验表明:随着含盐量的增加,黏粒的含量减小,液限和塑性指数减小,塑限不变;含盐量大于0.3%时(即盐渍土)随着含盐量的增加,过多的硫酸钠无法溶解以晶体的形式析出,析出的晶体进一步吸收水分子最终形成芒硝晶体,体积会急剧增大,导致最大干密度一直减小,而强烈的水化作用则使最优含水率增大;硫酸盐对黏粒产生团聚作用,当含盐量增加时,芒硝晶体的衍射峰增强,团聚体的含量增多,比表面积减小,吸附能力减弱,扩散层压缩变薄,液限和塑性指数减小。

Clay is the main component of loess particle group, and also the most active part of loess activity. The addition of salt makes the agglomeration and physical and mechanical properties of clay in loess obviously different, which also means that salt content plays a dominant role in many factors affecting aggregation. Loess was taken as the research object. The influence and mechanism of salt on the aggregation of clay particles in loess was studied. The loess salted soil was taken as the research object to study the influence and mechanism of salt on the aggregation of clay particles in loess. In this paper, the artificial sulfate saline soils with different mass ratios(0, 0.3%, 0.5%, 3%, 5.0%, 8.0%) were prepared on the basis of salt washing. Based on the grain size analysis and Atterberg limits tests, the macroscopic token of sulfate on the aggregation of clay particles was studied. Based on the compaction test, the microstructure and physicochemical mechanisms of the aggregation of clay particles were studied by combining XRD,SEM,EDS and BET. The results show that with the increase of salt content, the content of clay decreases, the liquid limit and plasticity index decrease, and the plasticity limit remains unchanged. When the salt content is more than 0.3%(saline soil stage),with the increase of salt content, too much sodium sulfate can not be dissolved and precipitated in the form of crystal. The precipitated crystal further absorbs water molecules and finally forms mirabilite crystal, the volume can increase sharply, resulting in the decrease of the maximum dry density, and the strong hydration can increase the optimum water content. Due to the agglomeration of sulfate on clay, when the salt content increases, the diffraction peak of sodium sulfate crystal is enhanced, the content of aggregate increases, and the specific surface area decreases, and compressing and thinning the diffusion layer, which leads to a decrease in the liquid limit and plasticity index.