Normal restitution coefficient of sandstone spheres

The normal restitution coefficient (NRC) is a key parameter that determines the trajectory of the stone during a rockfall. In this study, using a test equipment and a sound-sampling technique developed by ourselves, we first measured the NRC of sandstone spheres and analyzed its influencing factors, i.e. the particle size, the impact velocity, the hydrous state and the elastic properties of the plate, and then we examined the size effect, the rate effect and the energy dissipation mechanism of the NRC. The results show that the NRC of sandstone spheres has a complex size effect which, with the increase of the size of sandstone spheres, at first increases and then decreases. The analysis shows that there exists two energy dissipation mechanisms, i.e. the viscoelastic dissipation and the elastoplastic damage dissipation, interacting with each other, which result in the complex size effect; that, due to the heterogeneity of sandstones, the velocity effect of the NRC is obvious when the diameter of the sandstone particle is small, while this effect is unobservable when the diameter is over 5 cm; that, compared with the NRC of air-drying sandstones, the saturation can cause the viscoelastic dissipation and elastoplastic damage dissipation to increase; and that the equivalent elastic modulus has a great impact on the NRC, i.e. the greater the equivalent elastic modulus, the smaller the NRC.