Non-convex shape effects on the biaxial compression of granular materials composed of monophasic packing and binary mixture

Driven by external compressions or shears, the granular material composed of non-convex shapes often undergoes self-assembly and becomes entangled, resulting in denser packings. In this work, the biaxial compression of monophasic and binary mixture composed of 2D intersecting crosses have been simulated via the discrete element method. As the aspect ratio increases, both the yield strength and elastic modulus initially increase before reaching a peak at w = 0.5. In binary mixtures, an antagonistic effect has been observed in mechanical properties of granular material. The decrease in strength and stiffness in binary mixtures can be attributed to the constraints imposed by multi-point contacts, along with the local order degree, which is particularly unique for non-convex particle packings. Building upon this understanding, we have extended the empirical formula into predicting the mechanical behavior of non-convex binary mixtures. This extension incorporates an additional non-linear term determined by both the shape factor and component fraction.