| In order to realize the prevention and control of soil erosion on the steep slope of the production and construction project,and the optimal layout of vegetation,these were based on the example of the steep slope of the engineering accumulation at Yangling Soil and Water Conservation Field Science Experiment Station on Institute of soil and water conservation Chinese Academy of Sciences.Using the combination of field runoff scouring test and indoor erosive sediment particle size analysis,5 planting patterns(slope of bare,upper,lower,middle and strip)and 6 flows were designed(3 constant flows : 10,20,30 L/min,3 variable flows : 10-20-30,20-30-10,30-20-10 L/min),explored the characteristics of runoff and sediment,the benefits of reducing runoff and sediment,and the characteristics of eroded sediment particles under different vegetation patterns on the slope of loess accumulation.The preliminary results were as follows:(1)Under the test conditions,the runoff rate and sediment rate fluctuated with the prolonged of the scouring time.Among the five patterns,the runoff rate of the bare slope was the largest,the lower pattern was larger,the middle pattern was third,the upper pattern was smaller,and the strip pattern was the smallest.The latter four runoff rates account for the bare slope runoff rate were 73.20%,70.68%,57.47% and 47.91%.Among the five patterns,the sediment rate of the bare slope was the largest,the lower pattern was larger,the middle pattern was third,the upper pattern was smaller,and the strip pattern was the smallest.The latter four sediment rates account for the bare slope sediment rate were 61.98%,48.06%,44.49% and 33.64%.(2)Under the test conditions,among the five patterns,the cumulative flow of the bare slope was the largest,the lower pattern was larger,the middle pattern was third,the upper pattern was smaller,and the strip pattern was the smallest.The latter four cumulative flow account for the bare slope cumulative flow were 72.87%,70.67%,57.75% and 47.89%.Among the five patterns,the cumulative sediment of the bare slope was the largest,the lower pattern was larger,the middle pattern was third,the upper pattern was smaller,and the strip pattern was the smallest.The latter four cumulative sediment account for the bare slope cumulative sediment were 61.97%,46.93%,40.68% and 32.89%,showed that the pattern of 4 plantings had good water retention,water storage and soil conservation,and the strip pattern had the best effect.(3)Under the test conditions,as far as the runoff time was concerned,the runoff time of the bare slope was always the shortest,indicating that other pattern had the effect of delayed runoff time.The delay time was concentrated at 2~123 s,and the pattern of upper,lower,middle and strip were 37~79s,2~57s,15~73s and 59~123s,respectively.The relationship between the mean values was: strip pattern > upper pattern > lower pattern > middle pattern.As the flushing flow increased or the peak advanced,the runoff time of each slope was gradually shortened.(4)Under the test conditions,the four patterns of upper,lower,middle and strip had the benefits of flow reduction and sediment reduction,and the benefits of flow reduction were between 12.23% ~ 94.94%,and the benefits of the four were 14.73%~70.25%,12.23%~37.64%,12.88%~48.47% and 35.91%~94.94%,the mean value relationship was: strip pattern>upper pattern>middle pattern>lower pattern.The sand reduction benefit was between 12.92% ~ 98.87%,and the four sand reduction benefits were 40.70%~93.53%,12.92%~60.95%,27.42%~90.56% and 43.18%~98.87%,respectively.The mean value was: strip pattern>upper pattern>middle pattern>lower pattern.It was showed that under different water conditions,the strip pattern had the best effect of reducing and reducing sand in the four patterns.The strip pattern can be given priority in the prevention and control of soil erosion on the slope of the pile body and vegetation construction.(5)Under the test conditions,the content of silt in the eroded sediment particles was between 52.79 ~ 64.17%,the clay content was between 22.93 ~ 32.04%,and the sand content was between 7.15% ~ 24.28%,which relationship was: silt > clay > sand.For the particle enrichment rate,the silt and clay enrichment rate were slightly greater than 1,and the sand enrichment rate were less than 1,indicating that there was a small increase in the silt and clay in the eroded sediment compared with the test soil,but sand lower.In terms of particle agglomeration rate,the agglomeration rate of silt in each pattern was maintained at about 1,the agglomeration rate of clay was less than 1,and the agglomeration rate of sand was greater than 1,indicating that the silt and sand particles in the sediment were basically in the form of single particles,part of the clay was transported in the form of agglomerates. |
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