Study On Numerical Simulation Of Sand-Layered Soil Water Movement Under Film Hole Irrigation

The paper is based on the soil water infiltration theory of film hole irrigation and Sand-Layered soil water movement,studying the rule of sand-layered soil water infiltration under the film hole irrigation.It used the way of the laboratory test and numerical simulation and was solved by the SWMS-2D soft-ware.Using the model analyzed the characteristics of sand-layered soil water infiltration in the different influence factors and contrasted the soil water infiltration rule of the uniform soil and sand-layered soil.(1)The sand-layered soil water infiltration mathematical model which was based on the equation of Richard was established,and the SWMS-2D soft-ware was used to solve the model.The mean absolute error(MAE),root mean square error(RMSE),percent bias(PBIAS)and Nash-Sutcliffe efficiency(NSE)were used to evaluate the simulation data and measured data of cumulative infiltration,soil wetting front and soil moisture content.The statistical results are that MAE and RMSE is close to 0,PBIAS is less than 10%(-6.36%~-0.81%),and NSE is close to 1(>0.97).The result shows that the measured data and simulation value have good consistency.The model can accurately reflect sand-layered soil water infiltration under film hole irrigation,and SWMS-2D can be used as a research tool to simulate and analyze the infiltration characteristics of sand-layered soil water movement under the condition of film hole irrigation.(2)The model were used to study sand-layered soil water infiltration in the different influence factors.The film hole diameter,sand-layered soil texture and water head have an effect on cumulative infiltration,soil wetting front and soil moisture content.The result shows that the film hole diameter,the sand-layered soil texture and water head have a greater effect on soil moisture content,the film hole diameter and water head have a greater effect on cumulative infiltration,the sand-layered soil texture has little effect on cumulative infiltration,The film hole diameter,sand-layered soil texture and water head have different effects on soil wetting front.(3)By the comparison of soil water infiltration between the uniform soil and sand-layered soil,The result shows that the sand-layered has little effect on cumulative infiltration,they have different shape of soil moisture(the uniform soil likes hemisphere,sand-layered soil likes square),the sand-layered has an effect on soil wetting front and a distinct effect on soil wetting front in vertical direction.