The driving force of all nature. Modelling water pressure and its stability consequences on alpine bedrock slopes

Hydrostatic pressure is one of the most important but still not fully understood destabilising factors of bedrock slopes. Water presence has often been recorded in major rock failures like at Piz Cengalo in 2017 but still its quantification and its effective destabilizing role remain unsolved issues...

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Bibliographic Details
Published in:IOP conference series. Earth and environmental science 2021-08, Vol.833 (1), p.12109
Main Authors: Scandroglio, R, Stoll, V, Krautblatter, M
Format: Article
Language:English
Subjects:
Bedrock
Climate change
Destabilization
Forecasting
Hydrostatic pressure
Laboratory tests
Mathematical models
Mechanical properties
Rainfall
Rainstorms
Rockfall
Safety factors
Slope stability
Slopes
Stability analysis
Two dimensional models
Water circulation
Water pressure
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Summary:Hydrostatic pressure is one of the most important but still not fully understood destabilising factors of bedrock slopes. Water presence has often been recorded in major rock failures like at Piz Cengalo in 2017 but still its quantification and its effective destabilizing role remain unsolved issues in rockfall forecasting. Intensification of rainstorms due to climate change will enhance hydrostatic pressures in fractured bedrock, which will likely lead to increase in rockfall activity and connected risks for humans and infrastructures. Here we present a hydro-mechanical stability analysis of the Hochvogel summit (2,592 m AA) in the Northern Calcareous Alps. At this site, an imminent high-magnitude rockfall could destabilise up to 260,000 m 3 and is therefore acutely monitored. Displacement measurements on the summit showed daily acceleration following intense precipitation. With the help of direct investigations and laboratory tests from previous studies, we implemented the Hochvogel SE slope and its mechanical parameters in the 2D Universal Distinct Element Code (UDEC). Our model shows that the presence of water columns of 10 m decreases the factor of safety (FoS) on average by 11 % and can increase the max displacement by up to 70 %. When including the effects of cleft weathering in the model, FoS < 1 can be reached. The friction angle of clefts has a key role in this destabilization process. This study provides key elements for interpreting the mechanical behaviour of this imminent rockfall in connection with hydrostatic pressures, helping to improve hazard forecasting at the Hochvogel and at similar sites.
ISSN:1755-1307
1755-1315
DOI:10.1088/1755-1315/833/1/012109