How to cite:Balme, M.R.; Rocchi, V.; Jones, C.; Sammonds, P.R.; Meredith, P.G. and Boon, S. (2004). Fracture toughness measurements on igneous rocks using a high-pressure, high-temperature rock fracture mechanics cell. Journal of Volcanology and Geothermal Research, ABSTRACTA sound knowledge of mechanical properties of rocks at high temperatures and pressures is essential for modelling volcanological problems such as fracture of lava flows and dike emplacement. In particular, fracture toughness is a scale invariant material property of a rock that describes its resistance to tensile failure. A new fracture mechanics apparatus has been constructed enabling fracture toughness measurements on large (60mm diameter) rock core samples at temperatures up to 750°C and pressures up to 50 MPa. We present a full description of this apparatus and, by plotting fracture resistance as a function of crack length, show that the size of the samples is sufficient for reliable fracture toughness measurements. A series of tests on Icelandic, Vesuvian and Etnean basalts at temperatures from 30-600 o C and confining pressures up to 30 MPa gave fracture toughness values between 1.4 and 3.8 MPam 1/2 . The Icelandic basalt is the strongest material and the Etnean material sampled from the surface crust of a lava flow the weakest. Increasing temperature does not greatly affect the fracture toughness of the Etnean or Vesuvian material but the Icelandic samples showed a marked increase in toughness at around 150 o C, followed by a return to ambient toughness levels. This material also became tougher under moderate confining pressure but the other two materials showed little change in toughness. We describe in terms of fracture mechanics probable causes for the changes in fracture toughness and compare our experimental results with values obtained from dike propagation modelling found in the literature.
L´E sabac è un doppio diploma, con il quale gli alunni del triennio del ciclo di istruzione superiore di primo grado francese e italiano ottengono il rilascio contemporaneo del diploma di maturità e del Baccalauréat. Gli alunni partecipanti al dispositivo hanno così la possibilità di accedere al ciclo di istruzione superiore di secondo grado di entrambi i paesi. Questo percorso di studio è per la Éducation et Sociétés Plurilingues n° 38-juin 2015 Valentina ROCCHI, Gérald SCHLEMMINGER Le travail met en relief les atouts et les faiblesses de l´Esabac, programme d´éducation binationale italo-français, en Toscane. Cette région italienne présente en fait une hétérogénéité par rapport aux établissements scolaires ayant activé ce projet. Dans la partie introductive, le dispositif est introduit à partir des dispositions législatives, qui ont mené à sa création et qui l´ont promu au niveau national. Par la suite, la contribution se plonge dans son étude empirique, constituée par une enquête proposée aux enseignants et aux élèves de classes de terminale de six établissements scolaires toscans. L´analyse se divise ainsi en une étude qualitative impliquant 19 enseignants et en une étude quantitative impliquant 178 élèves. Diese Arbeit möchte ein Gesamtbild der positiven und negativen Aspekte des Esabacs, binationales italienischfranzösisches Abitur, in der Toskana geben. Diese italienische Region wurde aufgrund der Heterogenität, was die Auswahl an dem Programm teilnehmenden Schulen angeht, ausgesucht. Im ersten Teil wird der Esabac im Zusammenhang zu den Rechtsvorschriften, die zu seiner Gründung und Einführung im italienischen Schulsystem gesorgt haben, vorgestellt. Desweiteren widmet sich dieser Beitrag einer empirischen Studie, die aus zwei Befragungen besteht, eine für die 19 Professorinnen und Professoren der sechs ausgewählten Schulen und eine für die 178 Schülerinnen und Schüler. Die entsprechenden Analysen werden jeweils durch einen qualitativen und einen quantitativen Forschungsansatzes durchgeführt.
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