When geophysics met geomechanics: Imaging of geomechanical properties and processes using elastic waves

Hall, Stephen A.

doi:10.1007/978-3-642-03578-4_7

Cited by 3 publications

(1 citation statement)

References 65 publications

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“…Ultrasound techniques have long been used in the laboratory to understand the mechanics of rock deformation and are still flourishing nowadays because they are naturally and directly sensitive to the elastic properties of the material. A significant amount of work has been reported to characterize the damage evolution of rocks by means of conventional ultrasonic methods (Hall, ; Schubnel et al, ), such as ultrasonic pulse velocity or wave attenuation. Such methods are useful to assess major discontinuities associated with significant impedance contrast (or mismatch) in rocks: large cracks, cavities, and fluids.…”

Section: Introductionmentioning

confidence: 99%

Monitoring Local Changes in Granite Rock Under Biaxial Test: A Spatiotemporal Imaging Application With Diffuse Waves

et al. 2018

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Diffuse acoustic or seismic waves are highly sensitive to detect changes of mechanical properties in heterogeneous geological materials. In particular, thanks to acoustoelasticity, we can quantify stress changes by tracking acoustic or seismic relative velocity changes in the material at test. In this paper, we report on a small‐scale laboratory application of an innovative time‐lapse tomography technique named Locadiff to image spatiotemporal mechanical changes on a granite sample under biaxial loading, using diffuse waves at ultrasonic frequencies (300 kHz to 900 kHz). We demonstrate the ability of the method to image reversible stress evolution and deformation process, together with the development of reversible and irreversible localized microdamage in the specimen at an early stage. Using full‐field infrared thermography, we visualize stress‐induced temperature changes and validate stress images obtained from diffuse ultrasound. We demonstrate that the inversion with a good resolution can be achieved with only a limited number of receivers distributed around a single source, all located at the free surface of the specimen. This small‐scale experiment is a proof of concept for frictional earthquake‐like failure (e.g., stick‐slip) research at laboratory scale as well as large‐scale seismic applications, potentially including active fault monitoring.

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Section: Introductionmentioning

confidence: 99%

Monitoring Local Changes in Granite Rock Under Biaxial Test: A Spatiotemporal Imaging Application With Diffuse Waves

et al. 2018

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Precursors to rock failure in the laboratory using ultrasonic monitoring methods

Veltmeijer,

Naderloo,

Barnhoorn

2024

Geomech. Geophys. Geo-energ. Geo-resour.

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Forecasting the occurrence of natural hazards, such as earthquakes or landslides, remain very challenging. These hazards are often caused by stress changes in the subsurface, therefore detecting and monitoring these changes can help the prediction and mitigation. Active ultrasonic transmission experiments were performed on Red Pfaelzer sandstones to investigate the monitoring and forecasting potential of these measurements. The sandstone samples were loaded until failure at different initial confining stress conditions. The forecasting potential to failure of different analysis methods, such as coda wave interferometry or wave attenuation, is investigated and compared. Our results show we can detect the forecast the upcoming failure of the samples from 40 to 70% of its failure point. Small differences between each analysis method are visible, but the trend of the signal is leading and therefore a robust prediction of failure can be made by combining analysis methods. In this paper, we propose a traffic light forecasting system using the precursory signals from ultrasonic monitoring. This system is applicable for monitoring failure at various depths and or stress conditions, for a better prediction of small stress-induced changes in the subsurface and thus mitigation of failure (natural hazards) in the subsurface.

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Timelapse ultrasonic tomography for measuring damage localization in geomechanics laboratory tests

Tudisco

Roux

Hall

et al. 2015

The Journal of the Acoustical Society of America

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Variation of mechanical properties in materials can be detected non-destructively using ultrasonic measurements. In particular, changes in elastic wave velocity can occur due to damage, i.e., micro-cracking and particles debonding. Here the challenge of characterizing damage in geomaterials, i.e., rocks and soils, is addressed. Geomaterials are naturally heterogeneous media in which the deformation can localize, so that few measurements of acoustic velocity across the sample are not sufficient to capture the heterogeneities. Therefore, an ultrasonic tomography procedure has been implemented to map the spatial and temporal variations in propagation velocity, which provides information on the damage process. Moreover, double beamforming has been successfully applied to identify and isolate multiple arrivals that are caused by strong heterogeneities (natural or induced by the deformation process). The applicability of the developed experimental technique to laboratory geomechanics testing is illustrated using data acquired on a sample of natural rock before and after being deformed under triaxial compression. The approach is then validated and extended to time-lapse monitoring using data acquired during plane strain compression of a sample including a well defined layer with different mechanical properties than the matrix.

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When geophysics met geomechanics: Imaging of geomechanical properties and processes using elastic waves

Cited by 3 publications

References 65 publications

Monitoring Local Changes in Granite Rock Under Biaxial Test: A Spatiotemporal Imaging Application With Diffuse Waves

Monitoring Local Changes in Granite Rock Under Biaxial Test: A Spatiotemporal Imaging Application With Diffuse Waves

Precursors to rock failure in the laboratory using ultrasonic monitoring methods

Timelapse ultrasonic tomography for measuring damage localization in geomechanics laboratory tests

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