The role of initial coherence and path materials in the dynamics of three rock avalanche case histories

Abstract

Background: Rock avalanches are flow-like landslides that can travel at extremely rapid velocities and impact surprisingly large areas. The mechanisms that lead to the unexpected mobility of these flows are unknown and debated. Mechanisms proposed in the literature can be broadly classified into those that rely on intrinsic characteristics of the rock avalanche material, and those that rely on extrinsic factors such as path material. In this work a calibration-based numerical model is used to back-analyze three rock avalanche case histories. The results of these back-analyses are then used to infer factors that govern rock avalanche motion Results: Our study has revealed two key insights that must be considered when analyzing rock avalanches. Results from two of the case histories demonstrate the importance of accounting for the initially coherent phase of rock avalanche motion. Additionally, the back-analyzed basal resistance parameters, as well as the best-fit rheology, are different for each case history. This suggests that the governing mechanisms controlling rock avalanche motion are unlikely to be intrinsic. The back-analyzed strength parameters correspond well to those that would be expected by considering the path material that the rock avalanches overran. Conclusion: Our results show that accurate simulation of rock avalanche motion must account for the initially coherent phase of movement, and that the mechanisms governing rock avalanche motion are unlikely to be intrinsic to the failed material. Interaction of rock avalanche debris with path materials is the likely mechanism that governs the motion of many rock avalanches.

Timing, drivers and impacts of the historic Masiere di Vedana rock avalanche (Belluno Dolomites, NE Italy)

“…The IFFI catalogue, the landslide hazard map and the evaluation by Di Giusto focused on the Mt. Peron southern wall and the scree slope, neglecting the well-known deposit of Masiere di Vedana that lies on the southern plain (Abele, 1974;Eisbacher and Clague, 1984;Pellegrini et al, 2006). This is also known as "Rovine di Vedana" (Mazzuoli, 1875;Squinabol, 1902;Montandon, 1933) or "Marocche di Vedana" (Dal Piaz, 1912;Venzo, 1939).…”

Shear‐Rate‐Dependent Behavior of Clayey Bimaterial Interfaces at Landslide Stress Levels

“…Basal sliding can also occur along the soil-rock interface in debris flows, rock slides, and rock avalanches (Chigira et al, 2010;Fan, Xu, Scaringi, Dai, et al, 2017;Hungr et al, 2014;Hu et al, 2015;Xu et al, 2012), although shear localization in this latter typology might not be exclusive (Zhang & McSaveney, 2017). Nevertheless, observations and analyses support a velocity-weakening mechanism-of various possible origins-to explain the catastrophic failure and hypermobility of these types of landslides (e.g., Aaron et al, 2017;Alonso et al, 2016;De Blasio & Crosta, 2015;Handwerger et al, 2016;Hu et al, 2017;Johnson et al, 2016;Lucas et al, 2014;Song et al, 2016;Wu et al, 2017).…”

Transferability of a calibrated numerical model of rock avalanche run‐out: Application to 20 rock avalanches on the Nuussuaq Peninsula, West Greenland

“…This capability was enabled to simulate the early sliding phase of the rock avalanche (Voight and Faust, ; Kelfoun, 2014), which is thought to have initiated as an intact rockfall/slide (Dahl‐Jensen et al, ). This initially coherent stage has greatly improved back‐analyses of similar rock avalanches, with little parameter sensitivity (Aaron and Hungr, ; Aaron et al, ). Measures of entrainment, such as spatial patterns of eroded depths and the downslope lag rate, have not been made for the Paatuut event.…”