The characteristics of a number of rapid rock slope collapses have been presented in published literature. Ten cases of slope collapse are examined in this paper in an attempt to identify those factors that suggest a likelihood of rapid movement and collapse. Five cases are classified as translational slides and the others are classified as compound slides involving internal deformation of the slide mass. The influence of factors such as rupture surface strength and geometry, slide mass characteristics and stress changes are examined. As well as identifying causative factors, the paper discusses some of the pre-collapse deformation behaviour of these rock slides. It is shown that the slides generally exhibited some signs of movement prior to collapse. Brittle behaviour of the compound slides was dependent on slide mass characteristics such as strength and orientation of strata whilst brittle behaviour of the translational slides appears to have been more dependent upon rupture surface characteristics.
Smith and Hungr (1992) suggested that Òthe only feasible, if not exact, method to predict that a rockslide is capable of catastrophic failure is by recognising typical failure mechanisms, and outlining their characteristic behaviour from precedent. They assembled a large database of rockslides and proposed nine classes of detachment mechanism, not all of which were identified as having potentially rapid movement. The term "rapid" is suggested (IUGS, 1995) for describing landslides that have moved or are moving at greater than 1.8m/hour. While this velocity definition may in fact hold true for the cases presented in this paper, the term "rapid" is adopted here in a more general context. No distinct velocity boundary has been used, but rather the term has been adopted here to describe those slides that have progressed to the point of high velocity, sudden disaggregation and collapse.