The influence of cryostructure on the creep behavior of ice-rich permafrost

Unconfined constant stress creep (CSC) tests were performed in order to look at the influence of cryostructure on the creep behavior of ice-rich undisturbed permafrost soils and remolded frozen soils within the temperature range from − 1 °C to − 2 °C. Undisturbed ice-rich permafrost soils were sampled from a Pleistocene age yedoma or “ice-complex” permafrost deposit in Interior Alaska. Cryostructure or the pattern of ice inclusions within a frozen soil is a direct indicator of the geologic and cryogenic genesis of permafrost soils. The data indicate that cryostructure influences the creep behavior of permafrost soils. Undisturbed soils with massive cryostructure showed higher induced creep strains and minimum strain rates than the more ice-rich undisturbed soils. Remolded soils with massive cryostructure experienced significantly lower creep strains and lower strain rates than the undisturbed soils. Deformation rates increase rapidly above a threshold stress value for remolded soils. From an engineering viewpoint, use of creep rates from remolded soils is non conservative and under predicts the creep rates of undisturbed soils. The orientation of ice lenses can facilitate motion along the ice lens–soil contact. Similarly, folding of ice lenses may occur, thus inducing anisotropic lateral strains. The ice facies tested indicate that for the temperature and stress range tested, ice creeps at a slower rate than frozen soils.