Research On Hydraulic Properties Of L₁-S₇ Soil Layers In Loess Section Of Changwu In Shaanxi Province

Many researches have been conducted on loess-paleosols in Loess Plateau of China,and some research results have been made in climate change of Loess Plateau and intensity of pedogenesis. However,there are little research about enriching rules and conditions of loess groundwater at home and abroad so far.We researched the enriching conditions of loess groundwater in Loess Plateau from hydrological characteristics and intensity of pedogenesis,which is important in science and reality to reveal the enriching rules of loess groundwater and rationally use of water resources and ecological construction in Loess Plateau.Based on the detailed investigation,we chose an intact section near Beishui ditch in 2km east of Changwu,made samples collection and infiltration experiment on the section bed,and made porosity determination,granularity determination, magnetic susceptibility determination and content of CaCO₃ determination.According to the experiments' results,we come to the following conclusions:1.The average stable infiltration rate of loess layers in L₁-S₇ of section is larger than the paleosol layers.The stable infiltration rate of the fifth and sixth loess layers is much larger and the infiltration of the forth paleosols layer.The stable infiltration rate of the forth paleosols is larger than the paleosol of other layers,which is abnormal.The stable infiltration rate of the loess in the fifth layer is the largest and the loess in the sixth layer is the next-largest.2.In the process of infiltration,the infiltration rate of loess is faster than the paleosol layer,but the time to reach the stable infiltration rate is longer than the paleosol layer.In about 20 minutes of the infiltration of loess layer,the infiltration rate is the biggest,which is about 2mm/min,and the slope of infiltration curve is big.After about 20 minutes of infiltration process,the infiltration curve is gentle but the infiltration rate is still large,which is about 1mm/min.After about 60～80 minutes of the infiltration process,the infiltration curve nearly becomes a straight line and the infiltration rate is stable.The infiltration of paleosol layer shows the similar character.In the first 10 minutes the infiltration rate is the largest,which is about 1.5mm/min.But it is smaller than the loess layer.After about 20 minutes of the infiltration process,the infiltration curve is gentle but the infiltration rate is still large,which is about 1mm/min.After about 50～60 minutes of the infiltration process,the infiltration curve nearly becomes a straight line and the infiltration rate is stable.The fifth paleosol layer of the section consists of several layers and needs a longer time to reach the stable infiltration rate than other paleosol layers.3.In the L₁-S₇ of section,the magnetic susceptibility of the loess is lower than the paleosol layers,the granularity of the loess layers is thicker than the paleosol layers and the content of CaCO₃ of the loess is higher than the paleosol layers.The difference of the magnetic susceptibility and CaCO₃ content between loess layers and paleosol layers reflects the climate difference and the pedogenesis.In the colder and dryer climate conditions,pedogenesis is weaker.Bnd in wetter climate conditions,pcdogenic action is stronger.By contrasting the hereinbefore experimental guidelines,we conclude that the pedogenesis of paleosol in the first layer(S₅¹) and the forth layer is the strongest,and the pedogenesis of loess in the fifth and sixth layer is the weakest.4.In the L₁-S₇ of section,the porosity of loess layer is generally larger than the paleosol layer. Loess layer has a weaker pedogenesis,which makes the granularity of loess layer is thicker,the porosity larger,the hydrated space better and the infiltration stronger.The granularity of paleosol layer is thinner and the porosity is smaller,the hydrated space is worse and the infiltration is weaker. The difference makes loess layers easy to form the hydrated layer.And the paleosol layers easy to form relatively water-resisting layer.5.In the section,the fourth paleosol layer has a stronger pedogenesis,which makes the granularity of paleosol layer thicker,the porosity thinner,the ply of forth paleosol thin and the lengthways cranny grownthful.That makes the infiltration strong.So the forth paleosol layer is hard to form the water-resisting layer.6.The hydrated space of loess layers grows well,and the high infiltration rate is decided by the cold and dry climate in ice age.The hydrated space of paleosol layers grows badly,and the low infiltration rate is decided by the hot and wetness climate in interglacial period.