Discrete-Element Simulation of Scaling Effect of Strain Localization in Dense Granular Materials

Abstract

This paper presents a discrete-element method (DEM) study of the scaling effect of strain localization in dense sand. We used disc particles and clump particles to generate specimens for biaxial compression tests, and we adopted a flexible boundary. To investigate the scaling effect, we used a fixed size of specimen composed of different size particles. Numerical simulation reveals that the obtained stress difference and volume strain at a certain strain decrease with R (ratio of specimen width and mean particle size d50). As long as the ratio R is larger than 30, the stress difference, volume strain, peak friction angle, and maximum dilatancy angle approach stable values. The influence of R on the shear strength and volumetric strain of the specimen made of disc particles is greater than the one made of clump particles. With the increase in R, the coordination number and average and maximum contact forces decrease gradually, and the shear band width in dense sand gradually decreases and converges to a constant. The shear band inclination does not reveal obvious variation with R, and the obtained results are close to Roscoe’s formula. When R is large enough (i.e., R ≥ 40), the obtained shear band width keeps a constant, and the influence of particle size on shear band disappears. With the decrease in d50, the ratio of shear band width with d50 gradually decreases; it reaches a stable value when R is large enough.