岩石损伤演化过程中的动态热传导机理研究

The dynamic evolution of heat conduction with rock damage evolution process is an important scientific issue involved in rock mass engineering considering heat transfer process, such as geological disposal of nuclear waste, et al. At present, the evolution characteristics and mechanism of rock damage evolution on heat conduction is still unclear. The proposed project focuses on Beishan granite in Gansu province, which is the most important candidate site of radioactive waste disposal repository in China. Uniaxial loading and heat conduction parameters measurement will be conducted to study the dynamic influence characteristics of rock damage on heat conduction using acoustic emission techniques. Multiaxial loading test and heat conduction parameters measurement will be conducted to study the influence mechanism of mesoscopic damage characteristics on rock heat conduction. A dynamic heat transfer model for damaged rock mass will be proposed based on the evolution equations of heat conduction parameters. The model will be calibrated by laboratory test data and realized numerically. The model will be preliminarily applied to the prediction of long term stability analysis of Beishan radioactive waste disposal repository. Research achievement of the proposed project can provide theoretical support to the understanding of evolution characteristics and mechanism of damaged rock heat conduction, and the precise calculation of multi field coupling process in damaged rock mass.

在核废料处置等涉及热能传输的岩体工程实践中，开挖扰动等引起的围岩损伤将导致其热传导特性发生动态调整，进而影响温度场的形成与演化过程。目前损伤演化过程对岩石热传导特性影响的动态规律与机理尚不清晰。项目以我国核废料处置库预选场甘肃北山花岗岩为研究对象，开展岩石单轴加载下的全变形过程声发射监测及热传导特性测试试验，揭示岩石损伤演化过程对热传导特性影响的动态规律；开展细观多轴加载下岩石损伤破裂显微观测及热传导特性测试试验，阐明岩石损伤破裂特征对热传导特性影响的细观机理；建立热传导参数随损伤的演化方程，构建损伤岩石动态热传导模型，基于室内试验数据验证模型的准确性，开发耦合程序模块，将模型初步应用于甘肃北山核废料处置库的长期稳定性预测模拟中。项目成果可为阐明损伤岩石热传导特性的演化规律与机理提供理论基础，为损伤岩体多物理场耦合演化的精准计算提供科学依据。

在涉及热能传输的岩体工程实践中，由开挖卸荷扰动等引起的围岩微裂纹萌生、扩展和损伤积累势必导致其热传导特性发生改变，进而影响温度场的形成与演化过程。本项目以核废料地质处置为工程背景，围绕岩石损伤演化过程中的动态热传导机理这一科学问题，综合室内试验、模型建立与数值模拟等手段，开展了岩石损伤过程对其导热特性影响的宏观规律、机理及模型的相关研究，获得了如下主要结果：1）揭示了力学损伤下岩石传热能力的宏观劣化规律，损伤诱导的导热能力各向异性特征，及饱水处理对损伤前后岩石导热能力的差异性影响。2）借助声发射监测手段与高精度光学扫描导热系数测试方法，揭示了岩石损伤破裂对其导热特性空间分布特征的影响机理，明确了导热系数降低区域与声发射事件表征的损伤破裂区域对应关系，及导热非均匀因子随损伤的演化特征。3）建立了损伤岩石热传导参数演化模型，描述了岩石导热系数随损伤参量的演化规律。4）针对中国北山高放核废料处置库，构建了破裂岩体等效导热系数的数值计算方法，并提出了考虑破裂发育程度、破裂面接触热阻与完整岩石导热系数的破裂岩体等效导热系数简明计算模型。本项目的研究成果可为包括核废料地质处置、高地温地下工程与矿山开采、深层地热资源开发在内的岩体工程多场耦合计算分析，提供关键的理论支撑。