Abstract:

In order to investigate and predict the internal failure and instability characteristics of gas hydrate coal samples under triaxial action,laboratory triaxial compression tests were first conducted based on the gas hydrate solidification method. Using scanning electron microscope(SEM)images as reference, composite Clump particle templates were constructed to establish biaxial compression models through discrete element method (DEM). The models were featured different particle shapes (irregular and spherical) and saturation levels (40%, 60%, 80%), followed by simulated triaxial compression tests. A comparative analysis was then performed from both macroscopic and mesoscopic perspectives to examine the effects of Clump particles versus spherical particles on the mechanical behavior of gas hydrate-bearing coal. The results demonstrate that the peak strength of specimens increases with hydrate saturation for both particle shapes. The enhancement becomes less pronounced at higher saturation levels. Irregular particle specimens exhibit significantly greater strength than spherical ones, with maximum strength improvement reaching 142.01%. Both saturation and particle shape show limited influence on failure modes. All specimens exhibit bulging failure and X-shaped shear band distribution. Spherical particle specimens display substantially more particle rotations and larger failure zones compared to irregular particles. During loading, irregular particles form stable load-bearing networks through interlocking, supported by their notably higher average coordination number than spherical particles. These findings confirm the superior performance of irregular particle models in characterizing the mechanical behavior of gas hydrate-bearing coal.

Key words: particle shape, gas hydrate-bearing coal, mechanical property, triaxial compression test, flexible boundary