Experimental Study On Character Of Ephemeral Gull Occurred And Dynamic Process On Loess Plateau

The ephemeral gully erosion of slope surface occupies is an important position in the soil erosion of the loess plateau, which is the slope surface to mainly erode one of the ways, it is also the main part that the slope surface produces a sand. The ephemeral gully erosion quantity's hazing the ditch ground is 35-70% percent of with erosion, the loess plateau soil erosion is one of the serious main sources. Currently the slope surface most paths flow small area, the measurement slice eclipse, the thin ditch erosion quantity did not include ephemeral gully erosion, as a result to used for evaluating the slope surface erosion quantity low, most soil erosion forecast the model also didn't consider the influence that the ephemeral gully erode. Therefore to the loess plateau slope surface the ephemeral gully erosion produce the sand process and its water motive characteristic carry on fixed amount of on trial research, not only announce to public the loess mound area slope surface erosion regulation towards go deep into, protection the land resources and decrease flow into the yellow river sediment to have important production actual meaning, and to establishment the soil erosion forecast the model and certain ascent ditch manages policy to has important science meaning and application value. This paper postpones Anne the Yaner ditch river valley in the north shaanxi. Turning on water to flush to experiment through an open country, the erosion that studied a different slope, dissimilarity to turn on water the discharge circumstance to go down slope ephemeral gully of surface to erode produces the variety regulation of the sand and the water motive parameter, the main research result for obtain is as follows:1. Ephemeral gull erosion existed extreme number phenomena in the soil erosion changing with the variety of the slope.The changing of runoff volume, the sediment rate, runoff sediment, concentration, the sediment yield was parabola curve in the experiments, the critical slope gradient was about 18.5°-29°. If slope gradient was lower than critical slope, the parameters increased with slope gradient increasing, when more than the slope gradient, the parameter decreased with slope gradient increasing.2. The variety of ephemeral gull sediment soil and hydrodynamic parameter with the variety regulation of timeThe sediment concentration, the Reynolds number, Froude number decreased with the time went on in different discharge a slope gradient. The Reynolds number, the Darcy-Weisbach friction dynamic parameter increased with time passing. The rate of runoff number did not change much more with time elapse. Sediment yield had power relationship with the runoff and discharge. Seted up the equation bout the relationship of Sediment rate and time.3.The influence that the sediment production, runoff the hydrodynamic parameter to ephemeral gull erosion with Up-slope Runoff and SedimentThe Up-slope Runoff and Sediment, runoff rate, velocity of flow, Reynolds number are all obviously aggrandizement of the ratio than non Up- slope Runoff and Sediment's. Froude number, sediment-producing rate increased Along with the aggrandizement of the Up-slope Runoff discharge, that decline with the aggrandizement of the sediment concentration of the Up-slope Runoff discharge. The Darcy-Weisbach friction of the Up- slope Runoff and Sediment is smaller than the Darcy-Weisbach friction of the non Up- slope Runoff and Sediment,and along with Up- The slope Runoff enlarge, the Darcy-Weisbach friction let up. With the condition of Up- Under slope Runoff and non Up- Under slope Runoff, The relationship of Re and f Become reduces function, Re and Fr become increase function.4. The influence of the ephemeral gull erosion yield under the condition of the converting flux the runoffChange the discharge in front and back: runoff rate, sediment-producing rate, and current velocity with turn on flux runoff line positive related. The increase the quantity runoff rate before changing the discharge is more than that of the variety rate of the discharge. Contain t sediment concentration with turn on flux runoff the parabola form variety. Darcy-Weisbach friction with turn runoff the power function relation, Darcy-Weisbach friction decrease with the enlarge runoff. The relationship of Froude number, Froude number and runoff become the positive related line function. Re, Fr variety quantity before enlarge runoff is more digger than that of enlarge runoff.There is a common point that the influence of the runoff upon the runoff rate, sediment-producing rate, sediment yield, sediment concentration, velocity of flow, Reynolds number, Darcy-Weisbach friction, Froude number. The common point is that before converting flux runoff the influence of sediment yield and hydrodynamic parameter is much more than that of change runoff. This conclusion tells us that rainfall runoff and scouring runoff contribute to the erosion sediment yield is tremendous in the beginning.5.The influence of the sediment yield and the hydrodynamic to ephemeral gull erosion yield with cultivationThe rate runoff diminished after cultivation,decrease 19%～21% on the slope of the same gradient. Sediment yield is as 1-12 time as non-cultivation. Sediment concentration by cultivated bigger than no cultivate during the 0-20 minutes, sediment concentration in cultivation is equal to non cultivate in 20-40 minutes. Sediment concentration has great increased in cultivation than non-cultivate. Under the different discharge, accumulation sediment concentration Increased 53%-178%. By the cultivation and non-cultivate Trial treatments, accumulation sediment concentration had power relationship with volume of runoff and runoff.The velocity of flow ephemeral gull runoff decline in cultivation, And at any time a variety is more even slow. Darcy-Weisbach friction had become the inverse ratio relation with time and discharge. Under the condition of same discharge, Froude, Reynolds number number steady after the cultivation.