Impact of Acid Attack on the Shear Behaviour of a Carbonate Rock Joint

• Published in: Rock mechanics and rock engineering 2017-06, Vol.50 (6), p.1439-1451
• Main Authors: Nouailletas, O., Perlot, C., Rivard, P., Ballivy, G., La Borderie, C.
• Format: Article
• Language: English
• Subjects: Acids; Carbon dioxide; Carbon sequestration; Carbonate rocks; Carbonates; Civil Engineering; Computer simulation; Contraction; Dilation; Earth and Environmental Science; Earth Sciences; Geophysics/Geodesy; Joints (timber); Mechanical analysis; Mechanical properties; Mining; Mining engineering; Modelling; Original Paper; Petroleum; Petroleum engineering; Physics; Rocks; Roughness; Shear; Shear tests; Stability; Stability analysis; Stiffness
• ISSN: 0723-2632; 1434-453X
• DOI: 10.1007/s00603-017-1182-6

The mechanical behaviour of structural discontinuities in rock mass is a key element of the stability analysis in civil engineering, petroleum engineering and mining engineering. In this paper, the mechanical analysis is coupled with the acidic attack of a rock joint associated with leakage of CO 2 through a geological fault in the context of carbon sequestration. Experiments were conducted at the laboratory scale to assess the shear behaviour of degraded joint: direct shear tests were performed on rock joints that have been previously immersed into water or into an acidic solution (pH 0.2). The shear behaviour of joints is governed by the roughness of its walls: the parameters Z 2, Z 3, Z 4 and RL characterize the rough surfaces. They are calculated from the scans of joint surfaces after and before immersion. Their comparison pointed out a slight impact of the acidic attack. However, the results of the direct shear tests show significant modifications in the shear behaviour for the degraded joints: the tangential stress peak disappears, the tangential stiffness decreases in the stress/displacement curve, and the contraction increases, the dilation angle decreases in the dilation curve. Acid attack has a greater impact on the mechanical properties of the asperities than their geometric characteristics. The results of this study will be used to improve chemo-mechanical modelling to better simulate with higher accuracy the fault stability in different cases of civil engineering, petroleum engineering and mining engineering.