Study On Soil Water Retention Curve And Fractal Model

The hydraulic properties of unsaturated soil describe the soil’s ability of saving and releasing water, which play an important role in the research of the water’s transport and the pollutant diffusion. The quantitative research on the soil struc-tural and hydraulic characteristics can provide theoretical support for simulating and discovering the rule of the water and nutrient movement.This paper mainly studies the soil hydraulic models. The main work is:1. Based on the different sets of the unsaturated soil database, we use the dif-ferential evolution algorithm to do the regression statistics, predict the soil retention curve, obtain the parameter estimation in different soil moisture and environment, and the effect of soil texture and sampling on parameter fitting precision.2. The hydraulic conductivity of unsaturated soil is an important function for using the mathematical model to calculate the water movement. Based on Mualem-van Genuchten model, we use the independent parameters or relation between pa-rameters and hence build three different calculation method of the hydraulic con-ductivity. We judge the effect of the freedom degree on the hydraulic conductivity by comparing its value from the calculation and experiment.3. The soil is a non-uniform and porous complex system and irregular geomet-rical structure with particles with different form and size. Therefore, fractal theory is applied to the soil science as useful tool to study irregular objects. According to the size distribution of soil particle in the unsaturated soil database the and the water retention curve, we apply the differential evolution algorithm and fractal models to calculate the volume fractal dimension of the soil and to do the statistical research on the relationship between fractal dimension and soil water saturation, entry pressure, and soil texture, ete.