Fatigue and damage properties of frozen silty sand samples subjected to cyclic triaxial loading

Cyclic triaxial tests were conducted to explore the influences of dynamic axial loading on the dynamic features and fatigue of frozen silty sand, using an MTS-810 apparatus from Material Testing Systems (MTS). The temperature was −15 °C, and the cyclic axial loads with different amplitudes at 1.0 Hz were applied under confining pressures of 0.6, 1.4, and 6.0 MPa. The cyclic triaxial test results demonstrate that the residual axial strain of the frozen silty sand samples increases gradually during the initial cycles and then increases with increasing number of cycles at a constant speed until failure. The residual volumetric strain contracts during the initial loading cycles and then dilates until failure. Both the residual strain method and the residual volumetric strain method proposed here can be used to describe the degradation process in frozen silty sand samples subjected to cyclic loading. The dynamic axial stiffness of a frozen sample decreases rapidly in the initial cycles and then approaches a stable value with increasing cycle number. The initial damage increases when the stress ratio increases; the larger the stress ratio, the smaller the number of cycles at failure.