Potential of Rockfall Impacts on Critical Infrastructure During Earthquakes

Abstract

During seismic events, infrastructure in mountainous terrain is often vulnerable to rockfall impacts. This paper presents a probabilistic approach to evaluating the potential of rockfall impacts on an existing hydropower infrastructure under the design ground motions condition. The evaluation was conducted in three steps: (1) identification of potentially unstable rock blocks whose trajectory might reach the infrastructure, (2) seismic stability analysis to evaluate the potential of these rock blocks falling, and (3) rockfall trajectory analysis to evaluate the potential of falling rock blocks reaching the infrastructure. Once relevant rock blocks were identified, pseudo-static rock stability analysis under the design seismic condition using Block Theory was performed. 1,000 random three-dimensional seismic load directions were generated for each rock block. Joint and rock block surface orientations necessary for the stability analysis were identified with LiDAR information. Using the software “RAMMS::ROCKFALL”, rockfall trajectory analysis with 1,000 random initial velocity magnitudes and directions was performed. The peak velocities were estimated from peak ground accelerations selected during the Design Earthquake. Overlaying the results from the stability and trajectory analyses, we identified rock blocks with a potential of failure in case of the design earthquake and, in case of detachment, of impacting the infrastructure due to the applied initial velocities.