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| Titel |
Investigating tension in the laboratory: Implications for volcanic processes |
| VerfasserIn |
Richard Wall, Yan Lavallée, Jackie Kendrick, Fiona Iddon, Adrian Hornby, Anthony Lamur, Felix von Aulock, Fabian Wadsworth, Christopher Kilburn, John Browning, Philip Meredith |
| Konferenz |
EGU General Assembly 2015
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 17 (2015) |
| Datensatznummer |
250106460
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| Publikation (Nr.) |
 EGU/EGU2015-6133.pdf |
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| Zusammenfassung |
| Tensile fracturing is an important process that occurs at divergent plate boundaries and can
also be observed at convergent plate boundaries, where it accommodates compression. Owing
to the difficulty of simulating tensile loading in the laboratory very few data exist on how
rock fails in this mode and how this process changes with temperature and strain rate. To
address this issue we present the results from a range of experiments that examine direct
tension under controlled conditions.
Experiments have been undertaken using basalt from the base of Eyjafjallajökull volcano
and use a novel methodology of inducing tension through cooling. Initially, samples are
heated above their solidus temperature and are allowed to expand within the apparatus. The
samples are then locked in place and cooled at rates between 0.1 and 10 Ë C.min-1, inducing
tension within the sample. We compare results from these direct tension test with
indirect tension Brazilian tests, using the same rock type, at different temperatures
(between room temperature and 900Ë C) and at a compaction rate of 4 x 10-4
mm.s-1.
From Brazilian tests the tensile strengths of samples are between 10 and 20 MPa, with an
overall increase in strength with increasing temperature. Cooling induced tension
experiments show that direct tensile strength is commonly 50 to 75 % of the strength under
indirect tension conditions and that an increase in cooling rate generally decreases the
strength of the samples. These experiments show a complex stress history during cooling,
from the onset to completion of fracturing. Complementary experiments have also been
undertaken on Seljadur basalt from Iceland, where acoustic emissions and seismic velocities
indicate that the magnitude of thermal cracking is greater during cooling than heating. These
initial results have significant implications for understanding the conditions required for
tensile failure in the field and the controls on the formation of the resulting fracture. |
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