Abstract:The intrusion of landslides into a river can block the river and induce surge waves. The evolution of the landslide-river blockage-surge wave disaster chain involves complex landslide-river interactions. To reproduce it realistically, an extended coupled discrete element method (DEM) and computational fluid dynamics (CFD) numerical method is proposed in this research: the VOF model is introduced to track the evolution of river free surface; a virtual sphere model is proposed to overcome the limitation of the critical size ratio of the mesh and particle; and the model is verified by several typical cases. Based on this, the simulation of the landslide-river blockage-surge wave disaster chain was carried out to reproduce the formation process of the Baige landslide-induced river damming, and the dynamic evolution process and interaction mechanism of landslide-river dynamics are investigated comprehensively. The results show that the proposed method can accurately simulate the landslide-river interaction during the evolution of landslide-river blockage-surge wave disaster chain; the landslide mass drives the propagation of surge waves, while the river significantly increases the kinetic energy dissipation of the landslide mass and has opposites effect on the deposition of the landslide along the flow directions; the simulated migration path, deposit morphology and wave erosion area of the Baige landslide are in good agreement with the field survey results, and the method successfully reproduces the October 11th, 2018 Baige landslide. The extended coupled DEM-CFD method proposed in this research provides a robust numerical tool for the understanding of the river blockage and impulse wave evolution mechanism, as well as the prediction of the disaster evolution process, which is of reference value for the of disaster emergency response and disaster mitigation strategies.