Structural stability description of undisturbed loess exposed to dry-wet cycles

The typical water sensitivity of loess is the main factor affecting the instability and destruction of infrastructure on the Loess Plateau. Due to frequent dry-wet cycles(D-W cycles) caused by seasonal rainfall, groundwater level fluctuations, and other conditions, loess is often in an irreversible state of cumulative damage. In order to explore the impact of D-W cycles on the structural properties, the D-W cycles test, Scanning electron microscope test, and unconfined compression test were used. The effects of D-W cycles (D-W cycles times N, lower limit water content w₁) on the basic physical properties, mechanical properties, energy storage characteristics, and microstructure of loess were revealed. Results show that the mechanical properties are most significantly affected during the initial D-W cycle. As the w₁ increases, the reduction in strength attributable to the first D-W cycle ranges from 169.65 kPa to 5.64 kPa, representing a decrease of 15.24%. The application of energy conservation principles has elucidated that the energy storage characteristics of loess are compromised by D-W cycles. Based on the D-W durability index D_i and water stability coefficient K_i, the initial structural parameters M is established. Verification of the evolution of initial structural parameters was achieved by correlating basic physical properties, strength parameters, and energy storage characteristics. Structural parameters provide a quantitative description method that can accurately capture the structural evolution of loess during D-W cycles. The research results provide a significant theoretical reference for disaster prediction in collapsible loess areas.