Creep characteristics and unified macro–meso creep model for saturated frozen soil under constant/variable temperature conditions

In permafrost regions, under the interference of climate warming and human activities, the deformation stability of geological engineering with frozen soil as the medium is directly affected, and the typical ones are the creep characteristics under the influence of temperature and stress level. In order to reveal the internal mechanism of such characteristics, this paper carried out the creep tests of saturated frozen soil under constant/variable temperature conditions, and the following meaningful conclusions are drawn: an increase in temperature and deviatoric stress level leads to an increase in the effect of weakening mechanism on the meso-scale, which cause the creep mechanical behavior transition from a stable state to an unsteady state, and eventually reach a failure state; The creep strain and meso-scale broken law caused by temperature history are important features that affect the creep characteristics at subsequent temperature condition. Furthermore, with the breakage mechanics for geological materials and meso-mechanics theories, the strengthening and weakening mechanisms on the meso-scale under the influence of temperature and stress level (deviatoric stress and confining pressure) were defined and quantitatively described in the creep process, and then, an unified macro–meso creep constitutive model was proposed, which includes stress concentration tensor and breakage ratio. Finally, the creep deformation of saturated frozen soil under constant temperature and variable temperature condition was well predicted. The conclusion of the article can be used to evaluate and predict the long-term deformation stability of geological engineering in cold regions.