Solute Transport And Numerical Simulation In Saturated And Unsaturated Lateritic Soil

Based on increasingly serious environmental pollution situation in Guangxi, the essay mainly researches Guilin and Liuzhou lateritic soil. Combined with the existing physical test data of lateritic soil (liquid and plastic limits, particle distribution, mineral composition etc.), and then carryed out permeation experiments of soil samples, penetration test of saturated soil column and upward permeation test of unsaturated soil column. According to experiment results, conducted numerical simulation. Systematically analyzed laws of solute transport in lateritic soil. The main results were as follows:(1) Guilin and Liuzhou lateritic soil have different hydrodynamic properties. The former has more powerful water retention capacity, with higher water content under the same suction. Its permeability is smaller than the latter.(2) There are there parameters in dispersion-convection model:mean pore-velocity, dispersion coefficient, retardation factor. These parameters mainly affect the peak, initial time and change velocity of the breakthrough curve. There are another two parameters in two-region model:patitioning coefficient and mass transfer coefficient. With the decreasing of partitioning coefficient, two-region phenomenon is more obvious. With the increasing of mass transfer coefficient, it is less obvious. When mass transfer coefficient is up to a leveal,two-region model becomes dispersion -convection model.(3) Guilin and Liuzhou lateritic soil were formed by weathering eluvium talus. Using indoor shower experiment of soil column got the breakthrough curve, then using two models in CXTFIT to fit, it was found that two-region model is more suitable for two kinds of lateritic soil.(4) Comparing lateritic soil with normal soil, it was founded that there were not two-region phenomenon in sand, sandy loam, silty clay, heavy clay, clay loam, clay. That is related to particle distribution and mineral composition. The free oxides in lateritic soil is cement. Contrasting lateritic soil to other kinds of red soil, it was showed that the two-region phenomenon in lateritic soil was more obvious.(5) Complicated pore structure influenced upward permeation test in lateritic soil column. The water change was manifest, while the solute transport is sluggish. The migration amount of solute is quite small, the relative concentration was only to 30%. The fitting results of the unsaturated breakthrough curve by CXTFIT were not matched with the experiment results and the inversion parameters were abnormal. The simulation consequents of GEO-STUDIO on unsaturated lateritic soil were not ideal. But fit results can reflect the actual trend to a certain extent.