Research On Soil Infiltration Mechanism And Infiltration Model Under Banded Sand Gully Model

This paper proposes a method to increase the infiltration of rainwater by arranging belt sand ditches.The effects of Sandy soil texture,original soil texture,distance,width and depth of sand trench on soil water movement characteristics were studied by using a combination of numerical simulation and experimental verification and using the HYDRUS-2D software,based on a large number of related literatures.Under the premise of analyzing the infiltration characteristics of gully under different influencing factors,the gully inflow was established in sections.The simplified prediction model of permeability provides a certain theoretical reference for the actual implementation of sand ditches.The main research results are as follows:（1）By simulating the infiltration process of sand ditches under different influencing factors,and analyzing its infiltration characteristics,it is concluded that laying sand ditches under the influence of different factors can increase the infiltration rate,and sand ditches have an increasing infiltration effect.（2）Under the influence of different factors,the sand ditch infiltration rate curve has an inflection point,and the sand ditch infiltration rate has a drop at the inflection point.This inflection point occurs because the sand filled in the sand trench is fully saturated.After the sand is fully saturated,the contribution of the sand to the infiltration rate of the sand trench decreases or even disappears.The infiltration enhancement effect after the inflection point is mainly due to the fact that the vertical wetting front corresponding to the sand trench and the vertical wetting front corresponding to the original soil are not on the same horizontal plane,and the water not only infiltrates vertically,but also migrates horizontally.（3）The sand gully infiltration rate before and after the inflection point is in accordance with the power function relationship,that is,i（t）=βt^-α.The value of the constant coefficientβ₁of infiltration rate before the inflection point can be understood as the infiltration rate per unit time of infiltration.Therefore,the depth of the sand trench has no effect onβ₁.The value ofβ₁has a power function relationship with the saturated hydraulic conductivity of the sand.The coefficientβ₁has a linear relationship with the original soil texture,sand trench distance,sand trench width and sand trench depth.The constant coefficientβ₂of the infiltration rate after the inflection point is related to the constant coefficientβ₁of the infiltration rate before the inflection point,the sand saturation time T₀,and the sand trench distance B.（4）By using single factor analysis,the relationship between each factor and saturation time of sand was studied.Through the research,it is found that the sand gully distance has no effect on the time when the sand reaches full saturation.A model for calculating the saturation time of sand using multi-element Regression analysis.The reliability of the model is verified by the design of Orthogonal test.（5）The relationship between infiltration rate and other factors was analyzed by single factor analysis,and the infiltration rate prediction model was established.The reliability of the model is verified by laboratory tests.The calculated values of the model are in good agreement with the measured values.