Effect of impact velocity, block mass and hardness on the coefficients of restitution for rockfall analysis

One of the most significant input parameters in rockfall trajectory modelling is the Coefficient of Restitution, which controls block rebound. In particular, in the design of rockfall barriers, it can significantly affect their height. In practice, the coefficients of restitution are acquired by field or laboratory tests, back analyses of known events, experience or, most commonly, suggested values connected to the slope material. Furthermore, to account for the effect of impact velocity or block mass, scaling factors are available. However, the suggested values are based on a qualitative description of the slope material, and the scaling factors are not well documented, nor do they account for the effects of impact velocity and block mass simultaneously. In this paper, a semi-empirical correlation is proposed that takes into account the Schmidt hammer rebound value of both the slope and block material as well as the impact velocity and block mass. This was derived by an extensive laboratory experimental study (445 impact tests) of a one-dimensional drop of spherical blocks onto planar surfaces. The semi-empirical correlation proposed adequately describes the responses observed under the circumstances imposed in the laboratory.