Structurally and climatically-controlled progressive destabilisation of a multi-unit carbonate rockslide with marly interlayers over two decades (Hornbergl, Tyrol/Austria)
Ettenhuber R, Moser M, Krautblatter M, Paysen-Petersen L (2022)
Publication Type: Journal article
Publication year: 2022
Journal
Book Volume: 173
Pages Range: 311-331
Journal Issue: 2
Abstract
Rockslides in intercalated carbonate rocks are among the most common and hazardous rock slide types in the European Alps and other mountains worldwide. Progressive shear plane development in marly or clayey interlayered lime-stones is an issue of debate, especially since the disastrous 200 million m3 carbonate rockslide in Vajont in 1963. Since in-terlayers are often not persistently developed, the processes controlling the progressive shear plane evolution in carbonate rockslides affecting acceleration and deceleration phases are poorly understood. This paper discusses 20 years of progressive shear plane development in a 10 million m3 multi-unit rockslide with marly interlayers (Hornbergl, Austria). We present a two-decade kinematic record, complemented with field mapping, surface geodetical observations, subsurface geophysical investigations, rock and soil mechanical laboratory testing, a snow-referenced infiltration model, as well as a resulting dis-continuum mechanical model. Monthly tape extensometer measurements (3,300 individual measurements) from 1996 to 2016, mapping and geodetic investigations reveal mean absolute displacement rates of 0.2-14.5 mm/month between multi-ple units of the translational rockslide, often separated by > 20 m deep and meter-wide open fractures. Electrical resistivity tomography (ERT) uncovers the geological and structural setting of the upper 40 m of the rockslide's inner structure. Labo-ratory analysis shows that full (100%) saturation of marly interlayers decreases the cohesion from 65 to 21 kPa in compari-son to 50% saturation, presumably explaining seasonal velocity variations. Correspondingly, infiltration models including snow accumulation and melt appear to control movement patterns in some years after snow melt and after heavy convective rainfalls. Discontinuum mechanical models based on mapping, geophysical reconnaissance and mechanical laboratory test -ing show that the multi-unit rockslide is at the fringe of stability with 50% water saturation in marly interlayers and that strain rates rapidly accelerate with the cohesion loss upon their full water-saturation matching with the described kinematic record. Over multiple years, compression and decompression waves between rockslide units become a first order control for progressive rockslide development. Here we show in a 20-year multi-unit rockslide record, that infiltration after snowmelt and extreme precipitation may control monthly and seasonal patterns of carbonate rockslide defor mation, but compression and decompression waves may become key control on a multiannual time scale for progressive destabilisation.
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Germany (DE)How to cite
APA:
Ettenhuber, R., Moser, M., Krautblatter, M., & Paysen-Petersen, L. (2022). Structurally and climatically-controlled progressive destabilisation of a multi-unit carbonate rockslide with marly interlayers over two decades (Hornbergl, Tyrol/Austria). Zeitschrift der Deutschen Gesellschaft für Geowissenschaften, 173(2), 311-331. https://dx.doi.org/10.1127/zdgg/2022/0302
MLA:
Ettenhuber, Regina, et al. "Structurally and climatically-controlled progressive destabilisation of a multi-unit carbonate rockslide with marly interlayers over two decades (Hornbergl, Tyrol/Austria)." Zeitschrift der Deutschen Gesellschaft für Geowissenschaften 173.2 (2022): 311-331.
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