The Effect of Different Leaching on the Water Retention Characteristics of Ion-absorption Type Rare Earth
Soil-water characteristic curve is an important tool to study the water-holding characteristics of ion-absorption type rare earth.Through an indoor simulated leaching test and Geo-Experts pressure plate apparatus,the relationship between matric suction and water content under different leaching actions was obtained.By using the Van Genuchten model,the Fred-lund & Xing three-parameter model,and the Fredlund & Xing four-parameter model,respectively,the soil-water characteristic curves of different ion-absorption types of rare earth were studied,and the changing trend of each parameter of the three mod-els was analyzed.The results show that the Fredlund & Xing four-parameter model has the best effect for fitting the soil-water characteristic curve of ion-absorption type rare earth.According to the analysis of the water-holding characteristics of ion-ab-sorption type rare earth after the leaching action of different types of leaching solutions,the water holding capacity of the soil was most improved by pure water,followed by 3％magnesium sulfate solution and 3％ammonium sulfate solution.As the con-centration of the leaching solutions increased,the water holding capacity of the sample gradually decreased,and the concentra-tion decreased most significantly from 0 to 2％,Moreover,the significance levels of actors affecting the"hysteresis effect"of the soil-water characteristic curve were decreased from pure water,3％magnesium sulfate solution,to 3％ammonium sulfate solution.With an increase in the concentration of the leach solution,the same trend appeared.
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