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Fracture toughness measurements on igneous rocks using a high-pressure, high-temperature rock fracture mechanics cell

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, 132(2-3) pp. 159–172.

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A 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 (60 mm 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 to 600–C and confining pressures up to 30 MPa gave fracture toughness values between 1.4 and 3.8 MPa m1=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–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.

Item Type: Journal Item
ISSN: 0377-0273
Extra Information: (1) Some of the symbols may not have transferred correctly into this bibliographic record and/or abstract.
(2) The final version was published in the Journal of Volcanology and Geothermal Research, vol 132, no 2-3, pp 159-172. The attached PDF version is post-peer-review but may differ slightly to the final published version.
Academic Unit/School: Faculty of Science, Technology, Engineering and Mathematics (STEM) > Physical Sciences
Faculty of Science, Technology, Engineering and Mathematics (STEM)
Item ID: 5495
Depositing User: Matthew Balme
Date Deposited: 05 Oct 2006
Last Modified: 01 May 2019 16:55
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