Modelling of the induced and inherent anisotropy of sand

非粘性土的应力-应变特性受两种各向异性的显著影响：固有各向异性，即土的初始沉积过程中形成的颗粒骨架的初始组构，以及材料加载过程中产生的诱导各向异性。 土壤的不同形成/放置方法（例如，土地复垦项目的砂浆排放和水下沉积或露天矿中从更高的高度倾倒湿材料）导致材料的不同固有各向异性。实验室测试表明，材料行为对固有和诱导各向异性的依赖性很强，特别是对于土地复垦或露天矿山典型的松散砂。在失效分析或变形预测中，不能忽略这种对各向异性的依赖性。不幸的是，常用的本构模型不考虑织物的影响。本计画的主要目的是扩展一个新的粒状土亚塑性模型，以纳入固有的和诱发的各向异性的影响。为此，该模型采用了两个张量，描述材料的诱导和固有的各向异性。扩展模型将根据对不同方法制备的砂样进行的实验室试验进行修改和校准，即它们具有不同的固有各向异性。随着本构模型的发展，在这个项目中，它将有可能模拟织物或预压效应是显着重要的边值问题。

The stress-strain behavior of non-cohesive soils is significantly influenced by two types of aniso-tropies: the inherent anisotropy, i.e. the initial fabric of the grain skeleton, which is formed during the initial deposition of the soil, and the induced anisotropy which is generated during the loading of the material. Different formation/placement methods of the soil (for example, sand slurry discharge and under water sedimentation for land reclamation projects or wet material dumping from a greater height in open pit mines) lead to different inherent anisotropies in the material. Laboratory tests show a strong dependence of the material behavior on the inherent and induced anisotropy, in particular for loose sand which is typical for land reclamation or open pit mines. This dependence on anisotropy cannot be neglected in failure analysis or deformation prediction. Unfortunately, the constitutive models commonly used do not consider fabric effects. The main objective of this project is to extend a novel hypoplastic model for granular soils in order to incorporate the effects of both the inherent and the induced anisotropy. For this purpose, the model incorporates two tensors, describing the induced and inherent anisotropy of the material. The extended model will be modified and calibrated based on laboratory tests performed on sand specimens prepared by different methods, i.e. they present different inherent anisotropy. With the constitutive model developed in this project, it will be possible to simulate boundary value problems in which fabric or preloading effects are of significant importance.