Navier-Stokes水流与Brinkman-Darcy渗流耦合对宽级配土坡失稳的力学效应

雨季山区常出现“群发性”的浅层滑坡，物质组成具有典型宽级配土特征；这类滑坡往往伴生大范围水土流失、形成大面积灾后创面。以往稳定性评价常忽略水流拖曳力效应，很少考虑坡面水流与坡体渗流耦合对土坡失稳的联合作用。为此，建立坡面水流-坡体渗流耦合数学模型，坡面水流遵循Navier-Stokes（N-S）方程，坡体渗流用Brinkman-Darcy（B-D）公式描述，引入Neal-Nader边界和Ochoa-Tapia-Whitaker边界来定解，推求N-S水流与B-D渗流耦合的流场解；结合Newton内摩擦定律评价水流的细观力学效应，探讨水流对宽级配土坡失稳的力学作用机制，进行模型试验、数值计算、案例反馈一致性检验；求解的水流拖曳力嵌入现有稳定性评价方法，定量评价拖曳力对土坡颗粒启动-滑移扩展的演变过程，分析水流有关的因素对土坡失稳的敏感性，为N-S水流和B-D渗流作用下土坡失稳机理研究提供支撑。

In rainy seasons every year, groups of shallow landslides often occur in mountainous areas. The material of the shallow landslides is characterized by widely-graded soil. Substantial slope failures would lead to large-scale soil erosion, and large-area naked sliding surface as well. The drag force effect of water-flow on slope surface and in slope was often ignored when evaluating the stability of this kind of landslide in the past. Moreover, the mechanical effect of a water-flow on slope surface coupled with seepage in the slope or landslide was rarely taken into account in the reported literatures. A nonlinear theory model coupling water-flow on slope surface and seepage in slope is established in this work, and the movements of water-flow and seepage obey the Navier-Stokes equation (N-S) and the Brinkman-Darcy equation (B-D), respectively. The solutions of slope flow field can be obtained by separately applying Neal-Nader’s continuous boundary condition model and Ochoa-Tapia-Whitaker’s stress boundary condition model. The micro-mechanical effect of water-flow can be quantified together with Newton’s internal friction law. The mechanical effect of water-flow on widely-graded soil failure can be discussed as well. The theoretical analysis results of drag force can be validated by indoor model test, numerical calculation and case feedback. The obtained drag force of water-flow on slope surface could be embedded into the stability evaluating method to illustrate the process of particle movement and sliding failure of the widely-graded soil slope, and to analyze the sensitivity of parameters related to water-flow on the widely-graded soil slope failure. The research results of this work could provide theoretical support for failure mechanism of the widely-graded soil slopes under the influence of N-S water-flow and B-D seepage.