The landslide-river interaction and the impulse waves involved in the landslide dam formation process may not be insignificant and have not been extensively investigated and simulated. This paper presents a numerical investigation on the formation process of landslide dams and resulting free surface flow dynamics in the impacted river via coupled discrete element method (DEM) and computational fluid dynamics (CFD) with the volume of fluid (VOF). The accuracy and validity of the extended coupled method are verified using a series of test cases involving three-phase interaction and free surface evolution. It is then applied to simulate the landslide dam formation processes related to landslide and river flow scenarios of different kinematic characteristics. Furthermore, quantitative analysis is performed to describe the complex evolution of the dam morphology and dynamic evolution of impulse waves. It is found that the impact between the landslide, river flow and valley drives the dam formation process. The landslide velocity considerably influences the propagation of impulse waves, while the river flow velocities control the dam morphology in opposite ways in the upstream and downstream. This research provides a practical modeling framework to understand the formation mechanism of landslide dams and support applications in hazard prediction and mitigation.

滑坡大坝形成过程中涉及的滑坡-河流相互作用和冲击波可能不是无关紧要的，也没有得到广泛的研究和模拟。本文通过耦合离散元法 (DEM) 和计算流体动力学 (CFD) 与流体体积 (VOF)，对滑坡坝的形成过程和受影响河流中产生的自由表面流动动力学进行了数值研究。使用一系列涉及三相相互作用和自由表面演化的测试案例验证了扩展耦合方法的准确性和有效性。然后将其应用于模拟与不同运动学特征的滑坡和河流流动情景相关的滑坡坝形成过程。此外，定量分析描述了大坝形态的复杂演化和冲击波的动态演化。研究发现，滑坡、河流和山谷之间的影响驱动了大坝的形成过程。滑坡速度对冲击波的传播有很大影响，而河流流速在上游和下游以相反的方式控制大坝形态。本研究提供了一个实用的建模框架，以了解滑坡大坝的形成机制并支持在灾害预测和减轻中的应用。而河流流速在上游和下游以相反的方式控制大坝形态。本研究提供了一个实用的建模框架，以了解滑坡大坝的形成机制并支持在灾害预测和减轻中的应用。而河流流速在上游和下游以相反的方式控制大坝形态。本研究提供了一个实用的建模框架，以了解滑坡大坝的形成机制并支持在灾害预测和减轻中的应用。