The micro-mechanical behaviour of sand-rubber mixtures under shear: A numerical study based on X-ray micro-tomography

A CT image-based discrete element model (DEM) incorporating the realistic particle morphology of sand grains was developed to investigate the micro-mechanical behaviours of sand-rubber mixtures (SRMs) under triaxial compression. The model was validated by comparing the numerically simulated macro-and microscale me-chanical behaviour of SRMs with the experimental results acquired in triaxial testing with in-situ mu CT scanning. SRMs with irregularly shaped grains have a higher degree of heterogeneous distribution of contact force chains than those with spherical grains. Moreover, rubber content and particle shape have a significant influence on the 'most active phase', namely, the time-period during which the maximum number of contacts emerged to participate in the stress-transmission, of different types of contacts. The 'most active phase' of sand-sand contacts appeared earlier than that of sand-rubber contacts. SRMs with a lower rubber content were more likely to have an earlier 'most active phase' for each type of contact. The sequence of the 'most active phase' for the sand-rubber contacts and rubber-rubber contacts appeared during shear was affected by the particle shape of the SRM specimens. The results highlight the important role of rubber content and particle shape in the stress-transmission behaviour of SRMs.