Runout estimates and risk-informed decision making for bench scale open pit slope failures

Abstract

Bench scale open pit slope failures are common occurrences in open pit mines and present a hazard to workers near freshly excavated faces. Objectively forecasting the zone of influence of bench scale failures is an important component of the mine’s risk management plan, as they occur more frequently than multi-bench scale landslides and can be more difficult to monitor. This paper presents a dataset of 167 bench scale open pit slope failures and tests runout and bench-width sizing methods to identify appropriate tools to estimate a stand-off distance from a fresh bench face. A length versus fall height and a Fahrböschung angle versus volume relationship calibrated to bench scale open pit slope failures provide reasonable runout estimates and are useful for decision-making when workers are near freshly excavated bench faces. Bench scale open pit failures appear to have a relatively constant fall height/horizontal runout distance (H/L) ratio up to 10 000 m3, after which H/L becomes inversely proportional to volume.