An elasto-viscoplastic model for frozen-unfrozen clays for combined problems of temperature and load variations

Abstract

Frozen soil’s mechanical behavior is characterized by interactions between solid grains, ice and unfrozen water. It is strongly affected by temperature and ice content, indicating pronounced differences between frozen and unfrozen soils. Rate-sensitive behavior of frozen soil is expected, given the highly rate-dependent behavior of ice. The consequence is reflected in the peculiar features seen in frozen soil’s strength and deformation characteristics under transient temperature and load. To capture these features, an elasto-viscoplastic constitutive model for estimating temperature- and strain rate-dependent behavior of water-saturated clays is presented that is applicable continuously to both frozen and unfrozen states. This model adopts the p’:q plane with a Critical State Line (CSL) that moves with temperature and strain rate while converging to a unique unfrozen CSL, thus it is seamlessly continuous to a conventional elasto-viscoplastic critical state model in unfrozen states. This model is based on an isotach over-stress approach with the cryogenic suction as additional state variable, and is potentially capable of describing varying-load and varying-temperature behaviour seen under combined influence of these two factors.