The significant influence of transverse isotropy on mechanical behaviours of soil has long been recognised, but it is still difficult to capture well under 3D stress conditions. In this study, a method of establishing 3D non-orthogonal elastoplastic (NOEP) constitutive models for transversely isotropic soil (TI-soil) is proposed. The effect of transverse isotropy is considered by extending the characteristic stress with the fabric tensor of TI-soil. The extended characteristic stress can be used to treat the mechanical behaviour of TI-soil from the perspective of isotropic soil. Therefore, a unified strength criterion for TI-soil is developed in the same form as the Drucker–Prager criterion. In order to reflect the non-orthogonality of the plastic flow direction with respect to the yield surface, the non-orthogonal plastic flow rule is adopted, which obviates the tedious work of constructing the plastic potential function or the dilatancy relation. Based on the yield function and hardening parameter expressed in the extended characteristic stress space, specific formulations of the NOEP model for TI-soil can be derived. Comparisons between model predictions and test results show that the developed model can well reflect the effects of transverse isotropy and intermediate principal stress on the strength and deformation behaviour of TI-soil.

人们早已认识到横向各向同性对土壤力学行为的重大影响，但在3D应力条件下仍很难很好地捕获。在这项研究中，提出了一种建立横观各向同性土壤（TI-土）的3D非正交弹塑性（NOEP）本构模型的方法。通过用TI土的织物张量扩展特征应力来考虑横向各向同性的影响。从各向同性土壤的角度来看，扩展的特征应力可用于处理TI土的力学行为。因此，以与Drucker-Prager准则相同的形式开发了TI土的统一强度准则。为了反映塑性流动方向相对于屈服面的非正交性，采用非正交塑性流动规则，这消除了构建可塑性势函数或剪胀关系的繁琐工作。基于在扩展特征应力空间中表示的屈服函数和硬化参数，可以得出TI土的NOEP模型的特定公式。模型预测和试验结果之间的比较表明，所开发的模型可以很好地反映横向各向同性和中间主应力对TI土的强度和变形行为的影响。