Impact of rockfalls on protection measures: an experimental approach

The determination of rockfall impact force is crucial in designing protection measures. In the present study, laboratory tests are carried out by testing the weight and shape of the falling rock fragments, drop height, incident angle, platform on the slideway, and cushion layer on the protection measures to investigate their influences on the impact force. The test results indicate that the impact force is positively exponential to the weight of rockfall and the instantaneous impact velocity of the rockfall approaching the protection measures. The impact velocity is found to be dominated not only by the drop height but also by the shape of rockfall and the length of the platform on the slideway. A great drop height and/or a short platform produces a fast impact velocity. Spherical rockfalls experience a greater impact velocity than cubes and elongated cuboids. A layer of cushion on the protection measures may reduce the impact force to a greater extent. The reduction effects are dominated by the cushion material and the thickness of the cushion layer. The thicker the cushion layer, the greater the reduction effect and the less the impact force. The stiffer the buffer material, the lower the buffering effect and the greater the impact force. The present study indicates that the current standard in China for designing protection measures may overestimate the impact force by not taking into consideration the rockfall shape, platform, and cushion layer