Experimental study of artificial blocks under dynamic fragmentation

Rockfall represents a significant hazard not only in mountainous areas, but also alongside coastal routes, major transport infrastructures and quarry faces. One aspect of the rockfall phenomenon that still requires further investigations is the fragmentation of falling blocks upon impact. The changes in size, shape and energy of the falling blocks upon fragmentation and the variation in trajectory of the fragments can seriously affect the optimization design of the rockfall mitigation measures. The fragmentation of boulders during a rockfall event can lead to significant changes in the global run-out distances and the maximum kinetic energy to be accounted in the protection systems design. This thesis presents an experimental program conducted to investigate the fragmentation phenomenon under controlled conditions to provide some useful insights in terms of block survival probability upon dynamic impact, fragments distribution, post impact velocity and energy dissipation upon impact. The result of this thesis will focus on a detailed description of the fragmentation process and study several fragmentation mechanisms involved, reproducing many experimental observations of fragment shapes and impact energy, and significantly improve the understanding of the fragmentation process for impact fracture. Spheres shapes were chosen because of their simple body geometry and consequent impact and stress field symmetry. So, the description of materials, sample preparation and tests program conducted for 175 mortar spheres of different diameter built for the current research will be presented to evaluate the survival probability of homogeneous artificial rocks with a known compressive strength dropped from a certain height and to observe the fragmentation process upon impact with a known impacting energy.