The Preferential Passage And The Law Of Preferential Infiltration Of Loess Slope

Loess slopes have a large number of preferential passages that are in favor of rainfall or irrigation water quickly infiltrate into slopes,the loess geological hazards caused by this problem cannot be ignored.This study through dividing the preferential passages of loess slopes,in-situ monitoring tests and numerical simulation analysis of rainfall infiltration,to carry out the relevant research work of the law of preferential infiltration and its infiltration mechanism.The main achievements are:(1)Through literature researches and field investigations,the preferential passages in the loess region was divided into Class I preferential passages with primary macropores and vertical tubular passages,and Class II preferential passages dominated by micro-joint fractures,macropores,and small caverns,class III preferential passages include large joints,fractures and sinkholes;(2)Summarizing the spatial-temporal development characteristics of the preferential passages,proposing three stages of the development and evolution of the preferential passages: budding period,forming period and development period;and the distribution of the preferential passages in the slope area is summarized as an undeveloped preferential passages,and the comparative advantage zone of the preferential passagesand the development of the preferential passages,this laid the foundation for the subsequent study on the infiltration mechanism;(3)Combined with the evolutionary process of the preferential passages,the law of moisture migration in the unsaturated zone can be generalized into three types of infiltration modes: uniform infiltration,preferential infiltration and pour into infiltration,and take these modes as a prototype,proposing the schematic diagram of the concept of different infiltration modes.,and through the field test and Hydrus2 D numerical simulation revealed the infiltration laws under different preferential infiltration modes;(4)The in-situ monitoring tests under different infiltration modes were conducted in Yan'an and Jingyang by methods such as moisture content monitoring,high-density electricity monitoring and geological radar detection.In the homogeneous infiltration model,rainfall infiltration has hysteresis,rainfall mainly affects the water content of surface soil,and the monitoring depth of rainfall infiltration is limited;however,the results of preferential infiltration and pour into infiltration high-density electrical test have been verified.The preferential passages is a high-speed channel where rainfall or irrigation water and groundwater are hydraulically linked,and it is visualized as a low-resistivity distribution near the preferential passages;(5)The numerical simulation analysis of seepage field changes and slope stability caused by preferential infiltration on loess slopes shows that the slope seepage fields of cracks(falling water holes)at different distances and depths show the development of wet fronts and cracks(sinking holes).The morphology remains the same,the seepage field changes significantly,and the dominant infiltration on slopes has a greater impact on slope stability.