Investigation of mechanical properties and elastoplastic numerical calculation model of frozen soil containing ice lenses

As the natural foundation of engineering structures in cold regions, the frozen soil has a vital impact on the deformation of structures during construction and operation stage. The particularity of frozen soil is mainly reflected in its sensitivity to temperature and cryostructure. In this research, a series of uniaxial compressive tests were conducted on four structural types of frozen soil under different temperatures. The test results showed that the axial stress-strain curves of frozen soil containing compaction stage, elastic deformation stage, strain hardening at pre-peak, and failure at post-peak. The unconfined compression strength (UCS) increases as the temperature decreases, the failure strain increases with decreasing temperature when temperature is higher than −3 °C and decreases with decreasing temperature when temperature is lower than −3 °C. Compared with homogeneous frozen soil, the failure surface of heterogeneous frozen soil is formed along the ice-frozen soil interface and the cracks at the tip of ice lenses. Subsequently, the damage variable considering the influence of ice lens and initial defects was deduced based on equivalent strain principle and continuous damage mechanics. An elastoplastic model of heterogeneous frozen soil containing ice lensed is established by using associated flow criterion and Mises strength criterion, and the model was redeveloped in COMSOL Multiphysics. The rationality of the proposed model was verified, and exhibits that the proposed model can capture the mechanical properties of heterogeneous frozen soil.