Abstract: Current numerical simulation studies on water intrusion failure characteristics of mudstone usually update the whole model mesoscale mechanical parameter as the calibration method, which cannot accurately reflect the differences in mechanical responses of specimens under different conditions. To improve accuracy, the simulation method should be updated to reflect the actual failure behavior of mudstone. Relative moisture content (RMC) is introduced to characterize the direct effect of mudstone under different humidification/heating conditions. The general model and the variant stratification (VS) model were constructed, and the mesoscale mechanical parameters were calibrated using the relationship between macroscopic uniaxial compressive strength and surface micromechanical strength to analyze the cementation failure characteristics of each specimen. The results showed that the macroscopic and microscopic strength of the specimens under different humidification/heating conditions varied significantly, and the uniaxial compressive strength weakened with the increase of RMC. The strength of the specimens showed an obvious linear correlation with the thickness of the VS model anisotropy. Compared with the general model, the number and percentage of tension damage cracks and shear damage cracks of the VS model were different, while the damage patterns under different water intrusion conditions were more consistent with the actual test results. Under different conditions, the general model changed significantly for the peak strain energy and cementation energy, while the VS model showed a gentle transition. By analyzing strength variation, damage patterns, and energy release in the simulated specimens, we revealed the mudstone cementation failure characteristics and validated the results for the VS-model specimens.

Key words: mudstone, progressive water intrusion, aspiration/dehydration, variation stratification, PFC modelling