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Article Dans Une Revue International Journal of Rock Mechanics and Mining Sciences Année : 2018

A new approach to quantify the anisotropy of hydromechanical strains in clay-rock at the gallery scale

Résumé

We describe a new method to quantify the anisotropy ratio of hydric strains acquired at the gallery scale and over a period of at least one year. This method was applied in the context of an investigation conducted on a gallery front of the Experimental Station of Tournemire (France), which was subjected to a natural seasonal cycle. Our approach was based primarily on a new algorithm for Digital Image Correlation, known as H-DIC, which can accurately locate desiccation cracks and extract fifteen uncracked blocks with quantified sub-vertical and sub-horizontal strains.The values of the anisotropy ratio of hydric strains (i.e., the ratio of the sub-vertical strains to the sub-horizontal strains, or the ratio of the strains perpendicular to the bedding to those parallel to the bedding) are in the range of [2.84–5.35], with a mean value close to 4.2.The anisotropy ratio for the hydric strains appears to be independent of the natural cycle (i.e., hygrometry) present in the gallery. This observation is supported by a theoretical estimation of this anisotropy ratio, which suggests that the poroelastic parameters of clay rock are insensitive to climatic changes or that theirs evolutions roughly cancel each other out. With regard to geometrical patterns (area, width, height, aspect ratio and orientation) calculated for the uncracked blocks, the anisotropy ratio of the hydric strains does not depend on the area of these uncracked blocks.Moreover, a literature review shows that the values of the anisotropy ratio for the hydric strains determined in this study are significantly larger than those obtained at the laboratory scale on undamaged samples or estimated from a theoretical relationship established in a poroelastic framework. These comparisons strongly suggest that damage to clay rock existing on the gallery front contributes to a significant increase in the anisotropy ratio of the hydric strains.
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Dates et versions

hal-01973587 , version 1 (08-01-2019)

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Stephen Hedan, Valery Valle, Justo Cabrera, Philippe Cosenza. A new approach to quantify the anisotropy of hydromechanical strains in clay-rock at the gallery scale. International Journal of Rock Mechanics and Mining Sciences, 2018, 111, pp.45-53. ⟨10.1016/j.ijrmms.2018.07.004⟩. ⟨hal-01973587⟩
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