Runout analysis and mobility observations for large open pit slope failures

Objectively forecasting the runout of a potential open pit slope failure, in addition to identifying the failure itself, is a critical component of a mine’s risk management plan. Recent losses arising from large open pit slope failures demonstrate shortcomings in current practice. A dataset of 105 pit slope failures was compiled to compare open pit runout trends against established empirical runout relationships for natural landslides. Fahrboschung angle versus volume and Fahrboschung angle versus slope angle relationships provide reasonable runout estimates. Open pit slopes have the advantage of removing the influence of morphological features, vegetation, and liquefiable substrates while controlling the travel path angle and roughness. In such a controlled environment, landslide mobility has a strong sensitivity to slope angle, material properties, and fall height, and is only modestly sensitive to volume. A grouping of highly mobile open pit slope cases involving weathered, saturated, collapsible rock ...