A micromechanical investigation of sand-rubber mixtures using the discrete element method

Mixing soil or sand with tire rubber fibers or buffings is a practical and promising solution to the problem of global scrap tire pollution. However, sand-rubber mixtures exhibit unsatisfactory and complex mechanical properties in engineering applications due to the large deformation of rubber fibers. In this study, a detailed numerical approach to modeling mixtures of sand and rubber fibers via the discrete element method (DEM) was proposed, and the effect of rubber content on the macroscopic and microscopic mechanical behaviors of sand-rubber mixtures was investigated. Furthermore, the reinforcing mechanism by which rubber fibers contribute to the micromechanics of sand-rubber mixtures was explored to determine the optimum rubber content in terms of soil mechanical performance. Comparative analysis of the experimental and numerical results demonstrated the applicability and ability of the proposed DEM model and related parameters for modeling sand-rubber mixtures. Through investigation of the constitutive behaviors of sand-rubber mixtures with various rubber contents under triaxial compression, a rubber content of 20% was found to provide the best shear resistance in the critical state. The micromechanics of sand-rubber mixtures, namely particle kinematics, the interparticle coordination number and rubber fiber deformation, were investigated to demonstrate the specific reinforcing mechanism of rubber fibers with respect to improved soil performance. The resulting data strongly support the identified optimum rubber content for sand-rubber mixtures that will provide a valuable guidance to the relevant engineering applications.