Large Rock Collapse-Induced Air Blast: Elucidating the Role of Geomorphology.

Rock collapse with large volumes can attain high speeds during their freefall motion. The impact of such a falling mass on the ground surface can initiate a powerful air blast with far-field destructive impact. To investigate the formation, disaster-causing mechanism and dynamic characteristics of rock collapse-induced air blasts, an existing coupled discrete-element method (DEM)–computational fluid dynamics (CFD) approach is employed on a rock collapse-generated air blast in Zengziyan, China (ZRC). The generated air blast shows a maximum velocity of over 50 m/s and subsequently dissipated rapidly. The high consistency between the simulated air blast dynamics and the video verified the DEM–CFD coupled method in the air blast modeling. Combined with the ZRC-induced air blast analysis, a simplified generalized model was designed to observe the potential effect of geomorphology. Results highlight the great contribution of geomorphology, to both air blast initiation and propagation. Collapsed rock mass with a free fall motion is prone to generate significant air blasts when colliding with the slope surface. Tremendous energy was transferred to the surrounding air at the moment. Compared with falling straight down, air blasts resulting from an airborne trajectory case show a longer propagation because the collapsed materials impart air a higher initial momentum parallel to the slope surface. In addition, air blast propagation in wide distribution areas in comparison to narrow valleys shows greater attenuation. This study will aid in understanding the mechanism of a rock collapse-induced air blast as well as the forward simulation of similar events for risk assessment. Highlights: DEM-CFD coupled method provides good performance in simulating the air blast dynamics. Large rock collapse with a free fall motion is prone to generate powerful air blasts when colliding with the slope surface. Geomorphology is greatly influential in both air blast initiation and propagation. [ABSTRACT FROM AUTHOR]