Analytic Determination of Soil Erodibility and Critical Shear Stress

摘要

An analytic method for determining the soil erodibility and critical shear stress τ_c of concentrated flow was advanced in the paper. Manipulating the functional relation of sediment concentration with rill length and the analytic method for detachment rate determination using the regressed functional relation with data from simulated erosion experiments, the relationship amongst maximum net detachment rate, soil erodibility and shear stress of the flowing water was derived from this function, and hence the soil erodibility and critical shear stress τ_c were determined. The results showed that soil erodibility is the same for the experimental soil of similar soil physical conditions under different slope gradients. Soil erodibility of silt-clay soil (Loess soil) is 0.3211 ± 0.0003 kg • N~(-1) • s~(-1) on average. Critical shear stress τ_c increases with the slope gradient, namely 3.191 N • m~(-2), 3.937 N • m~(-2), 4.127 N • m~(-2), 4.376 N • m~(-2), 4.624 N • m~(-2) under 5°, 10°, 15°, 20°, 25° respectively. The soil erodibility and critical shear stress τ_c thus computed were compared with those directly estimated on the basis of experimental data to verify the feasibility of this method. The paper advanced a quick and convenient yet feasible method to calculate the soil erodibility and critical shear stress τ_c.