A review of selected unexpected large slope failures

Significant advancements in the application of soil and rock mechanics have been achieved in managing the risk of large-scale slope instability. In practice, however, unexpected slope failures do occur, sometimes with significant safety and economic implications for nearby communities, public infrastructure or the environment. This review focus on large slope failure case studies, considering the slope failure mechanisms and the effectiveness of the controls adopted in managing the geotechnical risk. The role of appropriate data collection and interpretation in underpinning analysis methods is investigated. The impact of levels of uncertainty of input data on different methods of analysis is addressed in the paper. In some instances, the slope failure mechanisms are not understood and can therefore not be incorporated into geotechnical models. It is also found in this review that the safety implications for communities located in the failure path were not initially evident, in some case, resulting in significant loss of life. A thorough understanding of the failure mechanism and triggers is essential for assessing slope stability conditions. In addition, reliable stability monitoring, geological and hydrogeological data are required for determining slope stability conditions. It is also evident from this review that time-dependent behavior is likely to result in shear strength reduction and should be considered for long-term slope stability.