A decision analysis framework for the assessment of likely post-failure velocity of translational and compound natural rock slope landslides

An integral component of the assessment of hazard and risk for landslides from large natural rock slopes is the examination of the likely consequences associated with failure. This in turn is inherently related to the post-failure velocity of the slide mass. This paper presents a decision analysis framework for assessment of the post-failure velocity of such slopes. The paper includes discussion of characteristics that influence the post-failure velocity and presents decision trees and supporting matrices to allow assessment of the likely post-failure velocity of translational and internally sheared compound landslides. These represent the most common classes of large rock landslides. The framework is based on data gathered from a large number of landslides from natural rock slopes and incorporates information from a study of excavated rock slopes. These landslides have been studied to determine the factors and characteristics of rock slope failures that influence the post-failure velocity. The framework provides an ability to semiquantitatively assess the uncertainty in prediction of the likely post-failure velocity and identify critical areas of investigation, which would allow for reduction of this uncertainty. The method is expected to be of most use in a quantitative or qualitative risk-based analysis for landslide safety management.