Degrading or thawing permafrost has been identified as being an issue of national importance with respect to its potential for causing severe damages or even loss of lives in densely populated Alpine regions due to climate change (Gruber et al. 2004; Gruber and Haeberli 2007). On this basis, a joint study was initiated by the Safe Mountain Foundation (Fondazione Montagna Sicura, Cormayeur, Italy) and some universities to investigate variations in geotechnical behaviour of the Alpine permafrost caused by changes in temperature. Permafrost is found in the Alpine regions at elevations higher than 2,500 m above sea level, depending on the location and exposure of the slope. Its mechanical features are determined by the combined effect of ice and soil particles. The water content can have an important influence on the shear resistance of the frozen soil: if the water content is low, the ice will not be able to include the soil particles. However, if it is very high, the resistance will be determined above all by the ice itself (Andresland 1987). Temperature is another driving factor that can influence the mechanical behaviour of ice (Fish and Zaretsky 1997). On this basis, this work concentrates on analysing the geotechnical and geophysical behaviour of the dispersed moraine deposits found in Alpine areas, which have been subjected to different climatic conditions due to the effect of high temperatures. The work concentrates on the geotechnical and geophysical characterization of two different glacial deposits present in the Aosta Valley region; the first one generated by the Tsanteleina glacier (Rhêmes Valley, 2,690 m a.s.l.), and the second one surrounding the Blu lake (Ayas Valley, 2,214 m a.s.l.). The characterization was carried out at different scales: laboratory-scale analysis using representative granular materials and field in situ investigations, geotechnical and geophysical testing. The geotechnical measurements were performed using photographic dimension analysis of the deposit, coupled with seismic and electrical surveys. Specimens were collected, remolded, saturated, and kept in a cooler in the laboratory. The specimens were later subjected to laboratory tests to evaluate the geomechanical strength properties of the materials using (mono-axial compressive strength and Young modulus) and geophysical (P and S wave velocities) behaviour of this kind of soils are affected by temperature variations under 0 °C (-35/-5 °C).
|Titolo:||Geotechnical and geophysical characterization of frozen granular material|
|Data di pubblicazione:||2014|
|Appare nelle tipologie:||4.1b Atto convegno Volume|