## 2 Identification of Slip Pathways in Dam Slope  
The failure modes of embankments mainly include seepage failure, landslide instability, structural instability, and overflow failure. seepage failure is one of the core threats to dam safety, which is manifested in the forms of pipe surge, soil flow, contact erosion, and osmotic collapse. For example, pipe gushing is caused by the continuous erosion of fine particles under the action of seepage to form a penetrating channel, while the flow soil is the overall floating or loss of local soil due to the action of permeability, and this kind of damage often occurs in the heterogeneous soil layer or the weak part of the anti-seepage structure. Landslide instability is mostly caused by steep slopes, insufficient soil strength or external loads (such as sudden drop in water level and earthquakes), which is manifested as a large-scale slide of the dam along the potential sliding surface. Structural instability is associated with material aging, uneven settlement, or overloading, which can lead to crack propagation or even overall collapse. In addition, flooding will directly wash away the downstream slope of the dam, resulting in a sudden increase in the risk of dam failure. In view of the above problems, a variety of numerical simulation methods are often used in engineering for stability analysis and seepage simulation. As a traditional method, the limit equilibrium method (LEM) evaluates the overall stability of the slope by assuming the sliding surface (such as the arc) and calculating the safety factor, which has the advantage of efficient calculation and few parameter requirements and is widely used in preliminary design, but it cannot consider the details of soil deformation and the coupling effect of seepage. The finite element method (FEM) can simulate complex working conditions more finely, such as analyzing the seepage field distribution through Darcy's law coupled with the unsaturated seepage model, combining the elastoplastic constitutive model to study the stress-strain response of the dam, and using the Biot theory to realize the fluid-structure interaction analysis of seepage and deformation, so as to reveal the progressive failure mechanism under the sudden drop of water level or seismic load. However, FEM is highly dependent on material constitutive models and computational resources. The discrete element method (DEM) and particle flow method (PFC) focus on the meso-scale and visually demonstrate the microscopic mechanisms, such as soil particle migration and skeleton reconstruction, in the pipe surge process by simulating the mechanical behavior of inter-particle contact, which is suitable for studying the local seepage failure or collapse process. However, its calculation cost is high, and the microscopic parameters need to be calibrated by experiments. In practical engineering, LEM and FEM are often combined to improve efficiency and accuracy (e.g., FEM is used to analyze the seepage field, and then LEM is used to calculate stability), while DEM is mostly used for mechanism studies or the detailed simulation of key parts. In this study, the finite element method was used to calculate the slip channel of the dam slope in combination with a elastoplastic constitutive model of the soil. The elastoplastic finite element method is based on the mechanics of soil elastoplasticity, overcoming the limitations of the rigid body limit equilibrium method, which cannot account for the nonlinear stress-strain behavior of soil. Additionally, it considers the effects of initial stress, stress pathways, and material anisotropy while accurately modeling complex geometric boundaries, dam structures, and dam construction and reservoir impoundment processes. Consequently, this method provides a more realistic representation of the stress distribution and failure states of soil under loading conditions.