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Wildfires are becoming a global natural disaster under climate change. A worthwhile concern is that the rainfall thresholds that trigger debris flows in catchments affected by recent wildfires are much lower than those that trigger debris flows in catchments with similar environments but that have not experienced wildfires. In this study, we investigated a major post‐fire debris flow event in Xiangjiao catchment triggered by heavy rainfall in 2021. Through the combination of field observation, laboratory experiments and several numerical models (rainfall interception, infiltration, erosion and runoff models), the physical mechanistic analysis and numerical simulation of the post‐fire debris flow in Xiangjiao catchment was carried out. Results show that the simulated deposited area, erosion depth, and the occurrence time of debris‐flow initiation correlate well with the actual situation. It is demonstrated that the numerical simulation method used in this study can be used to effectively describe the characteristics of the initial and propagation stages of the post‐fire debris flow generated by runoff and provide important insights and guidance for the prediction and prevention of debris‐flow disasters in catchments affected by wildfire. Plain Language Summary: Wildfires are becoming more and more common under more frequent extreme weather. After the wildfire, the overall environment would be substantially changed, which will lead to more frequent debris‐flow disasters. Consequences of these changes are worthy to be deeply investigated. In this study, we investigated a major 2021 post‐fire debris flow event in Xiangjiao catchment, China, triggered by heavy rainfall. Through the combination of field observation, laboratory experiments, and numerical models, the physical mechanistic analysis and numerical simulation of the post‐fire debris flow in Xiangjiao catchment was carried out. Key Points: The mechanism of post‐fire debris flows caused by runoff in Xiangjiao catchment is analyzedUsing multiple numerical models and multi‐source data, the 2021 Xiangjiao post‐fire debris flow is simulatedThe numerical simulation results are analyzed and correlated well with the field investigation [ABSTRACT FROM AUTHOR]

To investigate the movement mechanism of debris flow, a two-dimensional, two-phase, depth-integrated model is introduced. The model uses Mohr-Coulomb plasticity for the solid rheology, and the fluid stress is modeled as a Newtonian fluid. The interaction between solid and liquid phases, which plays a major role in debris flow movement, is assumed to consist of drag and buoyancy forces. The applicability of drag force formulas is discussed. Considering the complex interaction between debris flow and the bed surface, a combined friction boundary condition is imposed on the bottom, and this is also discussed. To solve the complex model equations, a numerical method with second-order accuracy based on the finite volume method is proposed. Several numerical experiments are performed to verify the feasibilities of model and numerical schemes. Numerical results demonstrate that different solid volume fractions substantially affect debris flow movement. [ABSTRACT FROM AUTHOR]

Large-diameter anchors are one of the important connection components in the reinforcement of industrial facilities. In the present study, a finite element (FE) model of large-diameter post-installed anchor system is appropriately established to investigate its pull-out performance and failure modes observed in the prototype experiments. The applicability of the proposed model is discussed through comparison of its results with experimental results (e.g., in terms of the ultimate load, corresponding displacement, and failure modes), and the parametric sensitivity based on the numerical results is studied. The results showed that the pull-out behavior could be well simulated using the proposed model. The progressive failure evolution process of the large-diameter anchor can be revealed by computational load–displacement curves. Thus, the proposed model of a large-diameter post-installed anchor can enable reliable design of anchor systems for industrial reinforcements. [ABSTRACT FROM AUTHOR]

This study used a three-dimensional model based on the finite-discrete element method-smoothed particle hydrodynamics (FDEM-SPH) coupling approach to reconstruct the 11 October 2018 Baige landslide that blocked the Jinsha river. The numerical model simulated the dynamic process of the landslide by FDEM, while the SPH simulated the behavior of the river water. The landslide deposit area and the water-eroded area in the FDEM-SPH simulation agree well with the results of the field investigation. According to the simulation, the main duration of the Baige landslide was 80 s. The peak average speed of the landslide was 34.4 m/s, while the local speed of the sliding mass reached a maximum velocity of 70 m/s. The tensile effect and the shear effect caused isotropic dispersive stress which caused the dynamic and violent fragmentation of the landslide. The model also simulated the variation of kinetic energy, the accumulated friction dissipation, and the fracture energy of the sliding mass with time. After the sliding mass ran into the river, the landslide triggered a wave, which rapidly dispersed due to the subsequent mass movement. The front part of the sliding mass pushed some of the river water to the opposite bank where the wave reached a height of 120 m. The results of the FDEM-SPH model, the particle flow code (PFC) model, and the depth-integrated shallow-water flow (DISWF) model are compared and analyzed concerning studying landslides that block rivers. Three types of evolution mechanisms of high-level flow-like landslide-induced waves in deep river valleys are proposed in this paper. • A novel fluid-solid coupling approach based on FDEM-SPH is used for landslide blocking river. • Dynamic process of the Baige landslide blocking river is shown clearly. • Evolution modes of high-level fluid-like landslides blocking rivers in deep valley area are proposed. [ABSTRACT FROM AUTHOR]