An Experimental Research On Sediment Transport Capacity Of Rill Flow On Colluvial Deposit Slope Of Benggang

The key of the simulation of soil erosion is to estimate the sediment transport capacity of rill flow correctly,however the influence of gravel content on rill flow sediment transport capacity is not yet clear.This study chose soil-rock mixed colluvial soil from Anxi county of Fujian Province.The experiment used the test by adding sand in rill head,adopted three factors experiment design,set up four different slope gradient(17.63%,36.40%,57.74%,83.91%),five different flow discharge(0.00028,0.00056,0.00111,0.00222,0.00444 m2/s)and six different gravel content(0%,10%,20%,30%,40%,50%).This study anaylized thesediment transport capacity of rill flow in different hydraulic condition,and studied the mechanism of gravel content on rill flow sediment transport capacity,set up hydrodynamic models of sediment transport capacity.The main conclusions were as followed:(1)Rill flow sediment transport capacity increased with flow discharge at different slope gradient and could be described by power functions.At different flow discharge,when flow discharge was ranged from 0.00028 to 0.00056 m2/s rill flow sediment transport capacity increased with slope gradient and could be described by exponential functions,while flow discharge ranged from 0.00111 to 0.00444 m2/s,rill flow sediment transport capacity increased with slope gradient by logarithmic functions.At different slope,most of rill flow sediment transport capacity increased by exponential functions with gravel content,however,when flow discharge was 0.00028 m2/s,rill flow sediment transport capacity changed by binomial functions with gravel content at slope of 17.63%,and rill flow sediment transport capacity increased first and then decreased with gravel content by binomial functions at slope of 36.40%.At different flow discharge,when flow discharge ranged from 0.00028 to 0.00056 m2/s,rill flow sediment transport capacity changed a little with gravel content by binomial functions;while flow discharge ranged from 0.00111 to 0.00444 m2/s,rill flow sediment transport capacity increased with gravel content by exponential functions.Under the involved conditions,the effect of three factors on rill sediment transport capacity was showed as followed:flow discharge>slope gradient>gravel content(median diameter).The factorial model for sediment transport capacity(Tc)could be estimated using a power function of flow discharge(q),slope gradient(S),and median diameter(d50),the power function was Tc=3523.98S0.269q0.998d500.117.(2)At different flow discharge or slope gradient,flow depth,Reynolds number,resistance coefficient,flow shear stress and stream power increased with gravel content.However,flow velocity,Froude number and unit stream power decreased.The factorial model for flow velocity,flow depth,Reynolds number and Froude number could be estimated by a power function or a linear function of flow discharge,slope gradient,and gravel content or median diameter;the factorial model for resistance coefficient,flow shear stress,stream power and unit stream power could be estimated using a power function of flow discharge,slope gradient,and median diameter.The effect of flow discharge on flow velocity,flow depth,Reynolds number,flow shear stress,stream power and unit stream power did most,slope gradient did less,and content gravel(median diameter)did the least.Moreover,slope gradient had greatly influenced on Froude number,flow discharge secondly,and gravel content(median diameter)was smallest;the effect of flow discharge on resistance coefficient was the greatest and gravel content(median diameter)secondly,and slope was the smallest.(3)At different gravel content,rill flow sediment transport capacity increased by power functions with rill flow velocity;rill flow sediment transport capacity increased by linear functions with flow shear stress,stream power and unit stream power.Flow shear flow was the best hydrodynamic parameter to describe rill flow sediment transport capacity under experimental conditions,the factorial model for sediment transport capacity(Tc)could be estimated using a linear function of flow shear stress(?),the linear function was Tc=0.118(?-3.92).