Ambient vibration classification of unstable rock slopes: A systematic approach

Kleinbrod, Ulrike; Burjánek, Jan; Fäh, Donat

doi:10.1016/j.enggeo.2018.12.012

Cited by 50 publications

(54 citation statements)

References 34 publications

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“…However, it is a plausible approximation, considering we assume only weak‐motion excitation in this study, meaning that no irreversible changes of the media are expected. Other potential changes in media (i.e., of the seismic response) are neither expected nor have been observed on the timescales of the ambient vibration experiments (Kleinbrod et al, ). Moreover, the site response at one such fractured slope has been observed to be linear over the measured range of weak input motions spanning two orders of magnitude (Burjánek et al, ), that is the response was the same for both ambient vibrations (0.8 μm peak‐to‐peak displacement) and earthquakes (up to 127 μm).…”

Section: Model Of Media Containing Macroscopic Compliant Fracturesmentioning

confidence: 97%

“…Similar observations have recently been reported for slopes in Italy (Del Gaudio et al, ; Pischiutta et al, ), unstable cliffs in Malta (Iannucci et al, ; Panzera et al, ), and on unstable rock columns (Bottelin, Jongmans, et al, ; Bottelin, Lévy, et al, ; Lévy et al, ; Valentin et al, ). Kleinbrod et al () classified these sites as being volume controlled, since their weak‐motion seismic response seems to be controlled by the entire volume of the unstable rock mass. Steeply dipping compliant fractures, which are common in rock slope instabilities, seem to play a key role in explaining the observed seismic response of volume‐controlled sites.…”

Section: Introductionmentioning

confidence: 99%

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Modeling the Seismic Response of Unstable Rock Mass With Deep Compliant Fractures

2019

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An experimental quantification of the strength and volume of real, heterogeneous, fractured rock masses is crucial when assessing rock slope stability. In order to quantitatively characterize the internal structure of fractured rock slopes, we present three‐dimensional numerical simulations of seismic wave propagation and compare with observations. We introduce a simple, effective model for fractured rock mass, which can easily be applied to simulate weak‐motion seismic wave propagation. The macroscopic compliant fractures cutting the rock mass are modeled as finite‐width zones of reduced elastic parameters characterized by shear and normal stiffness. The widths of such zones are not fixed and can be adjusted to fit the grid step in the numerical method. The proposed rock mass model is applied and tested for the Walkerschmatt site in southwest Switzerland. Synthetic ambient vibrations are generated using a finite‐difference method for the fractured rock mass, shaped by the real terrain geometry, and compared with the measurements. The observed seismic response is satisfactorily reproduced in a broad frequency range (0.5–10 Hz). The synthetized response is primarily controlled by the stiffness, depth, number of fractures, and inertial mass of the fractured rock. The simulated amplification and ground‐motion directionality correspond with the observed levels, unless (1) the simplified cracks reach depths of 200–300 m; and (2) the fracture network is larger with respect to the mapped network. This illustrates the potential of ambient vibration methods in combination with numerical simulations to infer depth, volume, and mechanical characteristics of slope instability.

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Section: Model Of Media Containing Macroscopic Compliant Fracturesmentioning

confidence: 97%

Section: Introductionmentioning

confidence: 99%

Modeling the Seismic Response of Unstable Rock Mass With Deep Compliant Fractures

2019

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“…All of these techniques rely on surface displacements and, in addition, most optical systems depend on meteorological conditions. Therefore, recording ambient vibrations became a promising complementary technique to study rock slope instabilities (e.g., Burjánek et al, 2010;Del Gaudio et al, 2014;Del Gaudio and Wasowski, 2011;Galea et al, 2014;Iannucci et al, 2018;Kleinbrod et al, 2019;Larose et al, 2015;Moore et al, 2011). Ambient vibration measurements might detect changes in the subsurface, which are not directly reflected in surface expressions.…”

Section: Introductionmentioning

confidence: 99%

Monitoring the Preonzo Rock Slope Instability Using Resonance Mode Analysis

Häusler

Michel²,

Burjánek

et al. 2021

JGR Earth Surface

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We monitored an unstable rock slope using frequency domain decomposition modal analysis • We tracked the resonance frequency, mode shapes, and damping ratio of the fundamental and first higher mode over a period of four years • Our study shows seasonal variations of all dynamic parameters and a weak linear relationship between frequency and damping ratio Accepted ArticleThis article has been accepted for publication and undergone full peer review but has not been through the copyediting, typesetting, pagination and proofreading process, which may lead to differences between this version and the Version of Record. Please cite this article as

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“…Polarization analysis and wavefield amplification studies using ambient vibrations acquired at the Randa and Walkerschmatt rock slopes (Burjánek et al, 2010;Burjánek et al, 2012; ©2019. Landslides of this type were classified as volume-controlled sites by Kleinbrod et al (2019). This is an open access article under the terms of the Creative Commons Attribution-NonCommercial-NoDerivs License, which permits use and distribution in any medium, provided the original work is properly cited, the use is non-commercial and no modifications or adaptations are made.…”

Section: Introductionmentioning

confidence: 99%

“…Normal mode phenomena are often observed at slopes characterized by deep fractures that separate the instability in distinct blocks. Landslides of this type were classified as volume‐controlled sites by Kleinbrod et al ().…”

Section: Introductionmentioning

confidence: 99%

Fracture Network Imaging on Rock Slope Instabilities Using Resonance Mode Analysis

Häusler

Michel²,

Burjánek

et al. 2019

Geophysical Research Letters

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We performed modal analysis using frequency domain decomposition of ambient seismic vibration data collected on large rock slope instabilities. This technique enables a robust detection of resonance frequencies and provides the corresponding mode shape vectors. We applied the technique to synthetic and field data sets acquired by seismometer arrays on two rock instabilities in Switzerland. We found that, at the fundamental mode, the entire instability vibrates in‐phase with the dominant mode shape vector oriented perpendicular to dominant fracture systems. At higher frequencies, different compartments of the instability resonate antiphase. Therefore, delineating the zero crossings between the phases allows dominant fractures to be efficiently mapped. Approximately 1 hr of ambient vibration data suffices to apply the method successfully. The method also potentially detects hidden fractures that cannot be observed by geological field mapping. In addition, this approach combines classic amplification and polarization analysis into one technique, simplifying data processing efforts.

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Ambient vibration classification of unstable rock slopes: A systematic approach

Cited by 50 publications

References 34 publications

Modeling the Seismic Response of Unstable Rock Mass With Deep Compliant Fractures

Modeling the Seismic Response of Unstable Rock Mass With Deep Compliant Fractures

Monitoring the Preonzo Rock Slope Instability Using Resonance Mode Analysis

Fracture Network Imaging on Rock Slope Instabilities Using Resonance Mode Analysis

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