The aim of this paper is to offer a fresh perspective on the classic concept of critical state (CS) in granular materials by suggesting that CS can be defined through the use of a single proportional strain test. In classic conventional testing, CS manifests itself under constant lateral stress and controlled strain in one given direction whenever continuous shearing is applied without change being induced to material volume. However, a comparison between proportional strain tests and biaxial tests simulated with DEM has clearly shown that the CS line (CSL) characterized by stresses, void ratio and fabric indexes can act as an attractor. The mechanical responses and fabric metrics evolve along dilatant proportional strain loading paths according to similar values after the strain level has become large enough to wipe out the material memory in the homogeneous domains considered in this analysis, i.e., the shear band area in dense samples and the whole area in loose samples. This suggests that the micro-structure of a granular material subjected to any dilatant proportional strain loading paths evolves while preserving its ability to withstand shearing without volume change at any time. Therefore, the CS concept can be generalized to a wide class of loading paths which shows that CS acts as a general attractor irrespective of the loading path considered.

本文的目的是通过建议可以通过使用单个比例应变测试来定义CS，从而为粒状材料中的临界状态（CS）的经典概念提供新的视角。在经典的常规测试中，只要连续施加剪切力而不会引起材料体积的变化，CS就会在给定的方向上承受恒定的侧向应力和受控应变。但是，在比例应变测试和用DEM模拟的双轴测试之间的比较清楚地表明，以应力，空隙率和织物指数为特征的CS线（CSL）可以充当吸引子。在应变水平变得足够大以消除本分析中考虑的均匀域中的材料记忆（即致密样品中的剪切带面积）后，机械响应和织物度量会沿着相似的值沿膨胀比例应变加载路径演变。整个区域都是松散的样品。这表明，经受任何膨胀的比例应变加载路径的粒状材料的微观结构会不断演变，同时保留其随时承受剪切力而体积不会变化的能力。因此，CS概念可以推广到大范围的加载路径，这表明CS充当了一般的吸引子，而与所考虑的加载路径无关。这表明，经受任何膨胀的比例应变加载路径的粒状材料的微观结构会不断演变，同时保留其随时承受剪切力而体积不会变化的能力。因此，CS概念可以推广到大范围的加载路径，这表明CS可以用作一般的吸引子，而与所考虑的加载路径无关。这表明，经受任何膨胀的比例应变加载路径的粒状材料的微观结构会不断演变，同时保留其随时承受剪切力而体积不会变化的能力。因此，CS概念可以推广到大范围的加载路径，这表明CS充当了一般的吸引子，而与所考虑的加载路径无关。