ROCKFALL HAZARD ANALYSIS USING THE COLORADO ROCKFALL SIMULATION PROGRAM

The Colorado Rockfall Simulation Program (CRSP) was developed to provide a statistical analysis of probable rockfall behavior at any given site and to be used as a tool to study the behavior of rockfalls, to determine the need for rockfall mitigation, and to aid in the design of rockfall mitigation. The basic theory behind CRSP is summarized, and the results of recent program modifications and calibration are discussed. CRSP uses numerical input values assigned to slope and rock properties to model rockfall behavior. The model applies equations of gravitational acceleration and conservation of energy to describe the motion of the rock. Empirically derived functions relating velocity, friction, and material properties are used to model the dynamic interaction of the rock and slope. The statistical variation among rockfalls is modeled by randomly varying the angle at which a rock impacts the slope within limits set by rock size and slope irregularities. The program provides estimates of probable velocity and bounce height at various locations on a slope. Experimental verification and calibration of CRSP was conducted by analyzing videotapes of rocks traveling down a slope. A comparison of rock velocity and bounce height obtained from the tapes with CRSP prediction indicates reasonable agreement. Also, an evalution of the sensitivity of input parameters indicates that slope angle and surface roughness are the most important parameters on steep slopes. Design graphs are developed based on CRSP simulations by using surface roughness and slope angle to estimate rock velocity and bounce height on uniform slopes.