Impact failure and disaster processes associated with rockfalls based on three-dimensional discontinuous deformation analysis

Rockfalls, a common geohazard in mountainous areas, have destructive impact capacity and may cause failure of dangerous rock masses in their runout range. For slope risk assessment, a thorough understanding of the impact failure processes and dynamic characteristics associated with rockfall movements is necessary. The aim of this study is to investigate the impact of rockfall failure behaviours and disaster processes on the dangerous rock mass along the way through three-dimensional discontinuous deformation analysis (3D DDA). To validate the reliability and applicability of 3D DDA, numerous laboratory experiments are performed on the impact of downward moving blocks on the unstable block and block system (i.e. single block–single block, single block–block system and block column–block system models) by comparing the displacements, kinetic energies and movement states of blocks. Using the G318 national road in Tibet as an example, 3D DDA simulates the impact and disaster processes associated with upper rockfalls sourced from a complete giant block and multiple discrete blocks on lower dangerous rock mass. Further, rockfall failure modes, movement characteristics, block interactions and impact phenomena are investigated. Results show that 3D DDA can effectively simulate block movement and impact interaction. The upper rockfalls impact the initially stable lower dangerous rock mass, which is the triggering factor for failure of the lower dangerous rock mass. The blocks from the upper rockfalls interact and merge to move downward, increasing the total volume and impact capacity of the rockfalls. It has been discovered that the rockfall disaster caused by the impact of an upper rockfall comprising discrete blocks on a lower dangerous rock mass is more severe than that resulting from the impact of a complete block. Overall, the results of this research can be used to help predict and prevent rockfall disasters.