In this article, we formulate an anisotropic elastoplastic Cosserat continua model for shear failure in stratified geomaterials. Considering the dip angle between local and global coordinates of a formation, a Cosserat elastic anisotropy constitutive matrix under plane strain condition is derived, and cohesion anisotropy is reflected using a microstructural tensor combined-stress invariant method. A Cosserat continuum finite element model and consistent algorithm are developed to consider the characteristics of elastic anisotropy, strength anisotropy, and strain softening. The simulation of a stratified geomaterial sample under uniaxial compression condition shows that the elastic anisotropy has an evident influence on the deformation pattern. It is also demonstrated that dip angle could significantly impact macroscopic failure modes, uniaxial compressive strength, and macroscopic equivalent elastic modulus. The stability analysis of a layered slope demonstrates that the strength anisotropy has a considerable influence on the overload safety factor of the slope and can be a trigger of the formation of shear bands in such slopes. Furthermore, the dip angle of the structural plane also affects the stability of the stratified slope, which is controlled by both the block and structural surface. By comparing the numerical results of the classical continuum model and the Cosserat continuum model, it is proved that the numerical model considering the elastoplastic anisotropy and strain softening under the Cosserat continuum theory overcomes the ill-posedness of mesh sensitivity and maintains the well-posedness of the strain localization problem. Thus, the proposed model is useful for modeling shear failure in stratified geomaterials.

在本文中，我们为分层岩土材料中的剪切破坏制定了各向异性弹塑性 Cosserat 连续体模型。考虑地层局部坐标与全局坐标之间的倾角，推导出平面应变条件下的Cosserat弹性各向异性本构矩阵，利用微观结构张量组合应力不变法反映黏聚力各向异性。为了考虑弹性各向异性、强度各向异性和应变软化等特性，开发了 Cosserat 连续有限元模型和一致性算法。单轴压缩条件下分层岩土样品的模拟表明，弹性各向异性对变形模式有明显的影响。还表明倾角可以显着影响宏观失效模式，单轴抗压强度和宏观等效弹性模量。层状边坡稳定性分析表明，强度各向异性对边坡超载安全系数有较大影响，可触发层状边坡剪切带的形成。此外，构造面的倾角也影响层状边坡的稳定性，该稳定性受块体和构造面的双重控制。通过比较经典连续介质模型和 Cosserat 连续介质模型的数值结果，证明了 Cosserat 连续介质理论下考虑弹塑性各向异性和应变软化的数值模型克服了网格敏感性的不适定性，保持了应变定位问题。因此，