Micro-mechanical investigation of non-coaxial plastic flow of granular materials

虽然实验数据已经清楚地表明，土壤行为通常是非同轴（即应力张量和塑性变形率张量的不一致），目前在岩土工程实践中使用的大多数土壤模型仍然是基于塑性势理论，往往预测同轴度。最近的工作表明，忽略非同轴土壤行为将导致不安全的设计在实践中，因此是危险的。为了发展精确的细观力学为基础的，非同轴塑性模型，我们需要进一步了解的细观力学的非同轴流动的颗粒材料。目前的研究表明，土壤结构及其演变是其非共轴行为的主要原因。土壤的固有特性，如颗粒的几何形状和相互作用，也是重要的因素，观察到的程度的非同轴度。然而，目前我们对它们之间的关系和机制还没有详细的了解。因此，本项目的目的是双重的：（a）寻求非同轴土壤行为的物理学的基本理解;和（B），以促进微观力学塑性模型的发展。我们计划实现这一目的，通过使用离散元建模（DEM）的粒状材料在各种应力条件下，涉及主应力旋转。粒状材料的应力旋转试验的实验数据将被用来检查数值离散元模拟的有效性。

Whilst experimental data has clearly demonstrated that soil behaviour is generally non-coaxial (i.e. non-coincidence of stress tensor and plastic rate of deformation tensor), most soil models currently in use in geotechnical practice are still based on the plastic potential theory which often predicts coaxiality. Recent work suggests that ignoring non-coaxial soil behaviour would lead to unsafe design in practice and is therefore dangerous. In order to develop accurate micromechanical-based, non-coaxial plasticity models, we need to further our understanding of the micromechanics of non-coaxial flow of granular materials. Current research suggests that soil fabric and its evolution are the main reason for its non-coaxial behaviour. Soil intrinsic properties, such as particle geometries and interactions, are also important factors to the observed degree of non-coaxiality. At present, however, we have no detailed knowledge about their relationships and mechanisms. The purpose of this present project is therefore two-fold: (a) to seek fundamental understanding of the physics of non-coaxial soil behaviour; and (b) to facilitate the development of micromechanical plasticity models. We plan to achieve this purpose by using discrete element modelling (DEM) of granular materials under various stress conditions involving principal stress rotation. Experimental data on stress rotation tests of granular materials will be used to check the validity of the numerical DEM simulations.