In the present work, a constitutive model for anisotropic clays is proposed and evaluated under monotonic and cyclic loading. To that end, the hypoplastic model for anisotropic clays by Mašín is extended to consider the effects observed on cyclic loading. The extension follows from the intergranular strain anisotropy (ISA) approach by Fuentes and Triantafyllidis. Similar to the intergranular strain (IS) theory by Niemunis and Herle, the ISA extension enhances the model in many aspects, such as the increase of the stiffness and reduction of the plastic strain rate on cyclic loading. Different monotonic and cyclic tests are simulated to evaluate the model's capabilities with the use of samples having vertical and horizontal bedding planes. Simulations obtained with the proposed model and the three-surface kinematic hardening model with transverse isotropic stiffness according to the work of Graham and Houlsby in 1983 (hereafter denoted A3-SKH) are directly compared and analysed. Some additional simulations with the same hypoplastic model extended through the conventional IS theory are also included. The results indicate that a better agreement of the pore pressure accumulation, and some effects emerging from the sample anisotropy, such as ‘inclined’ q–p cycles under undrained conditions, and the dependency of the pore pressure accumulation on the bedding plane direction, are provided by the proposed model. On the other hand, the A3-SKH model estimates with more accuracy the vertical strain accumulation on samples with vertical and horizontal bedding planes.

中文翻译：

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各向异性粘土上单调和循环加载的本构模型

在目前的工作中，提出了一种各向异性粘土的本构模型，并在单调和循环载荷下进行了评估。为此，Mašín 对各向异性粘土的低塑性模型进行了扩展，以考虑对循环载荷观察到的影响。扩展遵循 Fuentes 和 Triantafyllidis 的晶间应变各向异性 (ISA) 方法。类似于 Niemunis 和 Herle 的晶间应变 (IS) 理论，ISA 扩展在许多方面增强了模型，例如在循环加载时增加刚度和降低塑性应变率。模拟不同的单调和循环测试以使用具有垂直和水平层理平面的样本来评估模型的能力。根据 Graham 和 Houlsby 在 1983 年的工作（以下表示为 A3-SKH），直接比较和分析了使用所提出的模型和具有横向各向同性刚度的三表面运动硬化模型获得的模拟。还包括通过传统 IS 理论扩展的相同亚塑性模型的一些附加模拟。结果表明，孔隙压力积累的更好一致性，以及样品各向异性产生的一些影响，例如“倾斜”不排水条件下的q-p循环，以及孔隙压力累积对层理平面方向的依赖性，由所提出的模型提供。另一方面，A3-SKH 模型更准确地估计具有垂直和水平层理平面的样品的垂直应变累积。