A SIMPLE AND UNIFIED THREE-DIMENSIONAL MODEL TO DESCRIBE VARIOUS CHARACTERISTICS OF SOILS
A SIMPLE AND UNIFIED THREE-DIMENSIONAL MODEL TO DESCRIBE VARIOUS CHARACTERISTICS OF SOILS
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DOI：
10.3208/sandf.51.1129
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发表时间：
2011-12
影响因子：
3.7
通讯作者：
T. Nakai;H. Shahin;M. Kikumoto;H. Kyokawa;Feng Zhang;M. Farias
中科院分区：
文献类型：
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作者：
T. Nakai;H. Shahin;M. Kikumoto;H. Kyokawa;Feng Zhang;M. Farias
摘要 本文提出了一个简单而统一的土壤本构模型，考虑了密度、粘结、时间相关行为等各种影响。首先通过引入代表密度影响的状态变量（第一阶段）来呈现一维应力条件下超固结非结构性土的弹塑性行为。为了描述结构性土的一维应力-应变行为，重点关注密度和粘结作为影响此类土响应的主要因素，因为可以认为土是通过粘结效应形成了比正常固结土更松散的骨架结构（阶段II）。此外，还提出了一种简单的方法，可以考虑其他土壤特性，例如时间和温度依赖性以及非饱和土壤中的吸力影响。实验观察表明，空隙率-应力关系（例如e-ln σ曲线）中的正常固结线（NCL）随着应变率、温度、吸力等的变化而移动（阶段III）。通过模拟正常固结、超固结和天然粘土的一维固结试验，证明了模型在第一阶段和第二阶段的验证。第三阶段模型的适用性不仅通过一维单元试验中粘土随时间行为的模拟得到验证，而且通过里程计试验的土水耦合有限元分析作为边值问题得到验证。通过使用应力不变量而不是一维应力“σ”定义屈服函数并在应力空间中假设适当的流动规则，可以轻松实现从一维模型到三维模型的扩展。一般三维应力条件下的建模细节将在另一篇论文中描述（Nakai et al., 2011）。
ABSTRACT A simple and unified constitutive model for soils, considering various effects such as the influences of density, bonding, time dependent behavior and others, is presented in this paper. The elastoplastic behavior of over consolidated non-structured soils under a one-dimensional stress condition is firstly presented by introducing a state variable that represents the influence of density (stage I). To describe the one-dimensional stress-strain behavior of structured soils, attention is focused on density and bonding as the main factors that affect the response of this type of soil, because it can be considered that soil a skeleton structure which is in a looser state than that of a normally consolidated soil is formed by bonding effects (stage II). Furthermore, a simple method is presented which allows for other soil characteristics to be considered, such as time and temperature dependency, and the effect of suction in unsaturated soils. Experimental observations show that the normally consolidated line (NCL) in the void ratio—stress relation (e.g., e-ln σ curve) shifts depending on the change of strain rate, temperature, suction and others (stage III). The validation of the model at stages I and II is demonstrated by simulating one-dimensional consolidation tests for normally consolidated, over consolidated and natural clays. The applicability of the model at stage III is verified not only by the simulations of time-dependent behavior of clays in one-dimensional element tests but also by the soil-water coupled finite element analysis of oedometer tests as a boundary value problem. The extension from one-dimensional models to three-dimensional models is easily achieved by defining the yield function using stress invariants instead of one-dimensional stress ‘σ’ and by assuming an appropriate flow rule in stress space. The details of the modeling in general three-dimensional stress conditions will be described in another paper (Nakai et al., 2011).