Abstract
AbstractIn this work, the thermo-mechanical stress–strain history of an Alpine slope is analyzed, with particular focus on the historical Cimaganda large landslide (Sondrio Province, Italy), which mobilized an estimated volume of 7.5 mm3 of rock material. Accurate geomorphological and geomechanical characterization involving field surveys and laboratory testing was carried out, leading to the development of a conceptual model of the slope. A thermo-mechanical semi-coupled approach was developed, considering both glacial debuttressing and thermo-mechanical effects due to gradual exposure of the slope to atmospheric conditions and paleo-temperature redistribution resulting from the Last Glacial Maximum deglaciation. A 2D distinct-element numerical approach was adopted, supported by a 2D finite-element analysis to simulate heat diffusion over the Valley cross-section. Modelling results allow to simulate the general evolution of the Cimaganda rock-slope and to highlight the significance of thermal processes in preparing rock-slope instabilities. While the mechanical effect of ice thickness reduction alone brings about moderate rock mass damage, the introduction of temperature couplings results in a substantial increase of damage, representing a significant factor controlling the stress–strain evolution of the slope. Simulated displacement and the development of a deep region of shear strain localization at a depth roughly corresponding to that of the detected Cimaganda sliding surface, allow to highlight the significance of temperature influence in preparing the rock-slope to instability.
Highlights
Rock slope instabilities result from progressive rock mass damage, involving slip propagation along existing discontinuities, failure of intact rock bridges and the creation of new fractures
The factors introduced in the analysis allowed to simulate the general evolution of the Cimaganda rock-slope, which is corroborated by field survey data
Factors leading to a long-term change in the stress state and resisting forces are known as ‘preparatory factors’ (Gunzburger et al 2005) and mainly include climate-driven phenomena such as water pressure changes, long-term glacial evolution, surface temperature variations, chemical and mechanical weathering processes
Summary
Rock slope instabilities result from progressive rock mass damage, involving slip propagation along existing discontinuities, failure of intact rock bridges and the creation of new fractures. Reported cases invoke water pressure changes induced by rainfall events as the main cause of rock mass damage (Preisig et al 2016; Loew et al 2017; Grämiger 2020), especially as ultimate factor for rock-slope failures (Davies 2014; Liu 2021). Another significant trigger for slope instabilities can be represented by earthquake shaking, as discussed in Strom (2015)
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