城市环境下黏性土的热力学行为及其微观响应机理研究

项目以城市发展产生温度升高引发的热灾害日益凸显为背景，以深化认知城市环境下黏性土的热力学行为及其微观机理为主线，采用“温度影响+宏、中、微观试验→机理分析→指导与应用”的研究思路，研制温控原位孔内剪切设备，开展变化温度场影响的原位力学试验，提出考虑温度效应的原位力学参数确定方法，评价黏性土的持热与导热性能;开展恒温、升温与升、降温循环三种热路径的热固结与动、静三轴试验，研究温度对黏性土变形规律与强度特性的控制影响，提出热硬化或热软化产生的温度条件；明晰温度效应产生的物质基础，提出主控温度效应的热敏组分；借助环境扫描电镜与温控热台，开展温度变化的微观结构动态跟踪测试，分析不同热路径下微观结构的演化规律，寻找到对温度最敏感的微结构参数，建立其与宏、中观力学参数的相关性与敏感性分析，阐明城市环境下黏性土热力学行为的微观响应机理，为科学治理和调控城市热灾害，实现城市的可持续发展提供理论技术支持。

Thermal disasters related to temperature effect have become more and more serious with the speedup of the urbanization process. In this project, based on various macro, meso and micro tests, a thermal-mechanical coupling mechanism would be analyzed, aiming to gain an insight into thermal and mechanical behaviour of clayey soil in urban environment. This study is organized in the following way. Firstly, a new test equipment for borehole shear test was developed by adding temperature control system, in-situ thermal-mechanical tests at different temperatures are conducted for evaluating thermal stability and conductivity of clayey soil, and a method for obtaining in-situ parameters considering temperature effect is also proposed. Afterwards, thermal consolidation and static and dynamic triaxial test are conducted in three temperature path conditions, including constant temperature, rise temperature and up-down temperature cycle. The rule and influence of temperature to deformation and strength characteristics of clayey soil are studied, and the occurred conditions for heat softening or hardening are discussed. The material factors that lead to temperature effect and the temperature-sensitive physical or chemical composition are investigated. Furthermore, real-time tracing tests for microstructure are conducted for studying microstructure evolutionary process, using the environmental scanning electron microscope (ESEM) and temperature control stages. Finally, based on the experimental findings, a temperature-sensitive microstructure parameter is proposed in order to create the relationship between microstructure evolutionary and mechanical behavior, the mechanism for thermo-mechanical behaviour of clayey soil are revealed consequently. The results of this research project are helpful to offer the theoretical and technical support for controlling thermal urban disasters and promote urban sustainable development.