Soil-water characteristic curve reflects water retention behavior of unsaturated soil mass. Particle size and mineral composition can influence water retention behavior of soil mass significantly. To discuss effects of particle size and solution leaching on water retention behavior of ion-absorbed rare earth, soil-water characteristic tests of samples with different particle sizes before and after the solution leaching were carried out by using a pressure plate instrument. Soil-water characteristic curves during drying and wetting were analyzed. A fitting analysis on test data was implemented by the Fredlund&Xing 3 parameter model, the Fredlund&Xing 4 parameter model, and the Van Genuchten model to discuss variation laws of soil-water characteristic parameters in different models. Effects of particle size and solution leaching on water retention behavior of ion-absorbed rare earth as well as action mechanism were investigated. Results demonstrate that given the same matric suction, soil water content decreases gradually with the increase of particle size and content of coarse particles, thus decreasing water retention capacity of soil accordingly. Given the same volumetric water content, matric suction is inversely proportional to particle size. During drying and wetting, the amplitude of variation decreases gradually with the increase of particle size and content of coarse particles. The soil water content after solution leaching is smaller than that before under the same matric suction, indicating that solution leaching can decrease water retention capacity of soil. This is mainly because thickness of the double diffuse layer and pore water pressure are increased as a response to the ion exchange, thus decreasing matric suction.

中文翻译：

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粒径和溶液浸出对离子吸收稀土保水行为的影响

土水特征曲线反映了非饱和土体的保水行为。颗粒大小和矿物成分可以显着影响土体的保水行为。为探讨粒径和溶液浸出对离子吸附稀土保水行为的影响，采用压板仪对溶液浸出前后不同粒径样品进行了土水特性测试。分析了干燥和润湿过程中的土壤-水特征曲线。通过Fredlund&Xing 3参数模型、Fredlund&Xing 4参数模型和Van Genuchten模型对试验数据进行拟合分析，讨论不同模型中土-水特征参数的变化规律。研究了粒径和溶液浸出对离子吸附稀土保水行为的影响及作用机理。结果表明，在相同的基质吸力下，土壤含水量随着粒径和粗颗粒含量的增加而逐渐降低，从而降低土壤的保水能力。给定相同的体积含水量，基质吸力与颗粒尺寸成反比。在干燥和润湿过程中，变化幅度随着粒径和粗颗粒含量的增加而逐渐减小。在相同基质吸力下，溶液淋洗后的土壤含水量小于前，表明溶液淋洗会降低土壤的保水能力。