Geotechnical and kinematic parameters affecting the coefficients of restitution for rock fall analysis

This paper presents the results of laboratory and field tests regarding the determination of the parameters that influence the trajectory of falling blocks in rockfalls. Coefficients of restitution are considered to be critical parameters in rockfall modeling, but various definitions exist and there is no agreement on which one is more appropriate. In this research, the lamped-mass analysis method was used and coefficients of restitution were calculated using the kinematic definitions. The laboratory testing was performed using a number of common rocks found in Greece. The rock materials tested were characterized by different Schmidt hammer rebound hardness values while the mass of the falling blocks as well as the impact angle and the velocity were altered during the tests in order to estimate the effect of each parameter on the coefficients of restitution. The kinematic coefficient of restitution was compared to the normal coefficient of restitution and was found to be more appropriate when used in correlations. Impact angle was found to significantly affect the trajectory. Finally, a correlation between Schmidt hammer rebound hardness and kinematic coefficient of restitution is proposed whilst a method for estimating the normal coefficient of restitution is suggested including the impacts' angle effect. (C) 2012 Elsevier Ltd. All rights reserved.