有机质固相变形对各向异性泥炭土力学特性的影响机制与弹黏塑性模型

泥炭土具有明显异于且差于一般软土的工程性质，常常被视为“问题土”。项目以泥炭土工程问题日益突出而其机理认知尚不充分的现状为背景，从泥炭土低不排水抗剪强度与高有效内摩擦角异常组合的试验现象出发，以泥炭土中有机质固相可压缩这一常被忽视的重要特征为切入点，提出量测颗粒固相压缩变形的试验方法，查明有机质固相变形特性，建立泥炭土有效应力表征公式；随后，针对不同有机质含量和分解度的泥炭土，开展多种应力路径原位与室内力学响应试验，明晰有机质固相变形对泥炭土力学特性的影响机制，提出泥炭土有效应力抗剪强度指标辨识确定方法，揭示泥炭土各向异性与时效特征，并查明有机质含量和分解度的影响效应；最后，基于临界状态理论和超应力黏塑性理论，结合泥炭土有效应力表征公式，耦合各向异性与时效特征，建立泥炭土本构模型，并对模型数值化，为我国泥炭土地基基础设计、长期沉降预测以及综合处理提供科学依据。

Peaty soils are often viewed as “problematic soil” because their engineering properties are inferior to those of other soft soils. Although the engineering problems have become increasingly prominent, the relevant mechanism research is still insufficient. Inspired by the abnormal combination of low undrained shear strength and high effective internal friction angle of peaty soils, the compressibility of organic matter that is often overlooked will be studied firstly in this study. An experimental method for measuring the deformation of organic matter will be proposed. By identifying the deformation behaviour, a formulation of the effective stress for the peaty soils will be obtained. Then, a series of stress-path tests, including in situ and laboratory tests, for the peaty soils with different organic matter content and decomposition will be carried out. Accordingly, the effect of deformation of organic matter on the deformation and strength properties of peaty soils will be discussed. A method for determining the effective stress shear strength index will be presented. Furthermore, the anisotropy and time-dependency of peaty soils as well as the effect of organic matter content and decomposition will be investigated. Finally, utilizing the proposed formulation of the effective stress, an anisotropic elasto-viscoplastic constitutive model for the peaty soil will be proposed based on the critical state theory and the overstress viscoplastic theory, in which the influences of anisotropy and time-dependent behaviour are considered. Also, the proposed model will be implemented in finite-element formulations. The resulting findings of this study are helpful to offer scientific basis for the foundation design, settlement prediction and foundation treatment for the peaty soils.