Abstract
This study, which presents the results of numerous tests on the sensitivity of mortar permeability under conventional triaxial loading, represents tests carried out over more than a year at various confining pressures under monotonic loading or with loading-unloading cycles. Permeability is measured on a sample, dried prior to the test, by injecting argon—a neutral gas. A description of the experimental method based on applying a permanent flow is given as well as the technique of test study used. In this work, we chose to measure permeability under loading at different levels of deviatoric stress and strain since this corresponds more closely to the real conditions under which the works are used. Preliminary tests showed that the permeability under load was susceptible to early appearance of microcracks and began to increase noticeably towards 75/80% of the stress peak. Further tests were then carried out with loading-unloading cycles for stress levels beyond the stress peak. The authors have shown that permeability inceases very rapidly, starting from this peak. This is irreversible as the measurements taken after unloading the sample prove. The different tests also prove that the damage level is insufficient to allow for a description of variation in permeability, as it clearly depends on the degree to which the microcracks have opened. Such a claim is supported by results where this variation is presented in relation to lateral strain.
Résumé
Ce travail présente le résultats de nombreux essais sur l'étude de la sensibilité de la perméabilité d'un mortier sous chargement triaxial conventionnel, il représente plus d'un an de tests effectués sous chargement monotone ou avec cycles de charge—décharge. La perméabilité est mesurée sur échantillon préalablement séché par injection d'un gaz neutre. La méthodologie expérimentale basée sur l'application d'un régime permanent d'écoulement est détaillée ainsi que la technique de dépouillement des essais. Dans ce travail nous avons fait le choix de mesurer la perméabilité sous chargement, à différents niveaux de déviateur et de déformation car cela correspond plus aux conditions réelles d'utilisation des ouvrages. Quelques tests préliminaires ont montré que la perméabilité sous charge était bien sensible à l'apparition précoce des microfissures et qu'elle commence à augmenter notablement vers 75 à 80% du pic de contrainte. Des tests complémentaires ont ensuite été menés avec des cycles de chargement déchargement pour des niveaux de sollicitation au delà du pic de contraintes. Nous avons montré que la perméabilité augmente très rapidement à partir de ce pic et ceci irréversiblement comme le prouvent les mesures après déchargement de l'échantillon. Ces différents tests prouvent aussi que le niveau d'endommagement est insuffisant pour décrire la variation de perméabilité car elle dépend manifestement du degré d'ouverture des microfissures. Les résultats où cette variation est présentée en fonction de la déformation latérale prouvent cette assertion.
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Meziani, H., Skoczylas, F. An experimental study of the mechanical behaviour of a mortar and of its permeability under deviatoric loading. Mat. Struct. 32, 403–409 (1999). https://doi.org/10.1007/BF02482711
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DOI: https://doi.org/10.1007/BF02482711