温度-应力历程对花岗岩裂隙渗透性影响机理研究

The fractured rock mass is under constantly changing temperature and stress condition in many deep underground engineering such as high-level radioactive waste disposal engineering. Thus the rock mass will undergo complicated loading-unloading condition, which brings great challenge in studying the evolution of hydraulic conductivity of rock mass and its influence on underground engineering. In this context, many flow tests under various temperature and stress conditions will be firstly carried out, and the numerical and theoretical studies will be conducted to reveal the influence of temperature, the history of temperature and stress on the hydraulic conductivity of Beishan granite fractures. Then, the meso-contact mechanical model will be built according to statistical parameters of fracture surface geometry. Based on the elastoplastic damage mechanics, and taking the influence of temperature, the history of temperature and stress into account, the deformation and hydraulic conductivity model of rock fracture will be proposed to describe the influence of loading history. At last, the proposed deformation and hydraulic conductivity model of rock fracture will be verified and embedded into a numerical software. And the influence of the changing temperature and stress environment on the long-term safety will be evaluated for the high-level waste geological repository. The achievements are expected to provide theoretical and technical support for the evaluation of the long-term safety and production efficiency of related deep underground engineering.

在高放废物处置等深部地下工程中，工程引起岩体所处的温度环境反复变化，导致应力环境同步改变，使裂隙岩体经历复杂的温度-应力加卸载过程，为准确认识裂隙岩体渗透性演化规律及其对工程的影响带来挑战。针对这一科学问题，本项目拟以甘肃北山花岗岩裂隙试样为研究对象，开展多种温度条件下加卸载渗流试验，结合数值模拟和理论分析，揭示温度-应力历程对花岗岩裂隙渗透性的影响规律和内在机理；进而，根据裂隙面形貌统计参数建立细观接触模型，基于弹塑性力学和损伤力学，融合温度、温度历史和应力历史的影响，建立可表征裂隙温度-应力历程影响的变形渗流模型；最后，验证提出的模型并编译嵌入数值计算软件，分析温度-应力演化对高放废物处置等深部地下工程长期安全性的影响。研究成果可为相关深部地下工程安全性和生产效率评价提供理论和技术支撑。

针对高放废物地质处置等深度地下工程中，工程引起岩体温度和应力反复变化条件下岩体裂隙变形和渗透性演化规律及内在机制的关键科学问题，以北山花岗岩为研究对象，主要开展了中等温度条件下力学行为、升降温过程矿物颗粒尺度温度-变形-热破裂过程、中等温度条件下热愈合效应研究、升降温过程花岗岩渗流特性以及变温-变应力路径北山花岗岩裂隙渗流试验及理论研究。主要取得以下成果：（1）发现北山花岗岩在高放废物处置温度范围内出现“热愈合”效应，表现为强度强化、渗透性降低和孔隙闭合，有利于高放废物处置库长期稳定和密闭；（2）基于应变记忆效应，通过DRA方法及核磁共振揭示力损伤花岗岩“热愈合”效应内在机理，中等温度条件下矿物颗粒非均匀变形使力损伤花岗岩细观结构调整，降低孔隙率，增大矿物颗粒接触面，形成“围压效应”，使花岗岩强度强化-渗透性弱化；（3）搭建了温度-微变形-热破裂监测系统，从矿物尺度分析了升降温全过程不同矿物颗粒的温度场、变形和热破裂过程，结合离散元数值模拟，认识了升降温过程花岗岩矿物尺度温度-变形-热破裂过程及内在力学机理；（4）联合研制了“微机控制岩石节理高温剪切渗流耦合试验系统”，并采用该装置开展了变温-变应力路径下北山花岗岩裂隙渗流试验，认识了花岗岩裂隙在高放废物地质处置温度范围渗流特性响应规律，结合结构面演化特征分析了其内在机制，并建立了考虑温度和应力裂隙渗流模型；（5）采用COMSOL、FLAC3D和PFC等数值模拟软件研究并验证了相关模型，并对高放废物地质处置典型型式的物理场演化进行了模拟。本项目取得的认识可对高放废物地质处置长期安全性评价提供支撑。.依托本项目共发表论文8篇，其中SCI期刊论文4篇，中文核心论文4篇，申请国家发明专利2项，培养已毕业研究生3名，在读研究生3名。完成了结题报告。