Morphological Evolution of Rock-Slopes and Assessing the Rockfall Activity Index (RAI) Methodology

Abstract

Rockfall poses a significant monetary and life-safety hazard to transportation corridors in mountainous regions. In well-indurated, relatively continuous rock, the orientation and spacing of discontinuities can be quantified to investigate the interaction between distinct rock blocks, and subsequently perform stability analyses. However, in lower-quality, highly discontinuous rock, joint patterns are often too complex to perform traditional stability analyses. Rockfall hazard rating and rock mass classification methodologies have been adopted to provide relative rockfall hazard assessments of slopes in highly jointed rock, but these methods are subjective and have poor spatial resolution. The Rockfall Activity Index (RAI) developed by Dunham et al. (2017) uses high-resolution terrestrial laser scanning-derived point cloud models of rock-slope morphology to provide a higher resolution, quantifiable alternative to traditional hazard rating systems. Using outputs of rockfall detection algorithms at four study sites in Alaska, the efficacy of the RAI system is investigated, and modification to the RAI methodology is proposed to better represent rock-slope mass-wasting processes. Additionally, rockfall detection data is used to understand recession rates and morphological evolution of these rock-slopes.