冻土力学行为的能量表征方法与本构模拟研究

To reveal the energy characteristics of mechanical behavior of frozen soil, directly determine its thermodynamic functions based on objective laws of permafrost energy with the thermodynamic constraints, and improve the application of thermodynamic methods on constitutive modeling for frozen soil, this project is intended to develop an experimental method and thermodynamic theory on the basis of the current frozen soil mechanical experimental methods and elasto-plastic constitutive theory. Our experimental and theoretical study can reveal the energy characteristics of mechanical behavior of frozen soils, and investigate the energy evolution laws and its influencing factors of mechanical behavior of frozen soil. Additionally, we can propose characterizing method for mechanical behavior of frozen soil, and study the theory and analysis method capable to determine thermodynamic function of frozen soil. Lastly, we will establish coupling thermodynamic constitutive model for frozen soil in rigorous form. The achievements from this research will play an important role in deeply understanding of the complex thermodynamic and thermo-mechanical behavior of frozen soils, precisely simulating its behaviors by the proposed constitutive model, and applying thermodynamic theory to constitutive model for frozen soils. The practical application of this study has an important scientific significance on the structure calculation and design in frozen soil regions.

为揭示冻土力学行为的能量特征,在热力学约束下根据冻土能量客观规律直接确定冻土热力学函数,完善热力学方法在冻土本构模拟中的应用，本项目拟在现有冻土力学试验方法和弹塑性本构理论的基础上，开发与热力学理论相适应且可揭示冻土力学过程中能量特征的试验方法，探明冻土力学行为的能量演化规律及影响因素，提出冻土力学行为的能量表征方法，在热力学体系下研究直接确定冻土热力学函数具体形式的理论和分析方法，建立真正意义上的冻土热力学本构模型。本项目的研究成果将对深入认识冻土复杂热力行为并对其进行准确的本构模拟、热力学理论在材料本构模拟中的实际应用两方面均具有重要科学意义，也对冻土工程结构计算与设计具有实际的应用价值。

为在不可逆热力学体系下考察冻土热力行为并建立其本构模型，本项目以冻结根河粉质黏土为研究对象，研究了确定冻土在受荷变形过程中热耗散能、弹性应变能、塑性应变能的试验方法及相应的能量特征分析方法，应用所提出的试验方法对冻结根河粉质黏土开展了不同应力路径下的三轴试验，结合热力学理论与试验结果研究了冻结根河粉质黏土的力学行为与能量特征及其二者的关系，研究了冻结粉质黏土四种硬化参量等值线形态及其对相关联流动准则的适用性。主要研究结果包括提出了冻土受荷变形中的热耗散测试方法，基于常围压三轴压缩试验的两种控制模式，对只能采取应力控制模式的应力路径试验提出了确定其加载速率的方法，提出了不影响冻土力学性质的应力路径循环加卸载试验方法，提出了基于常规三轴压缩试验数据确定冻土中冰胶结力的方法；揭示了冻结根河粉质粘土不同应力路径下弹性应变能和塑性应变能随应变的演化规律，结合热力学方法与弹塑性理论提出了确定热力学函数具体形式的方法；对比冻结粉质黏土的塑性剪应变、塑性体变、塑性总应变、塑性功四种硬化参量等值线与塑性势的关系揭示了不同硬化参量是否符合关联流动法则的原因。本项目的研究成果对促进更加普适的热力学理论在冻土中的应用提供了试验技术、分析方法。