Discrete element modeling of dry rock-ice avalanche impacts on rigid barriers: mechanisms and impact models

With the increase in environmental temperature, rock-ice avalanches originating from slope failures in alpine mountain areas have become a significant threat to the safety of key engineering projects. To enhance disaster mitigation capabilities, a detailed study of the impact dynamics of rock-ice avalanches is crucial, yet it has not been thoroughly investigated. A carefully calibrated DEM model is implemented in this research to systematically examine how ice-induced phenomena, including friction reduction and bulk density reduction, influence granular impact dynamics. Based on numerical data, new models are proposed to describe the impact behavior of rock-ice particle flows. The results indicate that the influence of ice content on granular impact dynamics is largely dependent on flow properties, as represented by the Froude number. Two primary effects—friction reduction and density reduction—account for the ice-induced impact behavior. The friction reduction effect dominates the granular run-up process, while the density reduction effect is responsible for the reduction in granular frontal impact. The body impact force is determined by the interplay between these two effects. Impact models should adequately consider the influence of the Froude number, Savage number, and ice content. Using the obtained numerical data, three models are proposed to predict run-up heights, frontal impact forces, and body impact forces. The presented results and models may serve as a critical basis for disaster mitigation design and back-analysis of rock-ice avalanche kinematics.