Experimental Study On The Law Of Water Infiltration Into Freeze-Thaw Soils

In this paper, based on the tracing field infiltration tests into frozen and unfrozen soils with three species of soil texture and eight species of soil structure in seasonal frozen soil regions during three overwinters, the basic infiltration characteristics, reduction infiltration mechanism and major factors influencing soil infiltration characteristics are studied all-sidedly and systematically. To master frozen soil infiltration characteristics and supply scientific directions for winter irrigation.Frozen soils are of evident reduction infiltration characteristics and the infiltration capacities of frozen soils change clearly within a year and a day. The infiltration capacities of frozen soils are clearly less than that of the unfrozen soil under the same conditions. The varying procedure of the infiltration capacities of frozen soils within a year is in keeping with second-degree polynomial functions and the varying procedure of the infiltration capacities of frozen soils within a day corresponds with third-degree polynomial functions. The irrigation process of frozen soils is analogous with unfrozen soils and corresponds with K o c T R K o B infiltration model. The fundamental reason why the infiltration capacities of frozen soils reduce is the reduction of hydraulic conductivity of frozen soils and the fundamental reason why the hydraulic conductivity of frozen soils reduce is the phase change of liquid state moisture in soils. The phase change of soil moisture and inflation of the frozen moisture cause the reduction of hydraulic conductivity by reducing the area of flow section and the aperture of soil pore space, increasing the capillary resisting force to soil moisture, and decreasing the water potential gradient because of the increasing of movement distances of soil water.Soil texture, moisture, bulk specific gravity, ground temperature and irrigation water temperature are the major factors which influence the infiltration capacities of frozen soils. Ground water table influences theinfiltration capacities of frozen soils by its influence on ground soil moisture. Because ground temperature is the deterministic factor which result in the phase change of liquid state moisture in soils and determines the degree of the phase change of liquid state moisture, it is the one of important influencing factors on infiltration capacities of frozen soils. When the ground temperature at 5 cm depth below surface reduces to -4.0C, infiltration capacities of frozen soils come to the minimum. It will have less influence on infiltration capacities when the temperature drops further.In the research, the infiltration characteristics of frozen soils and the characteristics of winter irrigation flow are studied all-sidedly and systematically in order to guide agricultural winter irrigation, but there a lot of work to do on the program for the complexity of the researched problem and the finiteness of research method and means in many aspects the problem has not yet been resolved or the research only stays on a level of qualitative investigation. Due to writer's poor knowledge , there must be some faults and shortcomings in the paper.