Numerical modeling of slope failures seeks to predict two key phenomena: the initiation of failure and the post-failure runout. Currently, most modeling methods for slope failure analysis excel at one of these two but are deficient in the other. For example, the Finite Element Method (FEM) models the initiation of instability well but quickly loses accuracy when modeling large deformations because of mesh distortion, restricting its ability to predict runout. Conversely, the Material Point Method (MPM) utilizes material points which move freely across a background grid, allowing for indefinite deformations without computational issues. However, MPM is restricted in its ability to model slope failure initiation due to limitations of the available boundary conditions and reduced accuracy of its stress distributions. The sequential hybridization of these two methods, initiating a model in FEM and then transferring to MPM, presents an opportunity to accurately capture both initiation and runout by a single model. The exact time for this transfer is not self-apparent, but it must be conducted after the initiation mechanism and before excessive mesh distortion. By simulating two granular column failures and two slope failures, we demonstrate the effectiveness of this hybrid FEM-MPM method and identify the appropriate time to transfer.

翻译：边坡失稳的数值模拟旨在预测两个关键现象：破坏的起始与破坏后的运动堆积。目前，大多数边坡失稳分析建模方法在两者之一表现优异，但在另一方面存在不足。例如，有限元法（FEM）能很好地模拟失稳起始过程，但在模拟大变形时因网格畸变会迅速丧失精度，从而限制其预测运动堆积的能力。反之，物质点法（MPM）利用物质点在背景网格上自由移动，允许无限制的变形而不会产生计算问题。然而，由于可用边界条件的限制及其应力分布精度降低，MPM在模拟边坡失稳起始方面能力受限。将这两种方法顺序混合——在FEM中启动模型，然后转换至MPM——为通过单一模型精确捕捉起始与运动堆积提供了可能。这一转换的确切时机并非不言自明，但必须在起始机制形成后、网格过度畸变前进行。通过模拟两个颗粒柱坍塌和两个边坡失稳案例，我们验证了这种混合FEM-MPM方法的有效性，并确定了合适的转换时机。