Assessment of the instability hazard of a granite boulder

This paper aims to assess the instability hazard of a granite boulder. The procedure was first to consider the geological setting and geomorphologic features of the boulder in relation to typical granite landscape forms. Climatic and seismic data were next obtained from different sources, and geomechanical parameters were measured in situ and in the laboratory, with terrestrial laser scanning techniques used to measure shape and volume and to conduct a detailed survey of the boulder. Different analytical approaches were then applied to the calculation of boulder safety factors against sliding and toppling. Since the boulder was considered to be unstable in the worst possible scenario, a particle code approach was used to determine its fall trajectory, calculate the final run out of the block, and assess the risk for houses located at the foot of the slope. Finally, conclusions were drawn regarding the instability hazard, and recommendations were made in regard to definitively stabilizing the granite boulder.