Effects of muddy water infiltration on the hydraulic conductivity of soils by multiple factors

The infiltration of muddy water in soil has a complex change of upper boundary process. Among them, the hydraulic conductivity of soil has been one of the most important indicators for the infiltration characteristics of muddy water in the soil. In this study, a series of infiltration tests (9 orthogonal test treatments and 8 groups for the model validation) were performed on the muddy water in the saturated soil column. The hydraulic conductivity of the formed dense layer was also determined during the infiltration of muddy water. The dynamic model was then constructed for the hydraulic conductivity of the sand under multiple factors （sand content of muddy water, clay content, and infiltration time） using multiple regression. A verification test was made on the dynamic models of the hydraulic conductivity of the saturated soil columns in the muddy sandy and silt loam soil. It was assumed that the muddy water was infiltrated into the saturated soil column. The results showed that there were highly significant effects of the muddy water sand content, clay content, the gradation of sediment particles, and infiltration time on the hydraulic conductivity of the sand （ P<0.01）. The first factor was the infiltration time, followed by the sand content, and the last was the clay content. The coefficient of determination （R²）was 0.853 in the dynamic model for the hydraulic conductivity of sand, and the root mean square error was 0.004 cm/min, indicating the better-represented relationship between various factors and hydraulic conductivity. Meanwhile, the values of root mean square error was less than 0.01 cm/min, and the mean absolute value of relative error was less than 7%, indicating the highly reliable dynamic model of hydraulic conductivity. The R² values of the dynamic model were 0.912 and 0.930 for the sandy and silt loam, respectively, and the values of root mean square error were 2×10⁻³ and 5×10⁻⁵ cm/min, respectively. The values of root mean square error were less than 0.01 cm/min, and the mean absolute value of relative error was less than 17% in the model validation, indicating the excellent agreement between the calculated and measured. The finding can greatly contribute to the theoretical basis of the infiltration process of muddy water in the soil, together with the barrier mechanism of the dense layer.