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Pore geometry as a control on rock strength

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journal contribution
posted on 29.11.2016, 15:34 by A. Bubeck, R. J. Walker, D. Healy, M. Dobbs, D. A. Holwell
The strength of rocks in the subsurface is critically important across the geosciences, with implications for fluid flow, mineralisation, seismicity, and the deep biosphere. Most studies of porous rock strength consider the scalar quantity of porosity, in which strength shows a broadly inverse relationship with total porosity, but pore shape is not explicitly defined. Here we use a combination of uniaxial compressive strength measurements of isotropic and anisotropic porous lava samples, and numerical modelling to consider the influence of pore shape on rock strength. Micro computed tomography (CT) shows that pores range from sub-spherical to elongate and flat ellipsoids. Samples that contain flat pores are weaker if compression is applied parallel to the short axis (i.e. across the minimum curvature), compared to compression applied parallel to the long axis (i.e. across the maximum curvature). Numerical models for elliptical pores show that compression applied across the minimum curvature results in relatively broad amplification of stress, compared to compression applied across the maximum curvature. Certain pore shapes may be relatively stable and remain open in the upper crust under a given remote stress field, while others are inherently weak. Quantifying the shape, orientations, and statistical distributions of pores is therefore a critical step in strength testing of rocks.

Funding

This study was funded via RJW's University of Leicester start-up fund, as part of AAB's PhD project.

History

Citation

Earth and Planetary Science Letters 457 (2017) 38–48

Author affiliation

/Organisation/COLLEGE OF SCIENCE AND ENGINEERING/Department of Geology

Version

AM (Accepted Manuscript)

Published in

Earth and Planetary Science Letters 457 (2017) 38–48

Publisher

Elsevier

issn

1385-013X

Acceptance date

28/09/2016

Available date

21/10/2017

Publisher version

http://www.sciencedirect.com/science/article/pii/S0012821X16305301

Language

en

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