The Methods Study On Calculating Soil Hydraulic Characteristic By Disc Infiltrometers

The influence of water content and energy capacity on soil's physical characteristics has exceeded any other elements, so soil moisture relationship has become leadership in the study of soil physics. A method was required to determination of unsaturated soil hydraulic characteristics quickly and accurately, especially in the field test. Disc infiltrometers just satisfied the requriment and developed steady, transient, and inverse methods to calculate soil hydraulic characteristics. Browning ideas from foreign research findings on disc infiltrometers, adopt both theory and experiment to analysis the feasibility of automated disc infiltrometers; the influence of contact material on the infiltration characteristics; the determination of the methods on calculating soil hydraulic characteristics; the use of Mini disc infiltrometers under different land use type; and. Major results are as follows:(1) The automechanism can be used to mensurate the infiltration process by using the disc infiltrometers, and can obtain accurate experimental findings through recording the infiltration process automatedly.(2) Through indoor test, the effectiveness of contact materials was analyzed. The numerical values of Cultivated loessial soils of cumulative infiltration, the infiltration rate, and the unsaturated conduvtivty would have slender increase with contac meaterials, but for the Tire soil, the situation was just on the opposite, the increase was evidently. So the contact materials should be used on Tire soil but not on the Cultivated loessial soils.(3) The method for calculating the soil's sorptivity for Dark loessial soils should be method 2, and for Cultivated loessial soils, Red clay soil, and Tire soil, both method 2 and method 3 were feasiable.(4) The cumulative infiltration for Cultivated loessial soils, Dark loessial soils, Red clay soil, and Tire soil would be accelerate obviously under the 5 cm diameters of the disc, but have no distict difference under 10 cm and 15cm diameters. Take the stability of the field experiment into account; the 15cm diameters should be adopted.(5) For Cultivated loessial soils and Red clay soil, the inverse solution model, the nonlinear regression model and the Bresler model were appropriate; for Tire soil and Dark loessial soils, the inverse solution model was suitable.(6) The infiltration rate and the conductivity would be increase under different land use, and the order of the land use was: alfalfa, Caragana Fabr., wild grass ground, returning farmland. But for the different sloping surface, the soil conductivity of the hill crest is greater than the bottom of the hill. So the site of the sloping surface and the land use will coactions on the structure of the soil.