Micromechanical modeling of long-term creep behavior of quasi-brittle rocks considering thermo-mechanical coupling effects

Abstract

A temperature-dependent micromechanical creep–damage constitutive model is proposed within the framework of irreversible thermodynamics and homogenization theory to investigate the long-term thermo-mechanical behavior of quasi-brittle rocks. The model explicitly couples frictional sliding and microcrack propagation as the dominant modes of energy dissipation, where the friction coefficient, critical damage resistance, and damage threshold are expressed as temperature-dependent functions. Subcritical crack growth is incorporated to capture time-dependent damage accumulation and strain development. Model validation is conducted against triaxial thermo-creep experiments on gneissic granite, deep coals, and Beishan granite. The simulations reproduce the complete creep evolution – primary, secondary (steady-state), and tertiary (accelerated) stages – with relatively few parameters. The results clarify the role of creep rate—controlling factors, reveal the mechanisms of damage evolution and strain-rate acceleration under elevated temperatures, and demonstrate the promoting effect of thermal loading on energy dissipation. This unified framework not only advances the understanding of rock creep under coupled thermal–mechanical fields but also provides a theoretical basis for assessing the long-term thermal stability and reliability of deep underground engineering structures.