Robin Fell

Geotechnical characteristics of large slow, very slow, and extremely slow landslides

Based on a study of 45 large slow-moving landslides, it is apparent that for a landslide to travel slowly after failure, the sliding is most likely to be active or reactivated, on a basal rupture surface at or close to residual strength. The likelihood of slow movement after failure is also increased when the inclination of the basal rupture surface is less than the residual friction angle. The slow-moving landslides are all of low rock-mass strength with varying degrees of disaggregation, or they possess soil strength. The influence of lateral margins on landslide restraint is generally small, with landslide movement typically controlled by fluctuations in piezometric pressure. The most commonly observed slow large landslides are mudslides and translational debris–rock slides, followed by particular forms of translational rock slides and internally sheared compound slides. Some mudslides display evidence of short periods of up to moderate velocities.

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 ...