This study investigates the combined effects of particle morphology and the intermediate principal stress ratio b on the multiscale mechanical behavior of granular materials. Four distinct particle morphologies, ranging from nearly spherical to highly irregular, and with or without intrapores, were obtained via X-ray tomography (μCT) scanning and digitally reconstructed. A series of virtual true triaxial tests with varying b values was subsequently conducted on cubic particle assemblies using the level set-discrete element method (LS-DEM). Macroscopically, both the peak and critical stress ratios exhibit a monotonic dependence on b, characterized by an initial rapid decline followed by a gradual reduction before stabilizing. In contrast, the influence of b on dilatancy becomes significant only at relatively high values. Microscopically, the mean coordination number correlates linearly with the friction angle across all morphologies and stress conditions. Analysis of shear-induced anisotropy and particle rotation characteristics reveals that more complex morphologies promote the development of more anisotropic internal structures and restrict the rolling motion of individual particles by locking them in place to enable higher bulk strength. In contrast, increasing b reduces the contact anisotropy and facilitates particle rotation, thereby decreasing the shear resistance. These findings contribute to improved understanding and modeling of granular materials with realistic particle morphologies under complex stress paths.
Li et al. (2026) studied this question.