Abstract: To examine the mechanical properties of frozen soil under the influence of complex stress paths, a triaxial apparatus is applied to conduct compression tests under different loadings. The corresponding stress states involve generalized triaxial compression stress state, plane strain state and true triaxial stress state. The strength evolution law and deformation of frozen sand in the presence of various stress states are methodically explored. The obtained results reveal that for a constant minor principal stress, the strength of frozen sand and the slope of the stress-strain curve increase in the order of generalized triaxial compressive stress state, plane strain state and true triaxial stress state, respectively. Furthermore, the minor principal stress is capable of enhancing the strength of the frozen soil. The expansion deformation always occurs in the direction of minor principal stress. As the major principal strain grows, the volumetric strain initially shrinks and then expands. For the same test, minor principal stress has a trivial influence on the volumetric strain. Under the same test loading conditions, the smaller the minor principal stress is, the higher the ratio of deviatoric stress to spherical stress is. The failure strength of the sample enhances from the generalize triaxial compression stress state to the plane strain stress state, and then to the true triaxial stress state.

Key words: stress state, strength evolution law, frozen sand, stress-strain curve