Characteristics Of Soil Water Infiltration Of Water Repellent Sandy Soil

Water infiltration plays an important role in the cycle of the water in nature.. The presence of water repellent soil has a serious impact on the soil water infiltration, the absorption of rainfall and irrigation water, and also has an indirectly impact on the environment for the growth of crops. Researches on water repellent soil is relatively mature abroad, but the domestic research is relatively less in China.This paper studied the water repellent sand moisture characteristic curves of different density and different degrees, analyzed the variation of moisture characteristics of different sand density; simulation of soil moisture and desorption process and analysis the changes of water-repellent time follow the soil water content; through indoor soil box infiltration testing, analysis the infiltration characteristic of different initial moisture content of water-repellent sand. The conclusions are stated as follows:(1) The changes of water drop penetrated time with soil water content in sorption and desorption process of sand soil.Three different levels of water-repellent sandy soil were formulated with the sand sample and surface active water-repellent material(octadecyl primary amine), then simulate sandy soil moisture and desorption process, measure and analysis the relationship between water drop penetration time versus soil water content in the two process.WDPT(water drop penetrated time),peak water content and the "transition zone" is larger in soil moisture process than in the desorption process; peak moisture content remained the same in different degrees of water-repellent of sand soil in the sorption and desorption processes; "transition zone" increase both in the sorption and desorption process.(2) Soil water characteristics of differernt density and different degrees of water repellencySoil moisture characteristic curve were measured with Japanese-style centrifuge, the test set six different grades of water-repellent, four different density levels, a total of 24 processing, analyze and discuss soil moisture characteristics with different density and the same degreen of water-repellent and also the opposite condition. Soil water suction decreases with the increase of the bulk density and water-repellent degree while the soil moisture content is unchanged.(3) Affections of different initial moisture content on water-repellent sand infiltration characteristicsFive different initial moisture content of water-repellent sand were prepared, and the soil infiltration experiment were conducted with box in room,analyze the changes of wetting fronts with time, the changes of wetted area over time, the changes of the distribution of soil moisture and also the characteristics of soil infiltration rate in conditions of different initial moisture content.Wetting front advancing slowly, followed by a turning point, after turning the infiltration rate is very quick, finally stabilized; the changes of infiltration area generally exhibits a linear relationship; the distribution of water-repellent sand contours is not smooth and rule; the overall trend of infiltration rate is gradually reduced, and finally stabilized, the initial infiltration rate of 1%, 1.5%, 2%, 3% is significantly less than 5%. The rule of 5% of the test results consistent with the hydrophilic soil.