| Soil erosion on the slope surface of sandcap loess will cause serious effects such as water and soil erosion and soil degradation.Therefore,it is of great significance to study the slope erosion mechanism of sand-covered loess.In this paper,the sand-covered loess slope surface is taken as the research object,and the erosion of the sand-covered slope surface during rainfall is studied through indoor simulated rainfall test.Indoor simulated rainfall tests under different combinations of sand cover ratios under fixed slope and fixed rainfall intensity were used to observe the rainfall erosion process and slope erosion characteristics,such as runoff rate,sediment yield,sediment content and seepage rate,and to explore the influence mechanism of slope sediment cover on the change of erosion degree.The relationship between different sand cover ratios and changes of hydrodynamic parameters is explored by studying the variation regularity of hydrodynamic parameters under different sand cover ratios.Through the characteristics of sediment particles under different sediment cover ratios,the correlation between sediment cover ratios and sediment particle changes on slope surface under different rainfall times is analyzed.To explore the internal mechanism of slope erosion under different sand cover conditions,and to provide scientific basis for land management and water and soil conservation.The main conclusions are as follows:(1)Under different sand cover ratios,runoff,sediment yield,sediment content and seepage rate of slope surface show a trend of increasing first,then stabilizing or decreasing slightly with time.The larger the proportion of sediment cover,the higher the runoff rate,sediment yield and sediment concentration on the slope surface,but it also aggravates the erosion of water and soil erosion.Insufficient thickness of sand cover will reduce the ability to control water and soil loss.Under different sand cover ratios,the seepage rate gradually decreases,especially when the sand cover ratio is large,which aggravates the occurrence of slope runoff.(2)Under different sand cover ratios,the change trend of slope flow rate and runoff water depth with time is different.The larger the sand cover ratio,the higher the flow rate,the greater the fluctuation of runoff water depth.Reynolds number of slope surface is generally higher than that of bare slope under different sand cover ratios.With the increase of sand cover ratios,slope flow becomes turbulent and runoff resistance coefficient gradually decreases.Manning roughness can better describe the erosion of sand covered slope.The runoff power increases with the increase of the proportion of sediment cover on the slope,but the runoff on the fully covered slope is less than 75% of that on the sandy slope.Sand structure has a stronger degree of soil erosion than a single loess or windy sand terrain,and the unit runoff erosion power of incomplete sand cover is higher than that of a single loess or sand cover structure.These results indicate that the hydrodynamic characteristics of slope erosion have certain effects on the erosion process.(3)The fractal dimension of eroded sediment particles and the changes of sand and silt content can be divided into five stages,and have a quadratic function relationship with rainfall time.Under different sand cover ratios,the fractal dimension and the change law of sand and powder content were different,and the correlation was also different,and the correlation was the worst on the slope of the 25% sand cover ratio.The slope erosion rate with a small proportion of sand cover was positively correlated with the sand content and negatively correlated with the smaller particle content.The dominant factors affecting the erosion rate of loess slope were Fl,P and u.The 50% slope erosion rate was negatively correlated with sand and silt content,and positively correlated with smaller clay.The slope erosion rate with a large proportion of sand cover was not significantly correlated with the sediment particle content.The dominant factors affecting the erosion rate of semi-overlying sand slopes were Sl,P and u.These results provide insight into the evolution of sediment particle separation during slope erosion under different sand cover conditions. |
