近饱和与非饱和土壤细沟水流输沙能力的对比研究

Comparison of Sediment Transport Capacity along Rills of Partially Saturated and Non-Saturated Soils

近饱和与非饱和土壤在水文、力学、结构等方面存在的差异可能会造成泥沙输移行为的不同。研究通过细沟模拟试验测定了近饱和与非饱和土壤在2、4及8L·min^-1三个流量和5°、10°、15°及20°四种坡度工况条件下的侵蚀过程,根据细沟剥蚀率与水流含沙量之间的关系解析得到相应的水流输沙能力,并采用试验验证解析值的合理性。通过方程模型量化近饱和与非饱和土壤水流输沙能力与水流功率之间的关系,在此基础上对比分析了二者水流输沙能力之间的差异。试验结果表明,解析得到的水流输沙能力与相同工况条件下的实测水流输沙能力间的差异为2%~6%。对数方程可以很好地表达近饱和与非饱和土壤水流输沙能力与水流功率之间的关系。各试验条件下近饱和土壤水流输沙能力是非饱和的1.08~2.35倍,表明土壤处于近饱和状态下更易发生侵蚀搬运。研究结果将有助于理解近饱和状态下土壤侵蚀水动力学机理,为完善土壤侵蚀物理模型提供理论依据。

The behaviors of partially saturated and non-saturated soils differ greatly in terms of their hydrology,mechanics,and structures,which may cause many differences during the process of sediment transport,and are therefore worthy of further in-depth study.In this study,a series of experiments was conducted to determine the sediment concentration of partially saturated and non-saturated soils at four slope gradients(5°,10°,15°,and 20°)and three flow discharges(2,4,and 8 L·min^-1).According to the model analysis of detachment rate and sediment concentration,the sediment transport capacity under corresponding hydraulic conditions was determined,and then the correctness of the analytical method was further verified by experiments.The equation model was used to quantify the relationship between sediment transport capacity and stream power.Then,the differences in the sediment transport capacity of partially saturated and non-saturated soils were compared and analyzed.The results showed that the difference between the analytical sediment transport capacity and the measured sediment transport capacity was 2%~6%,which indicated the correctness and rationality of the analytical method.The sediment transport capacity of partially saturated and non-saturated soils showed an increasing trend with an increased slope gradient and flow discharge.The logarithmic equation model can more accurately describe the relationship between the sediment transport capacity and the stream power.The sediment transport capacity of partially saturated soil was 1.08~2.35 times that of non-saturated soil,which indicated that the soil in partially saturation was more prone to erosion under the same hydraulic conditions.The research will help to understand the hydrodynamic mechanism of soil erosion under partially saturation and provide theoretical basis for improving the physical model of erosion.