Near infrared spectroscopic measurement of strain in rocks

Butcher, Emily Jane; Gibson, Andy; Benson, Philip; Koor, Nick; Swift, Gareth M.

doi:10.1177/0967033519872540

Cited by 2 publications

(1 citation statement)

References 55 publications

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“…Axial force is monitored using a load cell and displacement (axial and radial) by linear variable differential transducer(s) (LVDT), strain gauge(s) glued onto the sample, optical/laser displacement transducer(s), and/or by a circumferential strain belt. A recent paper also found that near-infrared spectroscopy can be used as a non-contact technique for measuring strain (Butcher et al 2019). Force and displacement (corrected for the displacement of the loading chain) are then converted to axial stress and axial strain using the sample dimensions.…”

Section: Studying Mechanical Behaviour and Failure Mode In The Laboratorymentioning

confidence: 99%

The mechanical behaviour and failure modes of volcanic rocks: a review

2021

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The microstructure and mineralogy of volcanic rocks is varied and complex, and their mechanical behaviour is similarly varied and complex. This review summarises recent developments in our understanding of the mechanical behaviour and failure modes of volcanic rocks. Compiled data show that, although porosity exerts a first-order influence on the uniaxial compressive strength of volcanic rocks, parameters such as the partitioning of the void space (pores and microcracks), pore and crystal size and shape, and alteration also play a role. The presence of water, strain rate, and temperature can also influence uniaxial compressive strength. We also discuss the merits of micromechanical models in understanding the mechanical behaviour of volcanic rocks (which includes a review of the available fracture toughness data). Compiled data show that the effective pressure required for the onset of hydrostatic inelastic compaction in volcanic rocks decreases as a function of increasing porosity, and represents the pressure required for cataclastic pore collapse. Differences between brittle and ductile mechanical behaviour (stress-strain curves and the evolution of porosity and acoustic emission activity) from triaxial deformation experiments are outlined. Brittle behaviour is typically characterised by shear fracture formation, and an increase in porosity and permeability. Ductile deformation can either be distributed (cataclastic pore collapse) or localised (compaction bands) and is characterised by a decrease in porosity and permeability. The available data show that tuffs deform by delocalised cataclasis and extrusive volcanic rocks develop compaction bands (planes of collapsed pores connected by microcracks). Brittle failure envelopes and compactive yield caps for volcanic rocks are compared, highlighting that porosity exerts a first-order control on the stresses required for the brittle-ductile transition and shear-enhanced compaction. However, these data cannot be explained by porosity alone and other microstructural parameters, such as pore size, must also play a role. Compactive yield caps for tuffs are elliptical, similar to data for sedimentary rocks, but are linear for extrusive volcanic rocks. Linear yield caps are considered to be a result of a high pre-existing microcrack density and/or a heterogeneous distribution of porosity. However, it is still unclear, with the available data, why compaction bands develop in some volcanic rocks but not others, which microstructural attributes influence the stresses required for the brittle-ductile transition and shear-enhanced compaction, and why the compactive yield caps of extrusive volcanic rocks are linear. We also review the Young’s modulus, tensile strength, and frictional properties of volcanic rocks. Finally, we review how laboratory data have and can be used to improve our understanding of volcanic systems and highlight directions for future research. A deep understanding of the mechanical behaviour and failure modes of volcanic rock can help refine and develop tools to routinely monitor the hazards posed by active volcanoes.

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Section: Studying Mechanical Behaviour and Failure Mode In The Laboratorymentioning

confidence: 99%

The mechanical behaviour and failure modes of volcanic rocks: a review

2021

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Mount for spectroscopic analysis of samples under sustained tensile stress

Drake,

Farnsworth,

Pinto

et al. 2024

Review of Scientific Instruments

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Spectroscopic methods offer valuable insights into the molecular and structural changes induced by stress, but existing techniques are often unable to perform real-time measurements during deformation. A novel solid open mount design is presented that enables spectroscopic investigations of materials under sustained tensile stress while maintaining crucial alignment of the optical system. The mount design allows for sample movement in response to applied strain while maintaining the position of the sample plane, ensuring consistent and reliable spectroscopic measurements. The effectiveness of the mount design is demonstrated with vibrational sum-frequency generation measurements of an elastomer, cured hydroxyl-terminated polybutadiene, and a plastic, high-density polyethylene, taken before, during, and after tensile deformation. The application of this mount to other spectroscopic techniques is discussed. The ability to collect spectroscopic data during a stress event would provide valuable insights into the behavior of stressed materials.

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Near infrared spectroscopic measurement of strain in rocks

Cited by 2 publications

References 55 publications

The mechanical behaviour and failure modes of volcanic rocks: a review

The mechanical behaviour and failure modes of volcanic rocks: a review

Mount for spectroscopic analysis of samples under sustained tensile stress

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