Experimental Research On The Characteristics Of Moisture Infiltration Into Soils Under Non-sufficient Water Supply

In the paper, based on indoor tests of water infiltration into disturbed homogenized soils under non-sufficient water supply, the basic characteristics of infiltration and major factors influencing soil characteristics of infiltration were studied generally and systematically. A model used in predicting the time slice of soil hydroceling and infiltration model exponent through some soil physics parameters and water supply intensity was built up and method for predicting the infiltration procedure was put forward under non-sufficient water supply. The distinctions between sufficient water supply and non-sufficient water supply were analyzed and connection of them was established. Infiltration model parameters under non-sufficient water supply were deduced with infiltration model parameters under sufficient water supply.Soil water infiltration rate is a constant rate that equals to the value of water supply intensity under non-sufficient water supply before the time slice of soil hydroceling. After the time slice of soil hydroceling , Soil water infiltration characteristics are similar between non-sufficient water supply and sufficient water supply. There is no accumulated water on surface soil during the control stage of water supply intensity, so it is favorable to gas permeability. Through the infiltration amount under non-sufficient water supply is less than under sufficient water supply, with the soil infiltration, the curve of infiltration amount under sufficient water supply is the asymptote of the curves of infiltration amount of different water supplied intensity under non-sufficient water supply. The infiltration process corresponds with Kostiakov infiltration model after the time slice of soil hydroceling. The relation between soil wetting front and time is according to first-degree function before the time slice of soil hydroceling, the relation is according to power function after the time slice of soil hydroceling. The soil averaged moisture at the time slice of soil hydroceling is very close to that at the moment of experience finished, so the wetting front coincides with the piston model of Green-Ampt.The intensity of water supply and soil texture, specific gravity, moisture are the major factors which influence the infiltration capacities of soil under non-sufficient water supply. They have influence on the time slice of soil hydroceling vary clearly. The influence of each factor on soil water infiltration at each stage is different. Soil specific gravity have less influence on wetting front, and soil moisture have more influence on wetting front though the influence of them on hydraulic conductivity before the time slice of soil hydroceling. soil texture, specific gravity and soil moisture have influence on the rate of relative stability infiltration vary clearly, and water supplied intensity has little influence on it.It is feasible to predict the time slice of soil hydroceling by the routine physical parameters of soils with the help of linear regression model with multiple units. If water supply intensity,clay content (<0.002mm), silt content (0.002-0.02mm), specific gravity, moisture of soil are used to predict the time slice of soil hydroceling, the predicted results are satisfactory. By the same mean, the model can be used to predict the infiltration parameters of soil too. The processes of soil water infiltration modeled with the feature of infiltration under non-sufficient water supply are better than that modeled with the predicted parameter of the time slice of soil hydroceling.In the research, the infiltration characteristics are studied generally and systematically in order to guide agricultural non-sufficient irrigation, for example sprinkling. The experience is indoor test under changing the natural condition of soil and the infiltration is one-dimensional and vertical. There are a lot of work to do on the program for complexity of the condition of field and the research only stayed on a level of qualitative investigation.