Analysis of rockfall stop-distance factors with CRSP-3D in volcanic talus

Abstract

The costs associated with rockfall risk are high. Many resources are invested in rock slope maintenance and stabilization, and protection measures to reduce rockfall hazards on transport infrastructures. However, few studies aim to evaluate the relative influence of the different factors (geometrical and material properties) affecting falling rock trajectories and the efficiency (retention capacity) of catchment areas. Numerous factors influence both the characteristics of rockfall motion, and their impact and stop-distance. Ritchie’s empirical research (1963) was the first to identify these characteristics and determine the expected impact distance of rockfalls depending on slope geometry. Later studies showed that Ritchie’s results were not as conservative as previously thought, and also that it was hard to apply his ditches on roadways due to their excessive depth (dangerous for vehicles) and width (expensive construction and maintenance). The Ritchie ditch has therefore been improved by computer simulation programs, and the proposed use of concrete walls or fences at the edge of the road. Optimization of the catchment area geometry requires systematic and quantitative analysis of the effect of each factor on rock stop-distance through application of a simulation model. With this aim, this study applies a CRSP 3D computer simulation model (Colorado DoT, USA) considering 75 different configurations of slope-ditch geometries, 4 types of materials and 9 size and shape combinations of falling rocks. In all we examined 270 different cases for hard rock and 180 for soft rock. A statistical analysis was performed with the simulated rock stop-distances to assess the different variables affecting rockfall motion.