Study On The Erosion Characteristics Of Red Soil Slope Under Water Saturation Condition And Seepage Condition

The characteristics of slope erosion in red soil regions in Southern China under different near-surface hydrological conditions were explained to provide important scientific basis for the soil erosion prevention and control in red soil regions and the continuous utilization of red soil resources.For the two kinds of near-surface hydrological conditions of slope in red soil regions in Southern China,this paper,by the method of indoor artificial simulation of rainfall,studied the characteristics of red soil slope erosion under saturation(SA)condition and seepage(SP)condition and explored the process of runoff and sediment generation,the particle distribution characteristics of the sediment generated and correlation between changes in hydrodynamic characteristics and sediment generation due to hydrodynamic erosion on red soil slopes under SA and SP conditions.(1)This paper studied the changes in the characteristics of red soil slope erosion under SA and SP conditions.Generally,the variations of red soil slope erosion are in the following order: SP20>SP10>SA.When transiting from SA condition to SP condition,the total slope runoff increases by 6.72%~50.08%,the total amount of erosion by 54.44%~393.32% and the sediment concentration by 28.30%~ 244.80%;in terms of the erosion process,at the beginning of rainfall,the sediment concentration under SP condition is significantly higher than that under SA condition,but the difference narrows with the extension of rainfall duration;SP makes contribution to slope runoff and sediment generation and the contribution to sediment generation is greater than that to runoff generation.(2)This paper studied the distribution characteristics of sediment particles on red soil slopes.With regard to particle size,the indexes(D10,D50 and D90)are in the order of SP20>SP10>SA;when transiting from SA condition to SP condition,D10,D50 and D90 increase by 15.71%~114.39%,16.19%~413.43% and 1.05% ~ 47.24% respectively;in terms of particle composition,slope sediment particles have similar composition with original soil particles and are mainly composed of powder particles(60~80%),but sediment particles are coarser,which is presented as lower clay content and higher sand particle content.When transiting from SA condition to SP condition,the clay content and powder particle content in sediment particles decreases by 2.86%~48.37% and 5.18%~35.59% respectively,but sand particle content increases by 11.09%~84.56%;in terms of particle concentration,the particles concentrated under the two conditions mainly are sand particles,the concentration rate of which increases by 12.82%~102.23% when transiting from SA condition to SP condition;with regard to the distribution of sediment particles,there is significant difference in particle size,particle composition and concentration rate at the beginning of rainfall under near-surface hydrological conditions,but such difference narrows with the extension of rainfall duration.(3)This paper studied the changes in the hydraulics parameters of red soil slopes under SA and SP conditions.In terms of hydrodynamic parameters,when transiting from SA condition to SP condition,the average slope velocity increases by 23.43%~60.01%,runoff depth by 6.25%~24.69%,Reynolds number by 12.38%~158.39%,Froude number by 9.09%~19.05%,but drag coefficient decreases by 6.40%~18.33%;with regard to hydrodynamic parameters,the runoff shear force and the stream power increases by 36.16%~53.13% and 75.00%~138.46% respectively under SP condition.(4)This paper studied the correlation between hydrodynamic erosion of red soil slope and sediment generation under SA and SP conditions.In terms of sediment particles,D50 is significantly correlated to velocity,runoff shear force and stream power(the correlation coefficient is 0.581,0.734 and 0.805 respectively),and D50 is in quadratic function relation with runoff shear force and stream power;with regard to soil erosion index,it is greatly influenced by velocity,runoff shear force and stream power(the correlation coefficient is 0.666,0.915 and 0.865 respectively),and soil erosion index is in a linear mean relation with runoff shear force and stream power;when transiting from SA condition to SP condition,the correlation and fitting degree of hydrodynamic parameters with slope erosion and sediment particles are higher,indicating that the runoff has greater effects on slope erosion under SP condition.