中高应变率荷载与高温耦合作用下岩石的动力学特性及能量机制研究

Rock is strain rate material, and underground engineering rocks have to face various kinds of dynamic disturbance along with complicated and changeable temperature environment. The effects of temperature on dynamic mechanical characteristics and energy mechanism of rock have already become a key problem required to settle out in the rock mechanic and rock engineering fields. Therefore, in this project, the research on the dynamic mechanical characteristics and energy mechanism of underground engineering rocks under coupling effects of middle-high strain rate loading and high temperature is carried out, taking experiments as main study means, theories research and numerical analysis as supplementary methods. (1) The experimental technique on high temperature split Hopkinson pressure bar(SHPB) apparatus of 100 mm in diameter is introduced.The dynamic compressive tests and dynamic spilt tests under different temperature conditions are carried out by using of the high temperature SHPB. Then the stress-strain curves are analyzed, and effects of strain rate and high temperature on the laws of the wavy curves, dynamic compressive strength, dynamic spilt tensile strength, and fracture modes are studied. (2)The ultrasonic characteristics of rock under high temperature conditions are investigated. Then the relationships between mechanic parameters, temperature and damage are established. (3) Energy mechanism of rock in the process of deformation and failure under coupling effects of middle-high strain rate loading and high temperature is researched. The laws of accumulation, dissipation, release and transfer of energy are explored to provide a reference for the analysis of the present propagation laws of shock wave and the dynamic failure mechanism in the rock. The fragmentation-energy formula is set up through fragmentation and energy analysis of rock in the process of deformation and failure under coupling effects of middle-high strain rate loading and high temperature. The energy dissipation factor of rock cracking is calculated and the relationship between rock fracture energy and temperature is studied. (4) Based on minimum energy principle of rock, the dynamic failure criterion is established. Then a new damage constitutive model of rock taking the effects of strain rate and temperature into account is established. The results not only impel the development of many subjects such as water conservancy and hydropower engineering, mining engineering, structural engineering, and tunneling engineering but also have very important military significance to the construction and defense of underground defensive engineering, as well as provide a scientific basis for developing and utilizing underground space effectively and rationally. In summary, the project has good social benefit and application prospect.

岩石是应变率材料，地下工程岩石不仅要面对各种动力扰动，而且往往处于复杂的温度环境中。温度对岩石动力学特性及变形破坏的能量机制的影响已成为岩石力学与工程界亟需解决的科学问题。为此，本项目以地下工程岩石为研究对象，以试验为主要研究手段，以理论研究和数值分析为辅助方法，针对岩石在中高应变率荷载与高温耦合作用下的动力学特性和变形破坏的能量机制展开研究：首先，采用高温分离式霍普金森压杆(SHPB)冲击加载实验技术，实现岩石在多种应变率、温度条件耦合作用下的冲击试验，研究高温岩石的静、动态力学性能；其次，研究高温环境下岩石的超声特性和损伤力学特性；再次，研究岩石在中高应变率荷载与高温耦合作用下变形破坏的能量机制和破碎块度的分形特征；最后，基于最小能量原理建立岩石动力破坏准则，构建计及温度和应变率效应的岩石动态损伤本构关系。本项目的研究可为地下岩石工程设计、施工及安全运行提供科学依据。

本项目以地下防护工程常见的三种典型岩石（大理岩、砂岩、花岗岩）为研究对象，基于自行研制的岩石高温冲击加载试验系统，以试验研究、理论研究和数值分析为主要研究手段，结合X射线衍射（XRD）以及扫描电子显微镜（SEM）分析技术，针对岩石在高温与冲击荷载耦合作用下的动力特性和变形破坏的能量机制展开研究，包括：（1）研究了高温处理后岩石的静态物理力学特征随温度的变化规律，分析了岩石声学特征的温度效应，建立了高温后岩石力学性能与声学性能之间的关系，探索了高温与荷载耦合作用下岩石的损伤演化过程；（2）研制了Φ100mm高温分离式霍普金森压杆（SHPB）装置，建立了一套试样独立加温、高温补偿、同步组装等试验操作规程，并进行了实时高温下与高温加热处理冷却后两种不同温度加载路径下岩石的冲击力学试验研究，重点分析了温度和应变率对岩石的动态压缩、劈裂拉伸力学响应以及破坏形态等的影响；（3）运用分形理论对岩石破碎块度的分形特征进行研究，给出了破碎块度分维值与能量吸收的关系式，并分析了岩石的破碎分形维数、破碎块度、能量吸收三者之间的内在联系,研究了岩石动态破碎过程中的能量演化机制；（4）从矿物成分和断口形貌特征的角度入手，运用XRD技术分析了高温加热处理后岩石的组分特征随温度的变化趋势，运用SEM手段分析了高温岩石冲击破坏断口的微观结构特征的变化规律；（5）在常温损伤演化方程的基础之上引入温度影响因素，推导了岩石的高温损伤演化方程，采用组合建模的方法，以损伤力学为基础，将损伤体引入到粘弹性本构模型中，构建了高温下岩石的动态损伤本构模型，并基于试验数据验证了该模型的合理性；（6）针对高温与冲击荷载耦合作用下岩石的冲击压缩、劈裂拉伸力学试验展开有限元数值模拟研究，采用ANSYS/LS-DYNA有限元分析软件再现了冲击应力波在压杆以及试样中的传播过程，进一步探讨了岩石的高温冲击力学行为以及宏观破坏形态的变化规律。