The damage and fatigue behaviors of frozen soil under combined cyclic compression (tensile)-shear conditions.

• A 3D cyclic stress fields were simulated by frozen hollow cylinder apparatus. • The deformation behaviors were investigated under 3D cyclic stress states. • The damage developing is strongly dependent on the 3D stress characteristics. • A fatigue damage evolution model considering the 3D effect is proposed. The fatigue and damage characteristics of frozen soil under cyclic loading are highly dependent on the three-dimensional (3D) stress state, due to the anisotropic properties of the ground. Measuring and researching the deformation behavior and fatigue failure characteristics of frozen soil under complex 3D cyclic stress states are significant for the stability assessment of frozen soil when it is subjected to earthquakes and vehicular traffic. In this paper, a hollow cylindrical apparatus was used to simulate a cyclic stress state with constant values of principal stress direction angle (α), coefficient of intermediate principal stress(b), and amplitude of the first principal stress under −6℃ conditions. The influences of 3D stress parameters (α and b) on the deformation behavior, damage evolution, and fatigue failure characteristics of frozen silty clay were systematically investigated. The results indicated that the deformation of the samples was dominated by axial strain, when α < 15° and b = 0. Furthermore, as the value b increased, both the accumulated axial strain and accumulated torsional shear strain exhibited a decreasing-then-increasing trend. When 30°≤α ≤ 60°, the deformation feature is primarily dominated by torsional shear direction. With the increase of the value b, the accumulated torsional shear strain increased rapidly, while the axial strain gradually decreases, and then in turn to compressive elongation deformation. The increase of 3D stress parameters leads to a decrease in accumulated torsional shear strain, absolute value of accumulated axial strain, number of cycles, and accumulated torsional shear dissipated energy density at the failure of frozen soil. This indicated that under cyclic stress conditions, the increase of 3D stress characteristic parameters accelerates the damage evolution and fatigue failure process of frozen soil samples. Essentially, the increase of 3D stress parameters accelerates the damage of soil particle and ice lens structures in horizontally layered and the growth of micro-crack of frozen soil, thereby reducing the transverse shear resistance of frozen soil samples. [ABSTRACT FROM AUTHOR]