| The waste dump slopes in open-pit mining areas in Inner Mongolia are widely distributed,undergoing severe soil and water loss,which has a serious impact on the regional ecological environment.Although all kinds of vegetation measures have been widely used in the process of slope management of the dump.Unreasonable vegetation configuration leads to the phenomenon of "green from a distance,more furrows from near",which seriously threatens the ecological environment of the mining area.Previous studies mainly focused on rill erosion on exposed slopes.However,the development processes and mechanisms of rills on dump slopes under vegetation configurations are not clear at present.Therefore,the rills of the dump slopes under different vegetation configurations in Minda Mining area of Inner Mongolia Autonomous Region were taken as the research object.Through field investigation and artificially simulated rainfall experiment,combined with redundancy analysis and Pearson correlation analysis,the existing main types of vegetation configuration were clarified.The temporal and spatial evolution of slope rill development under different vegetation configurations and the main factors affecting slope rill development were determined.The rill growth process of dump slope under different vegetation configurations was studied.The influence mechanisms of vegetation on the rill development of dump slope were expounded.The results and conclusions are as follows:(1)Elymus dahuricus and Artemisia ordosica are two typical artificial vegetation types in Dongsheng.Both can effectively restrict the rill development on dump slopes.Compared with the naturally restored slope,the rill erosion modulus of the two slopes decreased by 76.29%-90.77% and 53.25%-61.49%,respectively.The rill development of Elymus dahuricus slope was well controlled;the rill erosion modulus of artemisia orniflora slope and naturally restored slope decreased with the increase of the recovery year.The rill erosion modulus of Elymus dahuricus slope increases with the increase of recovery years.The control effect of Elymus dahuricus on rill development tended to weaken gradually.The interaction of different vegetation configurations and recovery years had significant effects on the average rill depth,rill density,rill dissection degree,and rill erosion modulus.However,their interaction has no significant effect on the average rill width.(2)Vegetation coverage is the most important factor affecting rill development of dump slope,and its variation explanation degree to rill development is as high as 34.99%.Soil particle composition also plays an important role in rill development.Clay content was second only to vegetation coverage(17.24%)in explaining rill development.With the increase of recovery years,the clay content of dump slopes tended to rise.The variation of the vegetation root system did not well explain the rill development of dump slopes.Root volume density explained the variation of rill development the most among all root indexes.The root volume density was negatively correlated with rill width,rill density,degree of rill dissection,and rill erosion modulus.The correlation between root mass density and rill development of dump slopes was not strong.(3)The time of runoff generation,falling-sill and rill occurrences in Elymus dahuricus slope lagged behind other types of dump slopes.The runoff generation time and rill occurrence time are in the order of bare slope < Artemisia orartemisia slope <artemisia mixed slope < Elymus dahuricus slope.The order of occurrence time of falling slope was exposed slope < mixed slope < Artemisia orartemisia slope <Elymus dahuricus slope.The average rill advance rate,average rill width and depth of Elymus dahuricus slope were lower than those of the mixed slope.The order of rill density and rill dissection degree was bare slope > Artemisia orartemisia slope >mixed slope > Elymus dahuricus slope.The variation trends of rill density and rill dissection degree of Artemisia orartemisia slope and the mixed slope were similar.However,the rill density and rill dissection degree of the mixed slope were lower than those of Artemisia orartemisia slope.In general,the rill dissection degree increased with the increase of rainfall times.Eventually,the rill dissection degree of the bare slope reached about 10%.However,the rill dissection degrees of Artemisia orartemisia slope and the mixed slope were stable in the range of 1～2%.The rill degree of Elymus dahuricus slope was stable within the range of <1%.The rill erosion modulus of each type of dump slope was in the order of bare slope > Artemisia orartemisia slope > mixed slope > Elymus dahuricus slope.The trends of rill erosion modulus of Artemisia orartemisia slope and the mixed slope were closer.However,the rill erosion modulus of mixed slope was always smaller than that of Artemisia orartemisia slope.(4)The runoff yield,runoff power,runoff shear force,sediment yield,and soil denudation rate corresponding to each vegetation configuration were in the order of bare slope > Artemisia orartemisia slope > mixed slope > Elymus dahuricus slope.These indexes were positively correlated with rill development.Vegetation configuration inhibits rill development by reducing the " driving force" of rill development.In addition,the soil clay content,infiltration rate,porosity,and organic matter of different vegetation configuration soils were in the order of bare slope >Artemisia orartemisia slope > mixed slope > Elymus dahuricus slope.These soil characteristics were negatively correlated with rill development.Vegetation roots increased the clay content of slope soil.Soil organic matter content and porosity were increased,soil infiltration rate was increased,and rill development was inhibited.Meanwhile,the shear strength of the corresponding vertical pressure was in the order of Elymus dahuricus slope > mixed slope > Artemisia orartemisia slope > bare slope.By winding the soil,vegetation roots can strengthen and anchor the soil layer of the dump slope and increase the shear strength of the soil.There was a significant negative correlation between soil friction angle and rill development.The internal friction angles of the dump slopes with different vegetation configurations were larger than the bare slopes.The internal friction angle of Elymus dahuricus slope is the highest.Each vegetation configuration can effectively increase the internal friction angle of soil.The shear strength of soil was improved,and rill development was inhibited.(5)The degrees of rill development under different vegetation configurations are in the order of Artemisia orartemisia slope > mixed slope > Elymus dahuricus slope.Elymus dahuricus could effectively control rill development.The control effect of Artemisia orartemisia on rill is weaker than that of Elymus dahuricus.The control effect of the mixde planting on rill development was weaker than that of Elymus dahuricus alone.Elymus dahuricus is an excellent vegetation type for early restoration of dump slope in Inner Mongolia mining area. |
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