A collision fragmentation model for predicting the distal reach of brittle fragmentable rock initiated from a cliff

Collision-induced fragments from large volume isolated rock block collapsed from cliffs with heights of hundreds of meters could cause greater distal reaches via superimposing additional velocities on the frontal smaller fragments at the impact zone. These fragments may pose significant threats to distant infrastructure, life, and property due to their extremely high velocities and disastrously long runouts. To reveal the collision fragmentation mechanism on the evolution of higher velocities fragments and predict the distal reach of the frontal smaller ones, a two-dimensional block-terrain impact model of an intense brittle rock block colliding onto a rigid plane is proposed. Furthermore, the well-documented experiments on collision fragmentation of brittle chalk were used to verify the derived mathematical equations of the model. The results indicated that the calculated results can match experimental data well. The proposed model can provide meaningful insights into the kinetics of fragmental rockfalls and enable predictions of the possible distal reaches of explosive fragments, which are crucial for hazard zoning and mitigation design.