The simulation of the viscous behavior of some clays is of high importance in many geotechnical problems. The literature offers a vast amount of constitutive models able to simulate the rate dependence observed on these materials. Although most of thesemodels are calibrated to very similar experimental observations and share similar definitions ofmaterial parameters, some discrepancies of their response have been detected, which are related to their mathematical formulations. In this work, the causes of these discrepancies are carefully studied. To that end, four different model families are analyzed, namely, nonstationary flow surface (NSFS) models, viscoplasticity with overstress function (OVP), viscoplasticity with Norton's power law (NVP), and visco-hypoplasticity (VHP). For the sake of a fair comparison, single constitutive models using the same set of material parameters, and following other requirements, are developed for each model family. Numerical implementations of the four resulting models are performed. Their response at different tests are carefully analyzed through simulation examples and direct examination of their constitutive equations. The set includes some basic tests at isotropic stress states and others as responses envelopes, undrained creep rupture, and an oedometer test with loading, unloading-reloading, creep, and relaxation. The article is concluded with some remarks about the observed discrepancies of these model families.

中文翻译：

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粘性粘土本构模拟不同模型族的比较研究

在许多岩土工程问题中，对某些粘土的粘性行为的模拟非常重要。文献提供了大量能够模拟在这些材料上观察到的速率依赖性的本构模型。尽管这些模型中的大多数都针对非常相似的实验观察进行了校准，并且具有相似的材料参数定义，但已检测到它们的响应存在一些差异，这与它们的数学公式有关。在这项工作中，仔细研究了这些差异的原因。为此，分析了四种不同的模型族，即非平稳流动表面 (NSFS) 模型、具有超应力函数 (OVP) 的粘塑性、具有诺顿幂律 (NVP) 的粘塑性和粘塑性 (VHP)。为了公平比较，为每个模型族开发使用相同材料参数集并遵循其他要求的单一本构模型。执行四个结果模型的数值实现。通过模拟示例和直接检查其本构方程，仔细分析了它们在不同测试中的响应。该套件包括在各向同性应力状态下的一些基本测试，以及其他如响应包络、不排水蠕变断裂以及带有加载、卸载-重新加载、蠕变和松弛的固结仪测试。文章最后对观察到的这些模型系列的差异进行了一些评论。通过模拟示例和直接检查其本构方程，仔细分析了它们在不同测试中的响应。该套件包括在各向同性应力状态下的一些基本测试，以及其他如响应包络、不排水蠕变断裂以及带有加载、卸载-重新加载、蠕变和松弛的固结仪测试。文章最后对观察到的这些模型系列的差异进行了一些评论。通过模拟示例和直接检查其本构方程，仔细分析了它们在不同测试中的响应。该套件包括在各向同性应力状态下的一些基本测试，以及其他如响应包络、不排水蠕变断裂以及带有加载、卸载-重新加载、蠕变和松弛的固结仪测试。文章最后对观察到的这些模型系列的差异进行了一些评论。