| A large amount of abandoned soil and slag produced by production and construction projects is the main source of new soil erosion.Planting vegetation and engineering measures are important ways to control soil erosion.Because the control measures are affected by many factors,the slope erosion reduction effects are different under different conditions,and there is not enough research and accumulation on the spatial layout of soil and water conservation measures under the condition of accumulation,so it is particularly important to study the slope erosion law of accumulation under the condition of composite measures.This article takes the high and steep slope of engineering accumulation as the research object,using constant current scour experiment,the design measures for 6 kinds of slope(bare slope,plant hedge,level trench,and fish scale pit,hedgerow+level trench,hedgerow+fish scale pit),Three water discharge rates(8,12 and 16 L/min)were used to investigate the slope erosion process,flow and sediment reduction benefits,runoff and sediment regulation,hydrodynamic characteristics and erosion sediment particle characteristics of engineering deposits under different measures.The preliminary conclusions are as follows:(1)The influence of different measures on the hydrodynamic characteristics of slope runoff and the relationship between hydrodynamic parameters and sediment yield are revealed.Under experimental conditions,the flow velocity,Reynolds number,runoff shear force and runoff power of composite measures are less than those of single measure and bare slope,and are reduced by 25.51%～44.03%,47.67%～63.81%,25.79%～52.10%and 33.09%～66.37%,respectively.Froude number showed as follows:bare slope>hedgerows>fish scale pit>level ditch,while the resistance coefficient of level ditch increased by-7.25%～114.65%compared with bare slope.The sediment yield on slope is positively correlated with velocity,Reynolds number,runoff shear force,runoff power and Froude number(P<0.01),and negatively correlated with drag coefficient(P<0.01).The flow velocity and runoff power had great influence on sediment yield,and there was a very significant power function relationship between sediment yield and them(R~2=0.135～0.555,P<0.01).Froude number had the weakest influence on sediment yield.(2)The effects of different measures on the relationship between runoff and sediment yield on slope surface of accumulation body were investigated.Under the experimental conditions,the runoff yield and sediment yield of different water conservation measures were as follows:bare slope>hedgerow>fish-scale pit>level ditch>hedgerow+fish-scale pit>hedgerow+level ditch,and the average runoff yield of each measure decreased by 16.65%,16.98%,24.69%,26.82%and 34.69%compared with bare slope,respectively.Compared with bare slope,the average sediment yield of all measures decreased by 38.03%,45.22%,51.41%,65.51%and72.79%,respectively.There is a very significant power function relationship between the cumulative discharge and the cumulative sediment yield(R~2=0.945～1.000,P<0.01),and the cumulative sediment yield growth rate of compound measures is smaller than that of single measures.(3)The effects and timeliness of sediment reduction by different measures are quantified.Under the experimental conditions,all the measures have the effect of water storage and sediment reduction.The combined water conservation measures have the advantages of 28.17%～37.17%and 14.37%～24.94%respectively,and the sediment reduction benefits are 38.83%～77.45%and 14.11%～57.80%,respectively.The accumulative sediment reduction is 13.80～16.62 kg and 4.85～15.30 kg,respectively.The amount of runoff reduction and sediment control is greater than the amount of sediment control based on the relationship between water and sediment,and the reduction of runoff is the dominant factor of slope erosion and sediment control by water conservation measures.The efficiency coefficient of sediment regulation under hedgerow+level ditch is higher than other measures,and the two measures can better regulate runoff and sediment.(4)The effects of different measures on the distribution and sorting characteristics of erosion sediment particles were clarified.Under the experimental conditions,the erosion sediment particles are mainly composed of fine silt and coarse silt,followed by sand,and clay particles account for the least,with the contents of each particle being 33.68%～44.02%,25.5%～32.66%,18.55%～27.32%,7.06%～10.73%,respectively.The enrichment effect of fine silt particles is the strongest,and its content and enrichment rate decrease with the increase of discharge,while the content and enrichment rate of sand particles are the most difficult to be transported,and increase with the increase of discharge.The content of fine powder and its enrichment rate of composite measure are higher than that of single measure and bare slope,while the content of sand and its enrichment rate are lower than that of single measure and bare slope.Coarse particles migrated basically as single particles,while clay particles,fine particles and sand particles migrated as aggregates.The correlation between the volume fraction of clay particles and the volume fractal dimension is the best,which is extremely significant linear positive correlation(R~2=0.855,P<0.01). |
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