Thermo-mechanical ratcheting in jointed rock masses

Pastén, Cesar; García, Marcelo V.; Santamarina, J. Carlos

doi:10.1680/geolett.14.00118

Cited by 10 publications

(2 citation statements)

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“…We hypothesize that crack closure may be impeded by loose rock and debris falling into the crack, which prevents crack closure, but has a limited effect on the magnitude of crack opening. This mechanism, sometimes called "thermally induced wedging-ratcheting" (Bakun-Mazor et al, 2013;Pasten et al, 2015;Bakun-Mazor et al, 2020), can drive an increase in fracture opening over time. Thermal contraction on both sides of the crack during cooling causes the crack to widen, allowing for downward movement of infilled debris.…”

Section: Irreversible Crack Openingmentioning

confidence: 99%

Combined ambient vibration and surface displacement measurements for improved progressive failure monitoring at a toppling rock slab in Utah, USA

Jensen,

Moore,

Geimer

et al. 2024

Front. Earth Sci.

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Seismic resonance and surface displacement measurements can be implemented in tandem to improve landslide characterization and progressive failure monitoring. Crack aperture data are frequently used in rock slope stability monitoring and often exhibit recognizable trends prior to failure, such as accelerated crack opening. Alternatively, ambient resonance data offer multiple parameters including modal frequencies, damping, and polarization that can be monitored alongside crack aperture and may respond differently to environmental forcings and complex failure evolution. We analyzed data from continuous ambient vibration monitoring and concomitant crack aperture measurements at the Courthouse Mesa instability, a large toppling sandstone slab in Utah, USA. Three years of data revealed crack aperture increases of 2–4 mm/year with no clearly detectable irreversible changes in modal parameters, including frequency. Annually, frequency and displacement varied by 29% and 19% of the mean, respectively, with average and maximum daily frequency fluctuations of 6.5% and 16%, respectively. These reversible cyclic changes were primarily temperature-driven, but annually, frequency was in-phase with temperature whereas crack aperture lagged temperature changes by ∼37 days. Polarization and damping also varied seasonally but were less strongly correlated with temperature. Conceptual 3D finite element modeling demonstrated consistent frequency decreases associated with crack propagation but variable changes in crack aperture measured at a single point; i.e., crack propagation did not always result in increased crack opening but always generated a resonance frequency decrease. Taken together, our data suggest a possible thermal wedging-ratcheting mechanism at the Courthouse Mesa instability, where annual thermoelastic crack closure is impeded by debris infill but the absence of downward crack propagation during the monitoring period is evidenced by no permanent resonance frequency changes. Our study demonstrates that combined seismic resonance and crack aperture data provide an improved description of rock slope instability behavior, supporting refined characterization and monitoring of changes accompanying progressive failure.

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Section: Irreversible Crack Openingmentioning

confidence: 99%

Combined ambient vibration and surface displacement measurements for improved progressive failure monitoring at a toppling rock slab in Utah, USA

Jensen,

Moore,

Geimer

et al. 2024

Front. Earth Sci.

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“…Primarily, temperature can affect the stress within the fractures, and drive a change of physical parameters such as permeability as a result of thermal fracturing [ 15 ], and/or induce wedging ratcheting [ 16 , 17 ]. The understanding of these comprehensive changes and phenomena is at the base of thermo-mechanical models in geomechanics [ 13 , 18 ], and may allow the prediction of the evolution of the micromorphology at the slope scale.…”

Section: Introductionmentioning

confidence: 99%

Rock Surface Strain In Situ Monitoring Affected by Temperature Changes at the Požáry Field Lab (Czechia)

Racek

Bálek

Loche

et al. 2023

Sensors

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The evaluation of strain in rock masses is crucial information for slope stability studies. For this purpose, a monitoring system for analyzing surface strain using resistivity strain gauges has been tested. Strain is a function of stress, and it is known that stress affects the mechanical properties of geomaterials and can lead to the destabilization of rock slopes. However, stress is difficult to measure in situ. In industrial practice, resistivity strain gauges are used for strain measurement, allowing even small strain changes to be recorded. This setting of dataloggers is usually expensive and there is no accounting for the influence of exogenous factors. Here, the aim of applying resistivity strain gauges in different configurations to measure surface strain in natural conditions, and to determine how the results are affected by factors such as temperature and incoming solar radiation, has been pursued. Subsequently, these factors were mathematically estimated, and a data processing system was created to process the results of each configuration. Finally, the new strategy was evaluated to measure in situ strain by estimating the effect of temperature. The approach highlighted high theoretical accuracy, hence the ability to detect strain variations in field conditions. Therefore, by adjusting for the influence of temperature, it is potentially possible to measure the deformation trend more accurately, while maintaining a lower cost for the sensors.

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