SummaryCritical state theory is widely accepted for understanding and interpreting the behavior of granular materials such as sandy soils. Recently, motivated by the development of a multiscale analysis method, this paper presents a discrete element investigation on the critical state behavior of granular materials on two scales level, that is, the macroscale and mesoscale. Loops are taken as the basic mesostructures, and the concept of mesoscale critical state is proposed on terms of the local stress and void ratio. Based on series of numerical simulations with varying densities and confining pressures, the characters of critical state lines (CSLs) for each loop type are analyzed. An analytical relationship of the transition from local to global is then obtained for critical state. Besides, the influence of interparticle friction coefficient on CSL is also discussed on both scales. The prominent observation is that each type of loops achieves its own critical state, from which a unique global CSL can be obtained. The CSLs of different loops exhibit same shapes but move upwards with the increasing order.

No abstract

The evolutions of meso structures of granular materials play important roles during shearing toward the critical state. This study aims to establish an extended analytical model based on a specific upscaling procedure considering the distributions of meso structures in granular materials. A general Gaussian distribution is applied when determining the relationship between meso critical state parameters and order n, and then a quantitative model of macro CSL is developed by taking the discrete case into a continuous function. The quantitative model is then related to interparticle friction μ and contact stiffness k for predicting the macro CSLs for ideal granular assemblies, and the analytical results have good agreement with DEM results. Furthermore, the influence patterns of contact properties on both meso and macro critical states are discussed in detail, which provides a roughly explanation on the variations of critical friction angle with μ.

No abstract

No abstract