| Various production and construction projects are increasingly implemented along withincreased investment in China’s infrastructure construction projects. In the process ofconstruction, plenty of vegetation is destroyed and surface and underground soils aredisturbed, detached and removed, which has caused serious man-made soil erosion and madeeco-environmental problems to become severe year by year. Because of illegal heaping andrandom dumping without any protective measure, massive waste soils and residues, i.e.,engineering accumulations, become the most serious places subject to soil and water loss andthe main sediment origins for the newly-added soil and water loss by human, which severelydeteriorates local eco-environment. In order to construct a soil and water loss calculationmodel suitable for production and construction projects in China, it is essential to refer to theideas involved in the Universal Soil Loss Equation (USLE) and revise such factors as soilerodibility, slope steepness, slope length and rainfall erosivity. At present, research on theseaspects still has many works to do in China. In this study, by taking the engineeringaccumulation of production and construction projects in the loess area as the research object,runoff yield, sediment yield and hydrodynamics on indoor simulated engineeringaccumulation were focused through an artificially simulated rainfall experiment. Specificobjectives were to understand the mechanisms of soil erosion and the processes of soil andwater loss and find the relational expression and the method to define fixed value for slopesteepness factor (S) incorporated in the soil and water loss calculation model. Our study mayprovide a scientific basis for the calculation model and the supervision and law enforcement by governmental departments in charge. The study is of important significance in science andpractical values in application. The main conclusions are as follow:(1) Under the condition of different soil textures, runoff rate and sediment transport rateare linear and power functions of rainfall amount, respectively. Runoff rate has a linearrelation with rainfall amount and slope steepness, while sediment transport rate, a powerrelation. The relationship between sediment transport rate and runoff rate can be describedusing exponential function.(2) Under the condition of different rainfall amounts, runoff rate has a linear relationwith slope steepness and a complex linear function with slope steepness and soil texture. Forrainfall amounts of45,90and112.5mm, sediment transport rate has significant complexliner relation with slope steepness and soil texture, while for rainfall amounts of90and112.5mm, there is a significant exponential relationship between sediment transport rate and soiltexture.(3) Under different slope steepnesses, runoff rate and sediment transport rate are linearand power functions of rainfall amount, respectively, but have no correlation with soil texture.Runoff rate and sediment transport rate are complex linear function of rainfall amount andsoil texture, respectively. There is an exponential relationship between sediment transport rateand runoff rate.(4) Runoff rate and sediment transport rate are significant linear and exponentialfunctions of rainfall amount, respectively, if slope steepness and soil texture are not taken intoaccount. Runoff rate and sediment transport rate are complex linear function of rainfallamount, slope steepness and soil texture.(5) For the same soil texture, both runoff shear stress and stream power increase withincreased rainfall amount. Unit stream power increases with increased rainfall amount andslope steepness. For the same slope steepness, both runoff shear stress and stream powerincrease with increased rainfall amount. Rainfall amount is the main factor affecting runoffshear stress and stream power. For the same rainfall amount, unit stream power increases withslope steepness and slope steepness has the greatest effect on unit stream power.(6) Runoff shear stress is complex linear function of rainfall amount, slope steepness andsoil texture, while stream power and unit stream power are complex liner function of rainfallamount, slope steepness and soil texture. The relationships of soil detachment rate with runoffshear stress, stream power and rainfall amount can be described using exponential function,respectively. Soil detachment rate is quadratic function of unit stream power and the Froudenumber (Fr), and power function of the Reynolds number (Re) and resistance coefficient (f),respectively. The optimal curve fittings for the relationships between soil detachment rate and the hydrodynamic parameters are in the descendant order of rainfall amount, stream power,unit stream power, Fr, f, runoff shear stress and Re. Soil detachment rate is complex linerfunction of rainfall amount, slope steepness and soil texture.(7) For the first time, the standard plot and slope steepness factor used in the watererosion calculation model are defined in combination with the characteristics of theengineering accumulation. The standard plot adopted for the research on soil and water lossesfrom various engineering accumulations in China is defined as the bare plot with a length of5m and a slope steepness of35o. The slope steepness factor S is defined as the ratio of soil lossfrom a specific engineering accumulation to that from the engineering accumulation of35oslope steepness, when other conditions are identical.(8) A check spreadsheet of the S values for the slope steepnesses of15o to44o isestablished using the power and trigonometric equations of slope steepness factor obtained byregression fittings. |
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