A critical-state constitutive model for rate-dependent deformation of permafrost

ABSTRACT: In permafrost regions, the long-term serviceability of infrastructure founded on highly plastic foundation is adversely affected by slow-rate, time-dependent deformations (i.e., viscous or creep behavior) of permafrost subject to climate change. Investigating such deformations in a Thermo-Hydro-Mechanical (THM) framework requires a coupled non-isothermal strain-rate geomechanical constitutive model. Long-term deformations of geomaterials are commonly estimated by a combination of instant and delayed components of deformations. The instant component is associated with largely reversible (elastic) deformations of the soil while the delayed component includes non-recoverable (plastic), time-dependent and simultaneous thermo-viscoplastic reorganization of the inter-particle microstructure. Based on this approach, a Thermal Elastic-ViscoPlastic (TEVP) constitutive model is formulated in accordance with the Critical State Soil Mechanics (CSSM) framework to investigate the creep behavior of permafrost. The model predictions fit reasonably well the experimental data available in the literature.