| In recent years,with the rapid development of national economy,large-scale construction projects such as transportation,water conservancy and electric power have been increasing,and construction disturbance of production and construction projects has become the main cause of man-made soil and water loss.In production and construction projects,the engineering accumulation bodies formed by dumping and piling are mostly of"platform-steep slope"structure.Under the condition of short duration and heavy rainfall,the water from the upper part of the platform confluence will cause severe soil erosion.At present,most of the research methods for engineering accumulation are based on outdoor simulated runoff and clear water scour test.However,in the actual slope scour process,the incoming water from above has a certain amount of sand content,which is not consistent with the actual situation.Therefore,it is particularly necessary to carry out the research on the scour test of muddy water.In this study,the field simulated runoff erosion test under different conditions of muddy water scours(The concentration of sediment is 0%,4%,8%)was used to reveal the rule of erosion,runoff and sediment;the hydrodynamic process;and the sorting mechanism of erosion sediment particles of the loess slope engineering accumulation.In order to improve the theory of accumulation slope erosion mechanism,contribute to establishing the slope erosion prediction model,provide a strong data reference and theoretical basis for rationally allocating soil and water conservation system.The main conclusions of this paper are as follows:(1)The runoff rate and sediment rate and their fluctuation were 0%>4%>8%(3 types of muddy water scour).Under the condition of each muddy water,the runoff rate and sediment rate and its fluctuation on the slope increased with the increase of water flow and slope.The greater current sediment content of muddy water,the smaller cumulative runoff,and cumulative sediment yield(0%>4%>8%);The greater flow discharge and the slope gradient,the greater cumulative runoff and cumulative sediment.There was also a very significant linear relationship between cumulative runoff and cumulative sediment yield(R~2>0.99,P<0.01).(2)Under 3 types of muddy water,Re,v,?and?all showed 0%>4%>8%.The influence of sediment concentration on Fr was not significant.In our experiment,the Froude number is greater than 1.The runoff flow regime was rapids,and the dominant force was the inertia force.The more sediment content was closer to 0,the more complex was the change of flow pattern.Under different muddy water scour conditions,the critical conditions for the transition from laminar flow to transition flow were that the discharge flow was greater than 12 L/min,and the slope was greater than 28°.(3)By analyzing the correlation between each hydrodynamic parameter and runoff yield and sediment yield on the slope,it can be obtained that:Re and?were the two parameters with the highest correlation with runoff yield on the slope.The order of correlation between each hydrodynamic parameter and runoff yield under the scour of muddy water flow was as follows:Re>?>?>h>v>Fr.According to the correlation with sediment yield,the order was as follows:?>Re>?>v>h>Fr.According to the order of the overall influence on the runoff and sediment rates of slope,it can be sorted as follows:?>Re>?>v>h>Fr.?was the most important factor affecting runoff and sediment rates on slope,followed by Re,Fr had the lowest correlation with runoff and sediment rates on slope.(4)Under the scour of muddy water,the clay particles only account for a very small proportion,and the silt and sand particles were dominant in the erosion of particles.The proportion of clay particles and fine powder particles before the dispersion of eroded sediment decreases with the variation of flow discharge and the slope gradient but increased slightly with sediment content of muddy water.The change of sediment particles after the dispersion treatment was generally consistent with the value before the dispersion.However,the rule between the sediment content of the muddy water tends to be stable,which showed that the larger the sediment content is,the more fine sediment(clay and fine powder particles)transported by erosion.There was a significant linear relationship between the content of fine particles(clay and fine powder particles)and the fractal dimension before and after dispersion(R~2>0.81,P<0.01),and the goodness of fit before dispersion was higher than that after dispersion.When the fine sediment was transported,the worse the soil texture was,the more difficult it was for vegetation restoration in the later stage.The difficulty of vegetation restoration on the slopes scoured by different muddy water is 0%<4%<8%.(5)The enrichment rates of fine particles in the sediment particles eroded increased with the increase of sediment content of muddy water on the accumulation slope(0%<4%<8%),and decreased with the increase of slope position extended(upper>middle>lower).According to the slope upper,middle and lower parts,the enrichment rates of fine particles decreases with the extent of slope position and the coarse particles increase.It indicated that the upper slope surface soil texture was the worst when erosion occurs,and the further down the slope,the better the soil texture was.The accumulation rates of sediment particles in the upper part of the slope had a strong regularity with the change on slope and water flow,the middle part of the slope had a strong regularity with the change on water flow,and the lower part of the slope with the sediment content of muddy water had a good regularity,which could be used to predict the sediment particles in each part of the slope.The agglomeration rates of fine particles of sediment eroded with the increase of sediment content of muddy water on the accumulation slope(0%>4%>8%),and decreased with the extent of slope position(upper>middle>lower).The agglomeration rates of erosion sediment varied regularly with the flow on the whole slope,the relationship between the lower slope and the slope gradient was significant,and the rule between each slope position and the sediment content of muddy water was not significant. |
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