Experimental Study On Characteristic Of Water Erosion And Soil Erodibility For Engineering Accumulation In Loess Area

The number of programs for production and construction increases along with thehigh-speed of our country’s social economy, and the waste soils and residues from theseprograms has become the main source of man-made soil and water losses. The soil and waterlosses caused by has a characteristic of high degree, extensive scope, severs harm andthreatens the soil and water resources and natural environment which humans rely on as wellas the development of social economy, ecological safety and the production and life of thepublic. Engineering accumulations is the main source of the man-made soil and water losses,and there is an important meaning for social reality and urgent social needs for a quick andaccurate calculation the quantity of soil and water loss. Soil erodibility factor is a basis forestablishing the prediction model. Our research takes the method which is the combination ofindoor artificial simulation of rainfall and the analysis of lab soil physicochemical properties,focusing on the water erosion characteristics and soil erodibility factor of engineeringaccumulation of the standard block (5m×1m、35°No vegetational cover) under the conditionof simulation of rainfall. Contrasting and analysing the characteristics and discrepancy of thehydrodynamic parameters. We compare the value K calculated by experiments andnomograph&EPIC methods, revising the present equation that calculate value K by thenomograph&EPIC method in order to make scientific soil and water conservation schemes,providing the basis for effective protection and treatment for man-made soil and water lossesand at the same time, making everyone relative clear of their responsibilities for the treatmentof soil and water losses, as well as providing scientific evidence and strong guarantee for thelaw enforcement and supervision of soil and water conservation. Main conclusions including:（1）Sediment yield characteristics under the condition of simulation of rainfall: velocityof runoff, runoff rate has manifested the trend of increasing first then staying stable with thevariation of runoff producing time, and infiltration rate, runoff sediment content and soildetachment rate show a trend of decreasing first then staying stable with the variation of thetiming of rainfall. When at the same levels of the ratio of soils and rocks, the velocity ofrunoff and degree of precipitation show quadratic function relevance, and infiltration rate,runoff rate and the degree of precipitation show linear relevance, while the runoff sediment content, soil detachment rate and the degree of precipitation show the relevance of powerfunction. There is a hysteretic nature between the sediment producing and runoff. The rocksand stones on the slope can restrain the hysteretic nature existing in water and sediment andhas a good relevance of power function between the sediment yield and quality of runoffunder the experimental condition.（2）The characteristics of hydrodynamic parameters: The Reynolds number varies from50-500in a experimental scope, Froude Number from0.4-1.15, runoff shear stress from4-20.Reynolds number, Froude Number, runoff shear stress show a trend of increasing sharply firstthen staying stable with the variation of the timing of precipitation. The flow resistance showsa trend of decreasing firstly the increasing with the rising of the degree of precipitation. Whenthe ration of soils and rocks and degree of precipitation are the same Reynolds number,Froude Number and resistance coefficient have a relevance of power function with degree ofprecipitation. Sediment yield, has a relevance of exponential function with Reynolds numberand Froude Number, and has a relevance of power function with runoff shear stress and flowresistance.（3）The calculation of soil erodibility factor. We get the value K of soil erodibilityfactor of pure soil,10%,20%and30%earth-rock volume is0.041、0.0385、0.0360、0.0242t hm~2h/hm~2MJ mm respectively, and the value K of soil erodibility factor isdecreasing with the content of rock is increasing.（4）The correction factor of nomograph method revising is1.89. The correction factorof revision of EDIC method is1.76.（5）The influencing factor of soil erodibility factor: The influencing factor of soilerodibility factor K of accumulation is the water content and volume-weight at the earlierstage. The increasing of soil erodibility factor K is a power function growth with theincreasing of water content at the earlier stage and the decreasing of soil erodibility factor K isa power function fall with the increasing of soil volume-weight.