Rolling resistance between particles significantly influences the mechanical properties of granular media

yet the underlying mechanisms remain incompletely understood. We conducted several drained triaxial shear tests on granular media using the three-dimensional discrete element method. The simulation results were quantitatively analyzed at macroscopic

microscopic

and mesoscopic scales

followed by a detailed correlation analysis. The study revealed the load transfer and deformation processes in dense granular media

and explored the internal mechanism of the influence of rolling resistance on the mechanical behavior of granular medium. The results show that in the strain hardening stage

the mechanical coordination number decreases

the fabric anisotropy increases

the number of chained particles increases

the force chains become longer

the number of force chains decreases

the average normal contact force increases

the number and volume proportion of small clusters decrease while the number and volume proportion of large clusters increase

and so dilatancy occurs immediately in the specimen after its initial elastic compaction. As the triaxial shear load increases

the contact force between particles in force chains becomes substantial

and the proportion of large clusters surrounding them rises significantly. Consequently

some force chains buckle or collapse

leading to decreased fabric anisotropy

a reduction in the number of chained particles

shortened force chains

and macroscopic strain softening. During the strain hardening stage

large rolling resistance effectively inhibits relative rolling between particles in force chains and reduces the deformability of surrounding large clusters

thereby enhancing force chain stability and increasing the shear strength of the granular medium. During the strain softening stage

rolling resistance prevents timely rearrangement of particles

causing deformation to concentrate in local areas where force chains have bent or collapsed. In these areas

particle rotation increases

leading to the formation of larger clusters. Consequently

the softening and dilatancy of the sample become more pronounced

resulting in the formation of a clear shear band. This study provides deep insights into the complex mechanical behavior of granular media and offers inspiration for the development of multi-scale constitutive theories.