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Compaction and Failure in High Porosity Carbonates: Mechanical Data and Microstructural Observations |
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| Authors: | P Baud S Vinciguerra C David A Cavallo E Walker T Reuschlé |
| Institution: | 1. Institut de Physique du Globe de Strasbourg (UMR 7516 CNRS, Université de Strasbourg/EOST), 5 rue René Descartes, 67084, Strasbourg Cedex, France 2. Istituto Nazionale di Geofisica e Vulcanologia, Sezione di Roma1, via di Vigna Murata 605, 00143, Rome, Italy 3. Université de Cergy-Pontoise, 5 mail Gay-Lussac, Neuville-sur-Oise, 95031, Cergy-Pontoise Cedex, France |
| Abstract: | We investigated systematically the micromechanics of compaction in two carbonates of porosity above 30%, Majella grainstone and Saint Maximin limestone. The composition, grain size and pore surface area of these rocks were determined. Hydrostatic compression experiments were performed under dry and wet conditions beyond the onset of grain crushing. A significant water weakening effect was observed in both rocks. A set of conventional triaxial experiments was also performed on both rocks under dry conditions at confining pressures ranging from 3 to 31 MPa. Microstructural observations were carried out on the deformed samples. The mechanical behavior of these high porosity carbonates is dominated by shear-enhanced compaction associated in most cases with strain hardening. Stress-induced cracking and grain crushing are the dominant micromechanisms of deformation in both rocks. In Majella grainstone, compactive shear bands appeared at low confinement, in qualitative agreement with the deformation bands observed in the field. At higher confining pressures, compaction localization was inhibited and homogeneous cataclastic flow developed. In Saint Maximin limestone, compaction localization was observed at all confining pressures. An increasing number of compactive shear bands at various orientations appeared with increasing strain. These new data suggest that compaction localization is important in the mechanical compaction of high porosity carbonates. |
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