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Do calcite rocks obey the power-law creep equation?

By
Jörg Renner
Jörg Renner
1
Department of Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
2
Institute for Geology, Mineralogy, and Geophysics, Ruhr-University, D-44780 Bochum, Germany
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Brian Evans
Brian Evans
1
Department of Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
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Published:
January 01, 2002

Abstract

The power-law creep equation, ε̇σn exp(−Q/RT), is commonly used to relate strain rate, ε̇, stress, σ, and temperature, T, for thermally activated dislocation creep in rocks. When triaxial deformation experiments on marble and limestone samples are performed at temperatures of 400–1050°C, to strains <0.2, and with strain rates between 10−3 and 10−7s−1, the variations in strength among different rocks at nominally identical conditions are much larger than the experimental uncertainty. During dislocation creep, the strengths of various limestones and marbles decrease with increasing grain size, similar to the Hall-Petch effect in metals. The stress sensitivity of strain rate, n′ = ln ε̇/lnσ, and the temperature sensitivity of strain rate, Q′ = −Rlnε̇/ (1/T), differ greatly for the various calcite aggregates. There is a systematic dependence of n′ and Q′ on stress, grain size, and perhaps, temperature, and there is no interval in stress where n′ is constant. Thus, the steady-state power-law equation is an inadequate description of dislocation creep in calcite rocks. To improve the constitutive law, it may be necessary to include at least one additional state variable that scales with grain size.

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Contents

Geological Society, London, Special Publications

Deformation Mechanisms, Rheology and Tectonics: Current Status and Future Perspectives

S. de Meer
S. de Meer
Utrecht University, The Netherlands
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M. R. Drury
M. R. Drury
Utrecht University, The Netherlands
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J. H. P. de Bresser
J. H. P. de Bresser
Utrecht University, The Netherlands
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G. M. Pennock
G. M. Pennock
Utrecht University, The Netherlands
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Geological Society of London
Volume
200
ISBN electronic:
9781862396081
Publication date:
January 01, 2002

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