| Dongzhiyuan has extremely valuable land resources and agricultural production conditions.However,the long-term serious headward Erosion has been caused serious consequence to the security of Dongzhiyuan.It has become a serious hidden danger of the local ecological construction and the sustainable development of the economy and society.Study on erosion process and hydraulic parameters characteristics of Dongzhiyuan headcut erosion can further reveal the mechanism,lay an important foundation for the research on the model of gully erosion process,provide an important scientific basis for the realization of land resources of Dongzhiyuan in Loess Plateau of effective management and scientific management of soil and water loss.In this paper,the situ headcut erosion models with different slopes and headcut heights were established in Nanxiaohegou,west of Loess Plateau.An artificially simulated rainfall and runoff scouring experiment was carried out to investigate the effects of slope,headcut height and flows to the runoff and sediment yielding process and hydraulic process.The main conclusions are as follows:(1)Soil buck density were 1.23-1.30 g/cm~3 during different soil depth,the average soil bulk value was 1.26 g/cm3.Soil bulk density increased with increase in soil depth.Soil moisture content of bare were 10.54%-13.18% while the average value was 11.77%.Soil moisture content increased then decreased with the increase in soil depth.Soil cohesion and internal friction angle were 14.92 kPa and 13.22°,respectively,both decreased with the increase of moisture content.Comparing to the moisture content was 6.53%,while the moisture content got to 15%,soil cohesion and internal friction angle decreased 6.83% and15.6%,respectively.While moisture content got to 20%,the soil cohesion and internal friction angle decreased 26.11% and 28.6%,respectively.Soil disintegration rate increased with the increase of soil depth.Compared to the layer of 0-10 cm,the others layer increased 253.42%?222.28%?380.40% and 481.81%,respectively.(2)While the slope was 3°,the headcut was 0 m and the slope was 6°,the headcut was1.5 m,the runoff was increased with the flows increased.While the slope was 3°,the headcut was 1.5 m and the slope was 6°,the headcut was 0 m,runoff rate was increased with the flows increased from 100 L/min to 300 L/min.Runoff rate was found to be a exponential function and a po wer function,respectively.The influence of runoff was more significant than slope and headcut height.Runoff rate with the plot of 3°was higher than 6°.While the headcut was 0m,the runoff volume of 3°was 6222.65 L,16214.4 L,23198.11 L,31707.77 L,respectively.Runoff volume was found to be a linear function and a power function with 3°and 6°And runoff volume of 6°was 7986.01 L,9286.34 L,16394.63 L,13182.1 L,runoff volume was found to be a linear function and a power function,respectively.With the headcut height was1.5 m.Runoff volume was found to be a power function and a linear function with 3°and 6°.(3)While the headcut height was 0 m,sediment concentration with slope of 3° was99.98 kg?368.95 kg?586.70 kg?806.06 kg and 353.65 kg?463.88 kg?654.52 kg?849.94 kg with flows increased.Sediment concentration was found to be a linear function with flows.For the headcut height was 0 m,sediment yield increased slower with the flows increased57.59% with the flows increased from 100 to 200 L/min.Headcut was 1.5 m,the peak value of sediment concentration was occurred in 15 min after runoff generation in the second souring experiment and 45-50 min after runoff generation in the second souring experiment.Parabolic erosion generated in the side wall of gully with headcut height increased caused sediment yield increased.(4)Headcut height was 1.5 m,the velocity was 0.75 m/s?0.85 m/s?0.95 m/s?0.99 m/s and 0.85 m/s?1.15 m/s?1.06 m/s?1.05 m/s with slope was 3° and 6°.While the slope was 3°,velocity was found to be a linear function with flows.Velocity of 6°increased while the flow increased from 100 to 200 L/min.Runoff was belong to turbulence flow.Headcut height was1.5 m,sheer stress was 1.71 N/m~2?1.92 N/m~2?2.75 N/m~2 and 1.95 N/m~2?2.71 N/m~2?2.96N/m~2?1.37 N/m~2 at 2 slope.Sheer stress was found to be a linear function and a logarithm function with flows in two slopes.Headcut height was 1.5 m,stream power was 1.27 W/m~2?1.63 W/m~2?2.61 W/m~2?2.84 W/m~2 and 1.05 W/m~2?1.19 W/m~2?1.56 W/m~2?1.56 W/m~2at2 slope.Stream power was found to be a linear function while the slope was 3°.Stream power was found to be a logarithm function while the slope was 6° at the flows was 100 to 300L/min.Headcut height was 1.5 m,unit stream power was 0.039 m/s?0.045 m/s?0.050 m/s?0.052 m/s and 0.039 m/s?0.047 m/s?0.052 m/s?0.055 m/s at 2 slope.Unit Stream power was found to be both a logarithm function while in two slope.Sediment yield was more interrelated with stream power compared to other hydraulic parameters. |
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