Effects of dry-wet cycles on the cyclic loading characteristics of loess

The typical water sensitivity and dynamic vulnerability of loess are the primary factors contributing to instability to infrastructure on the Loess Plateau. Frequent dry-wet (D-W) cycles, driven by seasonal rainfall, and any other conditions, often result in irreversible damage accumulation in loess. When combined with seismic activity, the disaster-causing process becomes highly complex. Cyclic simple shear tests were conducted to illustrate the cyclic loading response of loess subjected to D-W cycles conditions (D-W cycles times i, lower limit water content w₁) and stress levels (consolidation stress σ_v, and dynamic shear strain amplitude γ_d). The cyclic shear modulus G_d and accumulative axial strain ε_d is significantly influenced by stress levels and D-W cycles conditions. G_d exhibits a two-stage evolution, with the cyclic loading number N corresponding to the inflection point is defined as the critical cyclic loading number N_c, which is inversely proportional to i and w₁. The attenuation of G_d is most significant during the first D-W cycle, with a reduction of 3 %–13.7 %. After i = 8, the attenuation rate of G_d is approximately between 22.66 % and 25.55 %. The ε_d is proportional to the i, w₁, σ_v and γ_d. Based on the monotonicity, boundedness, and memoryless of loess accumulative deformation, a prediction model for accumulative axial strain development is established, incorporating the effects of D-W cycles conditions and stress levels. This model can accurately capture the accumulative deformation of loess during D-W cycles and cyclic loading processes, provide a significant theoretical reference for earthquake disaster prediction in collapsible loess areas.