Quantitative hazard analysis and mitigation measures of rockfall in a high-frequency rockfall region

The runout behavior of rockfall is mostly determined by the terrain and its mechanical parameters. The two factors can be significantly changed in a short period of time due to rockfall deposits in high-frequency rockfall regions. In this paper, a self-evolution process of rockfall from the Hongshiyan post-earthquake rock slope is observed and analyzed. This self-evolution process of the rockfall is the consequence of the re-occurrences of a large number of rockfall events in a short period of time, which lead to an increase in the elevation, slope angle, and hardness of the terrain, and aggravate further the severity of subsequent rockfall disasters. In order to analyze the self-evolution process, numerical simulations based on a probabilistic model were carried out on eight different conditions to analyze the interaction between the rockfall and different ground surface. The corresponding rockfall hazard was then analyzed according to a quantitative assessment method. The statistics of the average class (AC) and mitigation index (MI) of the rockfall were proposed to quantify the rockfall characteristics in different conditions. The effectiveness of structural and non-structural rockfall protection measures in high-frequency rockfall areas was discussed. An interim non-structural measure that addresses the self-evolution of rockfall is proposed to improve the mitigation efficiency, which can also reduce the maintenance cost.