A thermo-plastic constitutive law for brittle-plastic behavior of rocks at high temperatures

TitleA thermo-plastic constitutive law for brittle-plastic behavior of rocks at high temperatures
Publication TypeJournal Article
Year of Publication1994
AuthorsT Hueckel, A Peano, and R Pellegrini
JournalPure and Applied Geophysics
Volume143
Start Page483
Issue1-3
Pagination483 - 510
Date Published03/1994
Abstract

Mechanical properties of rocks change under the influence of, temperature. Stress at the onset of yielding, ultimate strength, dilatancy, strain hardening and softening, and the confining pressure at brittle-ductile transition are all reduced by the increasing temperature. This study presents a framework of constitutive modeling of thermo-brittle-plastic behavior of rocks which encompasses these changes. The constitutive law is based on a thermo-plasticity theory first proposed for metals by Prager (1958). Two phenomenological mechanisms have been identified as central for the modeling: temperature dependence of the yield locus (thermal softening), and temperature dependence of the strain-hardening function (thermally enhanced ductility). Material parameters for two rocks, Carrara marble and Westerly granite, were determined on the basis of additional hypotheses. These parameters are used in numerical simulations of triaxial tests at different temperatures. The obtained stress-strain curves compare well to the experimental results. The changes with temperature in the stress at the onset of yielding are more accurately reproduced that the evolution of hardening or softening. Suggestions for possible improvements and future research directions are indicated. © 1994 Birkhäuser Verlag.

DOI10.1007/BF00874339
Short TitlePure and Applied Geophysics