Slope instability is a common type of damage in embankment dams. Analyzing its microstructural changes during water transport is beneficial to identify the critical damage point in more detail. To this end, we closely link both diffused water molecule and damaged concrete. On the basis of the original research on fractal theory, the fractal permeability model for the pore system is established. At the same time, considering the pore structure characteristics of concrete, the models for fluid–solid coupling inside and outside the embankment are established in this work. The simulated results and experimental data agree well, thus verifying the correctness of the proposed models. The changes of concrete pore structures under different water pressure and different initial porosities are simulated by numerical methods. The results show that: (1) with the increase of the safety factor, the slope of the embankment begins to be damaged at the critical point and then completely destabilized; (2) with the increase of the pressure head, the change of the fractal dimension of the embankment’s porosity from the top to the bottom changes from linear to nonlinear. (3) The initial porosity of concrete is proportional to the evolution of concrete pore structure. From a technical point of view, this study can contribute the effective technical guidance for related professional practitioners in the analysis of embankment slope stability from a microscopic point of view.

边坡失稳是堤坝的常见损坏类型。分析其在水输送过程中的微观结构变化有利于更详细地识别关键损伤点。为此，我们将扩散的水分子和受损的混凝土紧密联系起来。在分形理论原有研究的基础上，建立了孔隙系统的分形渗透率模型。同时，考虑混凝土的孔隙结构特点，建立了路堤内外的流固耦合模型。仿真结果与实验数据吻合较好，验证了所提模型的正确性。采用数值方法模拟了不同水压和不同初始孔隙率下混凝土孔隙结构的变化。结果表明：（1）随着安全系数的增加，路堤边坡在临界点处开始发生破坏，进而完全失稳； (2)随着压头的增加，路堤孔隙度分形维数从上到下的变化由线性变为非线性。 (3)混凝土的初始孔隙率与混凝土孔结构的演化成正比。从技术角度来看，本研究可为相关专业从业人员从微观角度分析路堤边坡稳定性提供有效的技术指导。