坡面流输沙能力与土壤可蚀性参数对细沟土壤侵蚀过程影响的有限元计算模型研究

FINITE ELEMENT MODEL FOR CALCULATING EFFECTS OF SLOPE FLOW SEDIMENT TRANSPORT CAPACITY AND SOIL ERODIBILITY ON RILL EROSION PROCESSES

土壤侵蚀预报模型对于定量评价水土保持效果,合理制定水土保持措施等具有重要意义。细沟侵蚀模型是土壤侵蚀预报模型的重要组成部分。本研究建立了一个以物理概念为基础的细沟侵蚀预报模型,模型包括水流连续性方程、水流动力学方程和泥沙运移方程;同时,模型改进了部分参数的计算方法,以线性形式的水流输沙能力计算方法取代原有的对数形式方法,将土壤最大剥蚀率用于土壤可蚀性参数的计算;采用有限元方法对模型进行顺序求解;Visual C++语言数值计算程序被用来模拟细沟侵蚀产沙变化过程,并进行了一系列室内试验验证该数学模型、模型参数及数值计算方法。结果表明,模型预测值和实测值具有很好的一致性,改进的模型参数计算方法能够准确地反映土壤可蚀性参数与水流输沙能力对细沟侵蚀过程的调控作用。

Soil erosion prediction models are of great significances in formulating reasonable strategies for soil and water conservation. Rill erosion is an important component of hillslope soil erosion. To well understand and predict rill erosion is essential for hillslope erosion prediction. In this study, a physical-process-based model for predicting rill erosion is developed, encompassing water flow continuity equation, hydrodynamics equation, sediment transport equation, for a well-defined rill channel. Finite element model was used to numerically solve the hydrodynamic and sediment continuity equations. Rational model parameters were used in this simulation study. A series of case studies were conducted with parameters determined of a silty loess soil from the Loess Plateau of China to compare outputs of the model with spatial changes in sedimentation processes for a better understanding of rill erosion dynamics. The comparisons of the experimental resuits with the simulation outputs of the model were used to validate the model. The model is capable of simulating the dynamics of rill erosion processes, with good prediction performance. Therefore, the model is proven to be valuable for further development of the dynamic prediction model for temporal and spatial variation of rill erosion.