Characteristics of erosion evolution of unloaded loess slope in Yan'an under rainfall infiltration and surface runoff
It is of great significance to determine the regularity of rainfall erosion of unloading loess slope for geological disaster prevention and watershed ecological management.Taking the rainfall erosion disaster of the unloaded loess slope in Yan'an as the background,the effects of rainfall intensity and rainfall duration on the infiltration,runoff,soil loss and moisture content of loess slope were studied by using the self-developed rainfall infiltration and surface runoff test platform,and the erosion evolution law of loess slope under the action of rainfall was revealed.The results showed that:1)In the early stage of rainfall,the slope rainwater was mainly infiltration,and the infiltration amount was about 2～8 times of the surface runoff.With the increase of rainfall duration,the surface runoff showed an increasing trend and the rainwater infiltration showed a decreasing trend.The surface runoff was less than the infiltration under the condition of short duration heavy rainfall,while the condition of sustained heavy rainfall was the opposite.2)The erosion mud yield of slope surface was positively correlated with the rainfall intensity,and the soil loss quantity under the condition of continuous strong rainfall was about 10.81 times that of short duration heavy rainfall.3)The development process of moisture content of slope surface soil suc-cessively transformed from rapid growth,slow growth and then to steady state with rain fall frequency,and it was decreased with the decrease of rainfall intensity.Under the same rainfall intensity,the soil moisture content under continuous heavy rainfall increased by 9.62%compared with short duration heavy rainfall.The soil moisture content in the middle bottom of slope increased faster than that at the top of slope.4)The evolutionary process of slope ero-sion catastrophe under continuous heavy rainfall was rainwater infiltration,shallow surface soil wetting,intensive splash pits on the slope surface,surface runoff,shallow,thin and short erosion trench deep,wide and long erosion trench and shallow landslides,and the erosion damage range of slope surface was manifested as the gradual retreat from the slope foot to the top.
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