DEM-based study on the mechanical behaviors of sand-rubber mixture in critical state

This paper presents a numerical method to investigate the critical-state behaviors of the soft-rigid mixture via DEM simulation. First, according to a series of laboratory tests of sand-rubber mixtures, a systematic calibration framework is proposed to acquire the numerical parameters. Then, cubic compression tests are conducted with different rubber contents and confining pressures. The evolution of micro-scale properties, including the internal structure, stress network, and fabric anisotropy, is investigated to reveal the influences of rubber content and confining pressure on the micromechanical behaviors of sand-rubber mixtures. Through the investigation of the macroscopic responses, a unified hypoplasticity constitutive model is established and the relationships between the critical state parameters and rubber content are explored. The results show that the critical state shear strength of sand-rubber mixtures decreases with increasing rubber content and does not correlate with confining pressure. Additionally, the influence of rubber content on shear behaviors of SRMs is highly dependent on confining pressure, e.g., SRMs are more likely to exhibit soft-like behaviors under higher confining pressure. This study lays a foundation for the engineering design of geotechnical structures with an appropriate filling of the sand-rubber mixture. Moreover, this study also paves a viable way for a comprehensive investigation of other soft-rigid mixtures in the critical state.