为准确测试贵阳红黏土在不同介质环境的分散状况,同时考虑贵阳红黏土特殊的微观结构对粒度分布的影响,分别采用机械研磨法、超声波法和化学分散法分散后进行粒度分析试验,研究贵阳红黏土粒度分布规律及形成原因。试验表明:利用化学试剂作为土体颗粒分散剂较机械研磨和超声波对土体颗粒分散效果明显提高。进一步采用5种化学试剂对贵阳红黏土进行颗粒分散,发现六偏磷酸钠作为一种强碱弱酸盐取得最佳分散效果,最后以浓度、温度及试剂量为影响因子,找出最适宜贵阳红黏土的分散条件。结果表明六偏磷酸钠溶液在浓度为2%、剂量为10~15 mL和温度控制在40 ℃左右时分散效果最优。在上述试验基础上,进一步研究贵阳红黏土分散机理,认为贵阳红黏土微观结构单元间通过游离氧化铁接触和填充形成特殊的空间结构形式——胶结粒团,游离氧化铁自身活性强,易受环境条件变化发生不同程度水解变化,影响胶粒集团的牢固程度,是土体表现出不同分散性的关键因素。

The dispersion status of Guiyang red clay in different media environment was accurately tested in the present research. In the light of the effect of Guiyang red clay’s special microstructure on particle size distribution, particle size analysis test was carried out using mechanical grinding method, ultrasonic method, and chemical dispersion method, respectively, to study the particle size distribution law. Results unveil that the dispersion of soil particles treated with chemical reagent is better than that with mechanical grinding or ultrasonic wave. Five types of chemical reagents were further used for particle dispersion, among which sodium hexametaphosphate ((NaPO₃)₆), as a strongly alkaline and weakly acid salt, has the optimum dispersion effect. Moreover, concentration, temperature, and test dose were selected as influential factors to obtain the most favorable dispersion conditions for Guiyang red clay: (NaPO₃)₆ solution with a concentration of 2% and dose of 10-15 mL at a temperature around 40 ℃. On such basis, the dispersion mechanism of Guiyang red clay was expounded: cemented agglomerations, a particular spatial structure, were formed among the micro-structural cells of Guiyang red clay via free iron oxide. Free iron oxide is of strong activity and is prone to be hydrated under varying environment, thus affecting the fastness of cemented agglomerations, and therefore is a key factor leading to different dispersion effects.