Elastic, thermal expansion, plastic and rheological processes - theory and experiment

TL;DR

This paper develops a unified thermodynamic framework to describe elastic, thermal, plastic, and rheological behaviors in rocks, supported by experiments that validate the theoretical predictions and determine rheological coefficients.

Contribution

It introduces a comprehensive continuum thermodynamics model accommodating initial stresses and configurations, integrating multiple deformation phenomena in rocks.

Findings

Experimental validation of the theory with loaded rock samples.

Determination of rheological coefficients from experimental data.

Explanation of temperature changes using the developed thermodynamic model.

Abstract

Rocks are important examples for solid materials where, in various engineering situations, elastic, thermal expansion, rheological/viscoelastic and plastic phenomena each may play a remarkable role. Nonequilibrium continuum thermodynamics provides a consistent way to describe all these aspects in a unified framework. This we present here in a formulation where the kinematic quantities allow arbitrary nonzero initial (e.g., in situ) stresses and such initial configurations which - as a consequence of thermal or remanent stresses - do not satisfy the kinematic compatibility condition. The various characteristic effects accounted by the obtained theory are illustrated via experimental results where loaded solid samples undergo elastic, thermal expansion and plastic deformation and exhibit rheological behaviour. From the experimental data, the rheological coefficients are determined, and the measured temperature changes are also explained by the theory.