Experimental and numerical characterization of hydro-mechanical properties of rock fractures : The effect of the sample size on roughness and hydraulic aperture
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A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
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Date
2025-02
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Language
en
Pages
18
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International Journal of Rock Mechanics and Mining Sciences, Volume 186
Abstract
This paper investigated fluid flow in low-stress conditions through rock fractures in Kuru granite measuring 25 cm × 25 cm. Physical aperture and roughness were measured using high-precision photogrammetry. Anisotropy in roughness was observed in two perpendicular directions. Physical aperture under normal stresses was measured, and fracture closure was compared with linear variable displacement transducer (LVDT) measurements, showing good agreement. Hydromechanical tests exhibited nonlinear behavior between fluid pressure gradient and flow rate, following the Forchheimer equation. Applying normal stress resulted in decreased hydraulic aperture and increased nonlinearity of fluid flow. Experimental hydromechanical tests also revealed anisotropy in perpendicular directions, aligning with fracture roughness measurements. Photogrammetric models, aided COMSOL simulations, closely matched the experimental results. Increased stress induced channeled flow and greater tortuosity. Validation of the numerical model allowed simulations on larger fractures. A 2 m × 1 m granite fracture studied scale effects, with the rough surface duplicated and shifted by 350 μm to align with initial aperture measurements of 25 cm × 25 cm samples. Fluid flow simulations assessed subsample sizes (5 cm–100 cm), showing size-dependent variations in roughness, hydraulic aperture, and non-Darcy coefficient, stabilizing beyond 30 cm. This underscores sample size's role in parameter stabilization beyond a 30 cm scale.Description
Publisher Copyright: © 2024 The Author(s)
Keywords
Experimental and numerical tests, Hydraulic aperture, Photogrammetry, Physical aperture, Roughness, Scale effect
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Citation
Torkan, M, Uotinen, L, Baghbanan, A & Rinne, M 2025, ' Experimental and numerical characterization of hydro-mechanical properties of rock fractures : The effect of the sample size on roughness and hydraulic aperture ', International Journal of Rock Mechanics and Mining Sciences, vol. 186, 106009 . https://doi.org/10.1016/j.ijrmms.2024.106009