岩土材料热软化与热硬化力学特性的统一本构模型研究

The influence of temperature change on the strength and deformation of geomaterials, which controls the safety of the geotechnical engineering relating to temperature effect, is growing increasingly attention in the engineering field. The mechanical behavior of geomaterials suffered from high temperature can not only show thermal-softening behavior (The higher the temperature is, the weaker the strength is), but also thermal-hardening behavior (The higher the temperature is, the stronger the strength is). Unfortunately, there is not still a constitutive model to describe this phenomenon. In this study, a systematic laboratory soil tests are firstly carried out to investigate the thermal properties of geomaterials and reveal the mechanism of thermal-softening and thermal-hardening behavior due to temperature change. Based on the test results, a simple and unified thermo-elastoplastic model, which can describe the thermal-softening and thermal-hardening behavior of geomaterials, is proposed by casting into the factor of the thermal-softening and thermal-hardening behavior and modifying the evolutional rule of state variables. This basic research will deepen the cognition of unified thermo-mechanical behavior of geomaterials, and provide the theoretical basis and technical support to the engineering problem relating to thermal effect. Therefore, this project has important scientific value and wide engineering application.

高温引起岩土材料的力学特性变化直接影响着涉及温度效应的岩土及地下工程的安全性问题，日渐受到工程界的重视。高温对岩土材料的作用，既有表现为热软化（温度升高，材料强度减弱）行为，也有表现为热硬化（温度升高，材料强度增强）行为，但至今仍未有一个可以统一描述这一现象的热弹塑性本构模型。针对这一现状，本项目首先通过进行系统的岩土材料高温土工试验，分析和总结出温度变化对岩土材料力学特性的影响规律，揭示导致发生热软化与热硬化现象的关键原因，并将其进行定量化描述；然后在试验数据的基础上，通过增加温度引起岩土材料产生热软化与热硬化的变化规律及修正相关状态变量发展式，对既有热弹塑性本构模型进行修正，从而建立一个简洁且可统一描述岩土材料热软化与热硬化力学特性的弹塑性本构模型。该项研究工作将深化认识岩土材料热力耦合共性问题，为解决一些相关领域的工程问题提供理论基础和技术支撑，具有重要的科学价值和广阔的应用前景。

温度变化对岩土材料的强度和变形特性直接影响着涉及温度效应的岩土及地下工程的安全性问题，已日渐受到工程界的重视。在高温作用下，岩土材料的强度特性既可以表现为热软化（温度升高，材料强度减弱）行为也可以表现为热硬化（温度升高，材料强度增强）行为，但至今仍未有一个可以统一描述这一现象的热弹塑性本构模型。针对这一现状，本项目首先通过进行了系统的岩土材料高温土工试验，分析和总结了温度变化对岩土材料力学特性的影响规律，揭示了产生热软化与热硬化现象的物理力学机理；然后在试验数据的基础上，通过嵌入温度引起岩土材料产生热软化与热硬化因素及修正相关状态变量发展式，对既有热弹塑性本构模型进行修正，从而建立了一个简洁且可统一描述岩土材料热软化与热硬化力学特性的弹塑性本构模型。开发了热水力三相有限元耦合程序，并将新建的本构模型导入了有限元程序中。通过有公开发表的涉热岩土工程的数值模型，验证了所提出模型的有效性。该项研究工作深化认识了岩土材料热力耦合共性问题，为解决一些相关领域的工程问题提供理论基础和技术支撑，具有重要的科学价值和广阔的应用前景。