A fully probabilistic framework to compute the residual rockfall risk in presence of mitigation measures

Rockfall events are expected to rise throughout the future due to climate change and extreme meteorological events. In the perspective of climate change adaptation, an accurate quantification of the risk is needed, together with a precise assessment of the effectiveness of protective measures eventually installed. All the possible block detachment scenarios together with their occurrence probability should be considered, and a time span should be selected. A fully probabilistic framework to compute the risk in absence and in presence of a protective structure is herein proposed, and a time-integrated reliability-based method, developed by the authors, is applied to define the failure probability of the protective measure. The complete method, in absence and presence of a rockfall barrier, is applied to a study case, and the residual risk in presence of the barrier is quantified. The results show the importance of considering all the possible detachment situations to have reliable results in terms of both risk and effectiveness of the protective measure quantification.