New risk-consequence rockfall hazard rating system for Missouri highways using digital image analysis

The Missouri Rockfall Hazard Rating System (MORFH RS) is a new scheme for rating rockfall hazards along the roads of the Missouri State highway system. Existing rating systems used in other jurisdictions focus on the risk of failure and ignore the consequence of failure, or they lump the ratings for risk and consequence together. Missouri highway rock cuts tend to have low heights but are typically highly weathered, with special problems from karst and paleokarst. In MORFH RS, risk and consequence factors are given equal weight but isolated from each other. MORFH RS utilizes two phases: 1) identification of the most potentially problematic rock cuts using mobile digital video logging; 2) characterization and prioritization of remediation for the potentially problematic rock cuts identified in phase 1, using MORFH RS. In phase 2 four types of parameters are evaluated: 1) parameters that can be measured on computer scaled video images; 2) parameters which are descriptive, and need field evaluation; 3) parameters which are obtained from MODOT records; 4) conditional parameters which are evaluated under specific conditions. Only those parameters were selected that were deemed meaningful and/or relatively easy to measure or estimate. Parameters were assigned to either a risk or consequence category or both. MORFH RS has been tested on sections of Missouri highways. About 300 rock cuts were evaluated and used to prepare, modify, test, and verify the system. Sensitivity analysis of the system was done by quantifying potential errors in the video measurements and by a rating comparison of 12 MODOT and University of Missouri-Rolla (UMR) personnel on 10 rock cuts along Highway 63.