Abstract:

To investigate the effects of solar irradiation and wetting-drying cycles on the crack evolution of compacted loess and clarify the underlying mechanisms, laboratory tests were conducted using a xenon lamp to simulate solar irradiation under varying irradiance levels, dry densities, and wetting-drying cycles. Surface crack images were periodically captured using a self-developed acquisition system. Crack morphological parameters were extracted using the Particle and Crack Analysis System (PCAS), and micro-pore structures were quantitatively analyzed based on scanning electron microscopy (SEM) images, enabling a systematic macro-micro analysis of crack evolution characteristics. Results indicate that increasing irradiance accelerates crack initiation and increases crack ratio, main crack length, and overall fractal dimension. Within the dry density range of 1.5-1.7 g/cm³, higher dry density effectively reduces crack ratio and connectivity, thereby inhibiting crack propagation. Under wetting-drying cycles, porosity generally increases, pore circularity decreases, and fractal dimension shows an initial increase followed by fluctuations, corresponding well with macroscopic crack evolution. Solar irradiation enhances surface evaporation, intensifies moisture migration and deformation heterogeneity, and promotes the transition from pore structure adjustment to macroscopic crack propagation.

Key words: compacted loess, solar radiation, wetting-drying cycles, crack evolution, microstructure