title: Couple stresses and the fracture of rock.
abstract: An assessment is made here of the role played by the micropolar continuum theory on the cracked Brazilian disc test used for determining rock fracture toughness. By analytically solving the corresponding mixed boundary-value problems and employing singular-perturbation arguments, we provide closed-form expressions for the energy release rate and the corresponding stress-intensity factors for both mode I and mode II loading. These theoretical results are augmented by a set of fracture toughness experiments on both sandstone and marble rocks. It is further shown that the morphology of the fracturing process in our centrally pre-cracked circular samples correlates very well with discrete element simulations.
authors.affiliation: Department of Mathematics, Imperial College London, South Kensington Campus, London SW7 2AZ, UK Schlumberger Gould Research Center, High Cross, Madingley Road, Cambridge, UK c.atkinson@imperial.ac.uk.
authors.forename: Colin
authors.initials: C
authors.lastname: Atkinson
authors.affiliation: Schlumberger Gould Research Center, High Cross, Madingley Road, Cambridge, UK.
authors.forename: Ciprian D
authors.initials: CD
authors.lastname: Coman
authors.affiliation: CEIT and Tecnun (University of Navarra), P. Manuel de Lardizabal 15, 20018 San Sebastian, Spain.
authors.forename: Javier
authors.initials: J
authors.lastname: Aldazabal
keywords: fracture mechanics; micropolar elasticity; singular perturbations; stress analysis