长期循环荷载作用下泥炭土地基由于疏松的结构形态会产生显著的工后附加沉降，而目前对其变形特性的研究尚未系统展开，累积变形发展机理尚不明确。本项目针对泥炭土富含有机质且有机质对力学性能影响显著这一特征，以不同有机质含量泥炭土为研究对象，开展考虑不同试验控制条件组合的不排水循环三轴试验，明确累积变形发展规律及有机质对其影响效应，建立归一化的累积塑性应变计算模型；从微观角度出发，查明泥炭土微观结构演变规律，耦合分析宏观试验结果，构建微观结构演化方程，揭示累积变形发展机理；在临界状态理论和边界面模型理论框架内，考虑有机质影响以及微观结构演化特征，建立泥炭土弹塑性边界面动力本构模型，对模型程序化以及开发高效的数值算法，结合有限元分析泥炭土地基在不同循环荷载作用下产生的累积变形发展规律。研究成果可为泥炭土地基上已建工程的工后沉降合理预测、在建和拟建工程采取有效措施控制和减小长期沉降提供科学依据。

Under the long-term cyclic loading, the foundation constructed on peat soil emerges a considerable additional post-construction settlement due to the loose structure of peat. However, the study on deformation characteristics of peat soil is still not systematically developed and the deformation mechanism is also still indeterminacy. Considering that peat soil is rich in organic matter and its effect on mechanical properties is significantly, this study will conduct undrained cyclic triaxial tests against peat soil samples with different organic contents, where the combination of different control conditions are designed. And the development law of accumulative deformation and the effect of organic matter will be determined, and a normalized calculation model of cumulative plastic strain will be proposed. Then, from the micro perspective, the evolution process of microstructure of peat soil will be understand combining with the macro mechanical tests, and evolution equation of microstructure will be established, also the accumulative deformation mechanism will be essentially revealed. On this basis, taking into account of the effect of organic matter and evolution characteristics of microstructure, elasto-plastic boundary surface model for peat soil will be built up relying on the critical state theory and boundary surface model theory. In addition, the constitutive model will be compiled and an efficient numerical algorithm will also be provide. Finally, deformation characteristics of foundations constructed on peat soils under will be analyzed based on the finite element model. The productions of this study will be capable of predicting the post-construction settlement for those foundations built on peat soil. Consequently effective measures will be suggested based on the results of this study to control and reduce the long-term settlement for the foundations under construction as well as the structures on schedule.