The behavior of soft soils distributed in coastal areas usually exhibits obvious time‐dependent behavior after loading. To reasonably describe the stress‐strain relationship of soft soils, this paper establishes a viscoelastic‐viscoplastic small‐strain constitutive model based on the component model and the hardening soil model with small‐strain stiffness (HSS model). First, the Perzyna's viscoplastic flow rule and the modified Hardin–Drnevich model are introduced to derive a one‐dimensional incremental Nishihara constitutive equation. Next, the flexibility coefficient matrix is utilized to extend the one‐dimensional model to three‐dimensional conditions. Then, by combining the HSS elastoplastic theory with the component model, the viscoelastic‐viscoplastic small‐strain constitutive model is subsequently established. To implement the proposed model for numerical analysis, the corresponding UMAT subroutine is developed using Fortran. After comparing the results of numerical simulations with those of existing literature, the reliability of the constitutive model and the program written in this paper is verified. Finally, numerical examples are designed to further analyze the effects of small‐strain parameters and viscoelastic‐viscoplastic parameters on the time‐dependent behavior of soft soils.

中文翻译：

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软土小应变刚度和粘弹性-粘塑性特性的数值建模


分布在沿海地区的软土在加载后通常表现出明显的时间依赖性行为。为合理描述软土的应力-应变关系，本文基于组分模型和小应变刚度硬化土模型（HSS 模型），建立了粘弹-粘塑性小应变本构模型。首先，引入 Perzyna 的粘塑性流动规则和改进的 Hardin-Drnevich 模型，推导一维增量 Nishihara 本构方程。接下来，利用柔性系数矩阵将一维模型扩展到三维条件。然后，通过将 HSS 弹塑性理论与组件模型相结合，随后建立了粘弹-粘塑性小应变本构模型。为了实现所提出的数值分析模型，使用 Fortran 开发了相应的 UMAT 子程序。将数值模拟结果与现有文献结果进行比较，验证了本构模型和本文编写的程序的可靠性。最后，设计了数值示例，以进一步分析小应变参数和粘弹性-粘塑性参数对软土瞬态行为的影响。