Laboratory investigation on the mechanical behaviour of Tournemire argillite

This paper presents the results of a laboratory testing program that was designed to investigate the mechanical behaviour of the Tournemire argillite. Eighty rock samples were obtained from boreholes drilled at different angles in the walls and floor of an existing gallery at the Tournemire Underground Research Laboratory (URL), France. The experimental program consists of the measurement of the physical properties of the argillite and its mechanical response to loading during uniaxial tests, triaxial tests with various confining pressures, unconfined and confined cyclic tests, and Brazilian tests. Since the Tournemire argillite is characterized by the presence of closely spaced bedding planes, the rock specimens were loaded in different directions to bedding planes (i.e., loading orientation angle, θ = 0°, 30°, 45°, 60°, and 90°). Acoustic emission data were also recorded to detect the initiation and propagation of micro-cracks during the uniaxial tests. Most of the tests were performed at the natural moisture content of the rock specimens as delivered to CANMET Laboratories in Ottawa, Canada, where the experiments were conducted. The main objective of the testing program is to identify the mechanical properties of the Tournemire argillite. This paper mainly focuses on the description and interpretation of the test results. The development of an elastoplastic-damage model to describe the mechanical behaviour of the Tournemire argillite is the subject of another paper. Key words: deep geological repository, Tournemire argillite, sedimentary rock mass, laboratory tests on sedimentary rock, underground excavation. Cet article presente les resultats d'un programme d'essais en laboratoire concu pour etudier le comportement mecanique de l'argilite de Tournemire. Quatre-vingt echantillons de roche ont ete obtenus a partir de trous de forages fores a differents angles dans les murs et plancher d'une galerie existante au Laboratoire de recherche souterrain de Tournemire en France. Le programme experimental consiste a mesurer les proprietes physiques de l'argilite et ses reponses mecaniques lors d'essais de chargement uniaxial, d'essais triaxiaux avec differentes pressions de confinement, d'essais cycliques non confines et confines, et d'essais bresiliens. Puisque l'argilite de Tournemire est caracterisee par la presence de plans de stratification rapproches, les echantillons rocheux ont ete charge selon differentes directions en relation aux plans de stratification (c'est-adire a des angles d'orientation de charge de 0 = 0°, 30°, 45°, 60° et 90°). Des donnees d'emission acoustique ont aussi ete enregistrees pour detecter l'initiation et la propagation de microfissures durant les essais uniaxiaux. La plupart des essais ont ete realises a la teneur en eau naturelle des echantillons rocheux tel qu'expedies aux laboratoires de CANMET a Ottawa, Canada, ou les essais ont eu lieu. L'objectif principal du programme d'essai est d'identifier les proprietes mecaniques de l'argilite de Tournemire. Cet article presente la description et l'interpretation des resultats experimentaux. Le developpement d'un modele de dommage elasto-plastique pour decrire le comportement mecanique de l'argilite de Tournemire est le sujet d'un autre article. [Traduit par la Redaction] Mots-cles: depot geologique profond, argilite de Tournemire, masse rocheuse sedimentaire, essais en laboratoire sur des roches sedimentaires, excavation souterraine.
Introduction Disposal of radioactive wastes in deep geologic formations is considered internationally as a possible solution for the long-term management of radioactive wastes. Today, many research programs and (or) cooperative [...]