Mechanism Of Soil Structure Damage By Raindrops Splashing On Karst Slope Farmland

Slope farmland in the southwest karst region is one of the major soil erosion areas in China,and hydraulic erosion is the main mode of soil erosion occurring in the region.As the initial stage of hydraulic erosion,raindrop splash can disperse and migrate the surface soil aggregates,enhance the erosion of surface runoff,intensify soil erosion and seriously harm the ecological environment safety of the area.However,currently,the study of the splash erosion law in the initial stage of soil and water loss in karst area is relatively weak and how to damage the soil structure.Therefore,typical karst lime soil was studied,self-designed raindrop generator and 5raindrop diameters were used to carry out experiments on lime soil under different rainfall conditions,aiming at exploring the characteristics and laws of soil splash erosion.The research results can provide scientific theoretical basis for soil erosion mechanism and soil erosion in karst areas.The main results are as follows:(1)For the same slope,the soil pore area of five raindrop diameters decreased with the increase of rainfall duration;for the same rainfall duration and raindrop diameter,the soil pore area increased with the increase of slope.Under the same slope and rainfall duration,there was a linear function relationship between the amount of splash detachment and raindrop diameter,and total splash erosion mass of five raindrop diameters was mainly distributed at splash distance 0-5cm.(2)The amount of splash decreases with the increase of the distance;When the distance of splash is the same,the amount of splash increases linearly with the increase of the diameter of the raindrop.When the slope is the same,the total splash erosion of the diameter of 5 raindrops is exponential function with rainfall duration;When rainfall duration is the same,the splash erosion amount under different raindrop diameter increases with the increase of slope,which is power function.(3)Under the same rainfall duration and different slope conditions,the > 5mm did not appear;with the increase of slope and raindrop diameter,the >2-5mm and >1-2mm are increasing;the splashed aggregates were mainly distributed in>0.5-0.25 mm and < 0.25 mm fragments;For <0.25 mm size fraction,the mass percentage presented a fluctuated improving trend with splash distance increasing.(4)The slope is 0 °,the mass percentage of >1-2mm,>0.5-1mm,>0.5-0.25 mm and<0.25 mm increased first and then decreased,decreased first and then increased,decreased first and then increased,increased first and then decreased with the increase of raindrop diameter at the splash distance 0-5cm and 5-10cm;and its increased,increased first and then increased,increased first and then decreased at 10-15 cm,15-20 cm and 20-25 cm,respectively.The slope is 5°,except for>2-5mm,the mass percentage of the splashed aggregates increased,decreased first and then increased,decreased first and then increased,and increased first and then decreased with the increase of the raindrop diameter.The slope is 10 °,the mass percentage of each particle size fraction of 0-25 cm splash distance increases,increased,fluctuated,fluctuated and fluctuated with the increase of raindrop diameter.(5)The results show that the MWD of the five raindrop diameters decreased with the increase of the splash distance,and the relationship between the mass diameter and the raindrop diameter is a second power function;For the same slope and raindrop diameter,the D increased with the increase of splash distance,and the it first increased and then decreased with the increase of raindrop diameter;the ER increased with the decrease of aggregate size.(6)Raindrop diameter is the largest factor affecting the amount of splash detachment,MWD,D and ER,while splash distance is the largest factor affecting aggregate size distribution.