Abbaslou Hanie, Hadifard Hojat, Ghanizadeh Ali Reza
Civil Engineering Department, Sirjan University of Technology, Sirjan, 7813733385, Iran.
Hydraulic Structures, Civil Engineering Department, Sirjan University of Technology, 7813733385, Sirjan, Iran.
Heliyon. 2020 Feb 24;6(2):e03462. doi: 10.1016/j.heliyon.2020.e03462. eCollection 2020 Feb.
Dispersivity of clay soils is one of the most important issues that should be considered in civil engineering projects. Dispersive soils are clay soils that are easily washed in water with low concentrations of salt; these clay soils usually contain high levels of sodium ions in their adsorption cation sites. Kaolin, sepiolite (fibrous clay), and bentonite soils are among the most important and useful industrial materials. Therefore, in this study, these three clay soils were selected to investigate dispersivity potential by adding 4% of dispersive materials (Sodium hexametaphosphate) and performing shear strength, crumb, double hydrometer, pinhole tests, and chemical experiments. Results indicated a change in the Sodium Adsorption Ratio (SAR) in the following order: kaolin > sepiolite > bentonite. Stabilization practices using chemical methods were done after performing soil divergence with sodium hexametaphosphate. CaCl, CaSO, AlCl, and Al (SO) were used for chemical stabilization to assess the effect of ion valence on soil improvement parameters. Results obtained for chemical properties showed that, stabilization potential was in the following order: kaolin > sepiolite > bentonite; meaning that clay soils with lower cation exchange capacity have more remediation potential and are more susceptible to dispersion. The role of calcium and aluminum cations was prominent in improving mechanical and dispersivity properties, respectively. In general, further dispersion potential of clays in the same Na concentration was found to be related to a decrease in the cation exchange capacity, specific surface area, and plastic index. Soil dispersion was directly associated with diffuse double layer and electrostatic forces while; soil strength parameters were mainly dependent on cementation and connection of soil particles to each other. Consequently, it was observed that, clay soils with suitable engineering properties (higher strength and compaction or lower Atterberg limits) are more sensitive to dispersion compared to other types of clay with higher CEC and plasticity values.
粘性土的分散性是土木工程项目中应考虑的最重要问题之一。分散性土是指在低盐浓度水中容易被冲刷的粘性土；这些粘性土在其吸附阳离子位点通常含有高浓度的钠离子。高岭土、海泡石（纤维状粘土）和膨润土是最重要且有用的工业材料。因此，在本研究中，选择这三种粘性土，通过添加4%的分散材料（六偏磷酸钠）并进行剪切强度、碎块、双比重计、针孔试验和化学实验来研究其分散性潜力。结果表明钠吸附比（SAR）的变化顺序为：高岭土＞海泡石＞膨润土。在用六偏磷酸钠使土壤分散后，采用化学方法进行稳定化处理。使用氯化钙、硫酸钙、氯化铝和硫酸铝进行化学稳定化处理，以评估离子价态对土壤改良参数的影响。化学性质的结果表明，稳定化潜力顺序为：高岭土＞海泡石＞膨润土；这意味着阳离子交换容量较低的粘性土具有更大的修复潜力，且更易分散。钙和铝阳离子分别在改善力学性能和分散性方面发挥着显著作用。总体而言，发现在相同钠浓度下，粘土的进一步分散潜力与阳离子交换容量、比表面积和塑性指数的降低有关。土壤分散性与扩散双电层和静电力直接相关，而土壤强度参数主要取决于土壤颗粒之间的胶结和连接。因此，观察到具有合适工程性质（较高强度和压实度或较低阿太堡界限） 的粘性土比其他具有较高阳离子交换容量和塑性值的粘土类型对分散更敏感。
