Change Of The Infiltration Model And The Infiltration Parameters Fitting For Collapsible Loss

Water in nature is continuous and the water infiltration is an important part,water goes from through the soil to plant roots,spreads to the air and then enter the atmosphere.In the process,water is the basic of plants growing and living,and the only way of plant absorption is the surface water infiltrating,soil water and surface runoff are both made by the infiltration.Always,soil water is the key areas of agricultural water conservancy study,and plays an important role in planting,water-saving irrigation,the land desertification,etc.Especially in the loess area,the soil water infiltration changed because of swelling property of collapsible loess.In this paper,basing on reviewing the study and progress of water infiltration in foreign and domestic and designing the water infiltration test and rainfall infiltration test,the saturated soil moisture and saturated water conductivity can be analyzed,and the influence of infiltration is studied by the Philip model,Kostiakov model and Horton model.(1)By analysing the changing tendency of collapsible loess movement parameters,changing of soil physical parameters can be determined.According to the case of force-deformation: under the swelling force and self-weight stress,bulk density increases as the depth increase,soil water cumulative infiltration increases and the growth rate of it appears first quick back slow trend,runoff intensity increases,and the tests also provide powerful support to the soil water empirical formula for water infiltration.(2)Soil water empirical formula for water infiltration of expansive soil considering the volume change.By using the Philip model,Kostiakov model and Horton model,considering the physical meaning of parameters,change of the infiltration rate along with the infiltration depth as the main research object can be suitable for soil water characteristic curve.In the test,correlation of Horton model is higher than 0.9,with the consideration of other realistic factors,the Kostiakov model is more appropriate for the infiltration of saturated expansive soil,and Horton model can match the phase from the initial infiltration to the soil stable infiltration.So Horton model is an ideal model to simulate the soil water empirical formula considering influence made by the volume change.(3)Quantify the influence on infiltration made by the change of volume of expansive soil.According to the rainfall infiltration test,degree of influence made by the change of volume along with the infiltration depth can be gotten through analyzing the changing relation of the volume,geostatic stress,swelling force and the saturated hydraulic conductivity with depth.During the irrigation,the swelling force in each depth remains,the geostatic stress increases in each depth,and the saturated hydraulic conductivity decreases,and saturated water conductivity in each depth decreases,so the change in volume of collapsible loess has an influence on the infiltration.Changes and the influence on the infiltration of collapsible loess is given in this paper,quantified the porosity and the saturated hydraulic conductivity changes with depth,and concluded the suitable soil water empirical formula.It is meaningful for establishing and optimizing the model of infiltration and measure the saturated hydraulic conductivity.