Monitoring the Preonzo rock slope instability using resonance mode analysis

0542057 - GFÚ 2022 RIV US eng J - Journal Article
Häusler, M. - Michel, C. - Burjánek, Jan - Fäh, D.
Monitoring the Preonzo rock slope instability using resonance mode analysis.
Journal of Geophysical Research-Earth Surface. Roč. 126, č. 4 (2021), č. článku e2020JF005709. ISSN 2169-9003. E-ISSN 2169-9011
Institutional support: RVO:67985530
Keywords : ambient seismic vibrations * damping ratio * frequency domain decomposition * monitoring * resonance frequency * rock slope instability
OECD category: Volcanology
Impact factor: 4.418, year: 2021
Method of publishing: Open access
https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2020JF005709

Reliable monitoring of unstable rock slopes is a prerequisite for successful mitigation of landslide hazards. However, most state-of-the art techniques rely on measuring the local surface displacement in the potential release area. In contrast, recording ambient vibration data allows for analyzing structural dynamic parameters of the unstable slope, such as resonance frequency, polarization of vibration, and energy dissipation. These parameters can be linked to properties of the instability, for example, to rock stiffness and fracture network orientation. We developed a processing method for continuous seismic data based on enhanced frequency domain decomposition modal analysis and applied it to the unstable rock slope Preonzo in Switzerland (similar to 140,000 m(3)). Four years of ambient vibration data recorded at two permanent seismometers on the instability were analyzed, providing the resonance frequency, damping ratio, and normal mode shapes of the fundamental (similar to 3.5 Hz) and the first higher (similar to 4.2 Hz) vibrational mode. We found that modal analysis can be reliably used to monitor the dynamic response of an unstable rock slope. We observed annual changes of all parameters with a damping ratio varying between 6.0% and 9.7% for the fundamental mode. The dynamic parameters appear to be primarily driven by temperature and only secondarily by opening and closing of fractures. No large slope failure was registered during the observation period. However, the data provide a baseline model for ongoing slope monitoring to recognize structural changes before a future collapse. The setup proposed builds a complementary monitoring system to displacement-based surveying.
Permanent Link: http://hdl.handle.net/11104/0319546