In this paper, we outline a constitutive model capable of describing anisotropy and many other features of the behaviour of multiphase granular soils, together with the computational framework that enables its numerical implementation. The constitutive model is formulated within the framework of bounding surface plasticity. It can simulate monotonic and cyclic loading for a wide range of stress and saturation states, it includes enhanced descriptions of wetting and drying processes, of anisotropy and of changing compressibility. These features are captured using a single set of parameters by using a combination of isotropic and kinematic hardening. The model is formulated based on the concept of effective stress for unsaturated states that guarantees smooth transitions between unsaturated and fully saturated states. Furthermore, we present unified formulations for saturated and unsaturated states in which the isotropic hardening law and the critical state line are described in a bi-logarithmic space defined by the logarithms of the mean effective stress and void ratio. Moreover, the constitutive model is coupled with a soil water characteristic model that allows consideration of the hysteretic nature of the saturation degree changes upon wetting/drying reversals. The paper describes the numerical implementation, which includes several smoothing techniques to enhance the constitutive model’s performance in numerical modelling during transitions between kinematic hardening and isotropic hardening and drying/wetting reversals. The numerical implementation also includes automatic error control and sub-stepping techniques, suitable for explicit integration algorithms, that give users additional control over the accuracy and speed of the analysis. Lastly, several examples are provided to demonstrate the range of application of the computational framework.

中文翻译：

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模拟多相颗粒土中应力引起的各向异性

在本文中，我们概述了一个能够描述多相颗粒土壤行为的各向异性和许多其他特征的本构模型，以及能够实现其数值实现的计算框架。本构模型是在边界表面塑性框架内制定的。它可以模拟各种应力和饱和状态的单调和循环载荷，它包括对润湿和干燥过程、各向异性和变化的可压缩性的增强描述。通过使用各向同性硬化和运动硬化的组合，使用一组参数捕获这些特征。该模型是基于不饱和状态的有效应力概念制定的，可保证不饱和状态和完全饱和状态之间的平滑过渡。此外，我们提出了饱和和不饱和状态的统一公式，其中各向同性硬化定律和临界状态线在由平均有效应力和空隙率的对数定义的双对数空间中描述。此外，本构模型与土壤水分特征模型相结合，允许考虑润湿/干燥逆转时饱和度变化的滞后性质。该论文描述了数值实现，其中包括几种平滑技术，以在运动硬化和各向同性硬化以及干燥/润湿反转之间的过渡期间增强本构模型在数值建模中的性能。数值实现还包括自动误差控制和分步技术，适用于显式积分算法，使用户可以额外控制分析的准确性和速度。最后，提供了几个例子来展示计算框架的应用范围。