Infiltration calculation of soil with sand in layer

An infiltration calculation solution for the soil with sand inter layer, including the time when nonlinear infiltration transmits into the steady infiltration and the steady infiltration rate, was developed based on the Lab experimental data and exiting infiltration equations. According to the Kostiakov infiltration equation and the water storage amount of the upper layer at saturation, the water volume balance equation was established, and the time when nonlinear infiltration transmits into the steady infiltration was obtained from the water volume balance equation. The ratio of the steady infiltration rate with the infiltration rate of the uniform soil corresponding to the time when nonlinear infiltration transmits into the steady infiltration were calculated, and the functional relation of the ratio with the depth of the upper layer and the medium particle size of the sand was founded by the correlation analysis method. Hence, the steady infiltration rate may be calculated based on the depth of the upper layer, the medium particle size of the sand and the infiltration rate of the uniform soil corresponding to the time. The method was evaluated through experimental data, and the relative error was less than 5%. This method requires accurately measure the particle size of the sand, the depth of the upper layer and the infiltration rate of the uniform soil corresponding to the time, therefore the method need to be further improved and evaluated.