In this paper, we report on the simulation study of a new rock fall algorithm. This algorithm takes into account the geometric shape and 2-D rigid body dynamics of the falling rocks. Earlier simulation studies have been done with a point rock mass model. The introduction of rock shapes different from circular makes the simulation more realistic. The shape and size change the contact kinematics and impact dynamics. This in turn has a significant influence on the impact distance calculation. Moreover, the combined effect of shape variation of the falling rock block and the slope irregularities adds an interesting dimension to the final impact distance variation.
Rock falls occur when rocks break away from a slope. The release mechanism can be natural, such as during the freeze-thaw cycle, or anthropogenic, as in an open-pit mine or rock quarry. While the rockfall mechanism can be quite complex, an in-depth understanding of the mechanism is important in several ways. During the design stage, carefully designed rock cuts can minimize the hazardous rock fall range. In terrains where there are rock fall activities, properly designed protection systems can minimize or eliminate the danger to people and vehicles in highways and mines. Furthermore, a good understanding of rockfall trajectories can be useful in the determination of the height and energy capacity of rockfall barriers. The ability to model rock fall events accurately allows a designer to construct rock fall mitigation measures such that risk to human life and business is reduced. Rock fall trajectory simulation plays a crucial role in the understanding of natural and man-made rock fall hazards. The physics behind the dynamics of falling bodies and their collision with other bodies and surfaces is well understood. However, what sets rockfall simulation apart from similar physics simulations is the uncertainty and large variability of physical parameters such as coefficients of friction and normal coefficient of restitution. Rocks come in various shapes and sizes. Rock slope surfaces are rugged and materially inhomogeneous. In such situations deterministic analyses are rather futile. A proper understanding requires statistical analyses. Statistical analyses of trajectories require the outcome from thousands of projectiles. In practice, these computer simulations should be performed simultaneously. Investigators studying rockfalls have identified four types of motions associated with the trajectories: free fall under gravity, bouncing, sliding and rolling. Models that simulate the trajectories need to incorporate these motions. Thousands of rockfall trajectories incorporating all possible motions over a complex mountainous terrain would increase the computation time considerably. In order to keep the computation time reasonable, most rockfall simulations are performed with lumped mass models. The lumped mass models assume that the rock mass is concentrated at the centre of gravity. The disadvantage of this approach is that the rotational energy of the rock mass is not accounted for properly. For the same reason, rolling cannot be realistically simulated. In the new rock fall model that has been developed at Rocscience Inc., we have introduced several innovations to incorporate finite sized rock masses with arbitrary shape while maintaining fast computation times similar to the lumped mass model.
