A physically-based scale approach to the analysis of the creep process involving mt. granieri (southern italy)

Abstract

In January 1972, a rock slide of more than 2 million m3 moved along the north eastern slope of Mt. Granieri (900 m above sea level), in the Allaro River basin, close to Salincriti village (Calabria region, southern Italy). Subsequent field investigations (geomechanical surveys and laboratory creep tests on rock samples ) validated the initially assumed ongoing “retrogressive” evolution of the phenomenon, which is mobilising a rock mass volume of about one million m3. Data from a remote monitoring system (2 stationary inclinometers at different depths + 1 piezometer) and topographic surveys helped improve the understanding of these slope instabilities. Collected data were used to test a physically-based spatio-temporal approach permitting to scale up laboratory creep test results to the deformational processes of natural slopes. The study assessed whether a time-dependent phenomenon, already at a tertiary-creep stage, was responsible for the deformational processes observed at Mt. Granieri, whose morphological evidence was both reported in the literature about its historical landslides and visible in the topmost portions of the slope. Quantitative analysis of laboratory curves, scaled up to the natural process, made it possible to: i) confine tertiary-creep deformations to the topslope and to the first 300 m from the surface; ii) ascribe tertiary-creep deformations at Mt. Granieri to a highly altered portion of granites and to an underlying poorly altered one, and iii) demonstrate that deformations of the portion of the slope located a few hundreds of metres from the valley floor were dependent on a stationary (secondary-stage) creep process.