Maximum and minimum void ratios (emax and emin) of granular soils are commonly used as indicators of many engineering properties. However, few methods, apart from laboratory tests, are available to provide a rapid estimation of both emax and emin. In this study, we present a theoretical model to map the densest and the loosest packing configurations of granular soils onto the void space. A corresponding numerical procedure that can predict both emax and emin of granular soils with arbitrary grain size distributions is proposed. The capacity of the proposed method is evaluated by predicting the maximum and minimum void ratios of medium to fine mixed graded sands with different contents of fines. The influence of the grain size distribution, characterized quantitatively by uniformity parameter and the fractal dimension, on emax and emin is discussed using the proposed method. Moreover, application of this method in understanding the controlling mechanism for the void ratio change during grain crushing is presented.
In this study, simple shear tests on breakable polydisperse granular materials were simulated using two-dimensional discrete element method (DEM). A new technique of generating polydisperse DEM samples with a smooth and continuous particle size distribution curve was proposed. A modified breakage criterion was introduced to reflect the contact force anisotropy of particles in the numerical sample. The simulation results showed that during the simple shearing, grain crushing in the sample mainly occurred in the contraction process and decreased gradually when the sample began to dilate. As the shearing proceeded to a larger strain, the grain crushing tended to a stable value. This grain crushing trend was in accordance with the evolution of the average normal contact forces of particles in the sample during shearing. The average normal contact forces of potential breakage particles increased in the contraction process and decreased in the dilatancy process. A decrease in the average normal contact forces of potential breakage particles resulted in the decrease in grain crushing during the later stage of shearing. 相似文献