Influences of particle shape on evolutions of force-chain and micro-macro parameters at critical state for granular materials

Abstract

Abstract Biaxial simulations for samples comprising different particle shapes are used to explore the evolutions of force chains and micro–macro parameters at the critical state, and the particle shape is quantified by the aspect ratio (AR). The AR of the circular, squared, and elongated particles is quantified as 1.00, 0.88, and 0.50, respectively. The use of a new algorithm is proposed to quantify the force chains in granular materials. The force chains in granular materials comprising circular, squared, and elongated particles have similar characteristics. For all three, the distributions of the lengths of the force chains decay exponentially; the chains have a greater average degree (i.e., coordination number) than that of the total sample. Furthermore, the larger degree of a particle, the more likely that it will belong to force chains. In addition, the particle shape has a significant effect on the critical state. The critical state line in the e\u202f−\u202f(p/pa)ξ plane gradually shifts to a lower position on successively considering AR\u202f=\u202f1.00, 0.88, and 0.50, and the critical stress ratio (M) increases as the AR decreases. The evolving curve of the state parameter for the circular particle is always the topmost among those of the three particle shapes, and the curve for the elongated particle is always at the bottom place among three particle shapes. Finally, empirical equations are proposed for establishing the relation between the state parameter and average degree, which are in good agreement with the data of discrete element method.