Monitoring of Thermoelastic Wave Within a Rock Mass Coupling Information from IR Camera and Crack Meters: A 24-Hour Experiment on “Branická Skála” Rock in Prague, Czechia

Racek, Ondřej; Blahůt, Jan; Hartvich, Filip

doi:10.1007/978-3-030-60311-3_3

Cited by 3 publications

(4 citation statements)

References 21 publications

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“…These differences are caused by a combination of the different rock slope aspects and the physical properties of the different rock types. In further research, we plan to use time-lapse thermal camera observation to extend the information to the whole rock slope surface (Racek et al, 2021).…”

Section: Discussionmentioning

confidence: 99%

“…However, the measuring period is still short, with prevailing dry, relatively warm weather. Conversely, there is a visible influence of air and rock mass temperature on block dilatation (Racek et al, 2021), where both diurnal and annual cycles may be identified.…”

Section: Environmental Monitoringmentioning

confidence: 99%

“…However, this may be changed if necessary, e.g. during special experiments such as thermal camera monitoring campaigns (Racek et al, 2021).…”

Section: Dilatation Monitoringmentioning

confidence: 99%

“…The loss of stability, caused by repeated changes in the stress field inside the rock, eventually leads to a rockfall, one of the fastest and most dangerous forms of slope processes (Weber et al, 2017(Weber et al, , 2018Gunzburger et al, 2005). In the alpine environment, rockfalls are increasingly caused by permafrost degradation and frost cracking (Gruber et al, 2004;Ravanel et al, 2017), or temperature-related glacial retreat (Hoelzle et al, 2017). To address the influence of permafrost melting on the rock slope stability, several monitoring systems/campaigns were proposed.…”

Section: Introductionmentioning

confidence: 99%

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Observation of the rock slope thermal regime, coupled with crackmeter stability monitoring: initial results from three different sites in Czechia (central Europe)

Racek

Blahůt

Hartvich

2021

Geosci. Instrum. Method. Data Syst.

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Abstract. This paper describes a newly designed, experimental, and affordable rock slope monitoring system. This system is being used to monitor three rock slopes in Czechia for a period of up to 2 years. The instrumented rock slopes have different lithology (sandstone, limestone, and granite), aspect, and structural and mechanical properties. Induction crackmeters monitor the dynamic of joints, which separate unstable rock blocks from the rock face. This setup works with a repeatability of measurements of 0.05 mm. External destabilising factors (air temperature, precipitation, incoming and outgoing radiation, etc.) are measured by a weather station placed directly within the rock slope. Thermal behaviour in the rock slope surface zone is monitored using a compound temperature probe, placed inside a 3 m deep subhorizontal borehole, which is insulated from external air temperature. Additionally, one thermocouple is placed directly on the rock slope surface. From the time series measured to date (the longest since autumn 2018), we are able to distinguish differences between the annual and diurnal temperature cycles of the monitored sites. From the first data, a greater annual joint dynamic is measured in the case of larger blocks; however, smaller blocks are more responsive to short-term diurnal temperature cycles. Differences in the thermal regime between the sites are also recognisable and are caused mainly by different slope aspect, rock mass thermal conductivity, and colour. These differences will be explained by the statistical analysis of longer time series in the future.

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Section: Discussionmentioning

confidence: 99%

Section: Environmental Monitoringmentioning

confidence: 99%

“…However, this may be changed if necessary, e.g. during special experiments such as thermal camera monitoring campaigns (Racek et al, 2021).…”

Section: Dilatation Monitoringmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Observation of the rock slope thermal regime, coupled with crackmeter stability monitoring: initial results from three different sites in Czechia (central Europe)

Racek

Blahůt

Hartvich

2021

Geosci. Instrum. Method. Data Syst.

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Changes in resonance frequency of rock columns due to thermoelastic effects on a daily scale: observations, modelling and insights to improve monitoring systems

Guillemot

Baillet

Larose

et al. 2022

Geophysical Journal International

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Summary Slope instabilities, including prone-to-fall rock columns, are known to exhibit clear vibrational modes. The resonance frequencies of these modes can be tracked by seismic instrumentation, allowing the rock column's mechanical and structural properties to be monitored, as well as providing precursors of imminent irreversible failures. In previous studies, superficial thermoelastic effects were assumed to drive daily fluctuations in resonance frequencies, but no qualitative or quantitative evidence was provided. The results presented here corroborate this hypothesis and quantify the physical processes involved. We interpreted daily variations of resonance frequencies in the Les Arches study site (Vercors, French Prealps) using a thermo-mechanical finite-element model. Modelled fluctuations of the resonance frequencies over a day closely matched experimental observations, reproducing the daytime frequency increase of around 2%. In addition, our model provides explanation of the various behaviors observed across study sites: the frequency response strongly depends on solar exposure, as well as the timing and intensity of both radiative and convective heat fluxes. We highlight acousto-elastic constants as key parameters of our semi-quantitative model, although they remain poorly constrained here. For future instrumentation, we therefore recommend the deployment of pyranometers on rocky sites to accurately invert these parameters over time, thus allowing rock fracturing to be quantitatively tracked by acousto-elastic monitoring.

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3D Dilatometer Time-Series Analysis for a Better Understanding of the Dynamics of a Giant Slow-Moving Landslide

et al. 2020

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This paper presents a methodological approach to the time-series analysis of movement monitoring data of a large slow-moving landslide. It combines different methods of data manipulation to decrease the subjectivity of a researcher and provides a fully quantitative approach for analyzing large amounts of data. The methodology was applied to 3D dilatometric data acquired from the giant San Andrés Landslide on El Hierro in the Canary Islands in the period from October 2013 to April 2019. The landslide is a creeping volcanic flank collapse showing a decrease of speed of movement during the monitoring period. Despite the fact that clear and unambiguous geological interpretations cannot be made, the analysis is capable of showing correlations of the changes of the movement with increased seismicity and, to some point, with precipitation. We consider this methodology being the first step in automatizing and increasing the objectivity of analysis of slow-moving landslide monitoring data.

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Monitoring of Thermoelastic Wave Within a Rock Mass Coupling Information from IR Camera and Crack Meters: A 24-Hour Experiment on “Branická Skála” Rock in Prague, Czechia

Cited by 3 publications

References 21 publications

Observation of the rock slope thermal regime, coupled with crackmeter stability monitoring: initial results from three different sites in Czechia (central Europe)

Observation of the rock slope thermal regime, coupled with crackmeter stability monitoring: initial results from three different sites in Czechia (central Europe)

Changes in resonance frequency of rock columns due to thermoelastic effects on a daily scale: observations, modelling and insights to improve monitoring systems

3D Dilatometer Time-Series Analysis for a Better Understanding of the Dynamics of a Giant Slow-Moving Landslide

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