ON THE INITIATION OF LARGE ROCKSL1DES: PERSPECTIVES FROM A NEW ANALYSIS OF THE VAIONT MOVEMENT RECORD

摘要

The 250 million m'1 Vaiont landslide of 1963 is the largest failure for which monitoring data has been collected in the period in which the failure was initiated. Despite this, and the availability of good geological and geotechnical datasets, considerable uncertainly remains regards the processes occurring within Ihe landslide prior to and during the failure. In this paper, the monitoring data are re-examined to attempt to understand the triggering mechanisms and controls on movement, by plotting I/velocity against time for the 1960 and 1962 movement events, and the 1963 final failure, it is demonstrated that the landslide appears to have undergone a change in deformation mechanism. The 1963 data suggest that the final failure was brittle in nature, but the lack of seismicity effectively rules out large-scale cracking in the limestone. The 1960 and 1962 failures suggest a ductile mechanism. This is used to support the previously proposed initiation mechanism in which deformation of the basal clays in the brittle-ductile transition regime allows movement that is characterised by micro-cracking on the small scale but apparent ductility on the large scale to be superseded by brittle failure when the micro-cracks coalesce.