EAGER: Exploratory Research on Rock Damage from Geologic and Induced Thermal Loading

在岩石科学和工程学科中，岩石在短期和长期热漂移下的行为是一个关键的知识缺口。这种先进的认识在许多应用中将是重要的，包括采矿和民用挖掘、就地资源开采或地热开发，为此将在高温下将挖掘延伸到岩石中。大多数分析都集中在构造和深度造成的岩石应力上。随着对热变化如何影响岩石结构和结构的深入了解，新的挖掘方法和技术可能会被开发出来，从而导致真正的热诱导岩石破碎的工程化设计。要研究的最相关的问题是：完整岩石(和岩体)的压力-热(PT)历史如何导致破坏和影响行为？哪些机制是影响受热岩石力学结构变化的最重要因素？这些机制如何影响可开挖性、稳定性和强度？这个初步构想的探索性研究奖助金项目涉及地质学、土木工程和采矿工程，以及提炼冶金和矿物加工。这种多学科的方法将有助于扩大未被充分代表的群体在研究中的参与，并对工程教育产生积极影响。诱发损害的评估将包括具有明确的热和应力历史和成分的岩石。岩石样品将在干燥和饱和状态下接受额外的选择性热处理(例如微波)，并将使用薄片岩石学、光学阴极发光、扫描电子显微镜和自动矿物学来评估由此造成的损害和性能变化。对热历史和应力历史造成的地质损害的调查(例如，局部变质作用接触带中的矽卡岩、伟晶侵入体)将研究岩心和采矿暴露的样品。温度和压力历史将使用矿物对的地热压力法进行评估，并根据现有的热年代学研究(例如磷灰石和锆石的U-Pb/He热年代学)放在区域范围内。这些结果将与实验1的结果进行比较，以确定加热引起的晶界开裂行为和应力和损伤的产生。最后，对热载荷的数值模拟进行了数值分析，并将结果与实验观测结果进行了比较。

The behavior of rock under short- and long-term thermal excursions is a critical knowledge gap in rock science and engineering disciplines. Such advanced understanding will be important in many applications, including mined and civil excavations, in situ resource extraction or geothermal development for which excavations will be extended into rock masses at elevated temperatures. Most analyses have focused on rock stress as result of tectonics and depth. With insight into how thermal changes influence the fabric and structure of the rock, new excavation methods and technologies may be developed that lead to a truly engineered design of thermally-induced rock breakage. The most relevant questions to be investigated are: How does the PT (Pressure-Thermal) history of intact rock (and a rock mass) induce damage and influence behavior? Which mechanisms are most important in influencing the changes in mechanical structure of heated rock? How do these mechanisms influence excavatability, stability and strength? This EArly-concept Grant for Exploratory Research (EAGER) project involves geology, civil and mining engineering, and extractive metallurgy and mineral processing. This multi-disciplinary approach will help broaden participation of underrepresented groups in research and positively impact engineering education.The assessment of induced damage will involve rocks with well-defined thermal and stress history and composition. Rock samples will be subjected to additional selective heat-treatment (e.g., microwaves) in dry and saturated states, and the resulting damage and changes in properties will be evaluated using thin section petrography, optical cathodoluminescence, scanning electron microscopy and automated mineralogy. Investigations of geologic damage caused by thermal and stress history (e.g., skarns in the contact zone of local metamorphism, pegmatitic intrusions) will study samples from core and mined exposures. The temperature and pressure history will be evaluated using geothermobarometry of mineral pairs and placed in regional context based on existing thermochronology studies (e.g. U-Pb/He thermochronology of apatite and zircon). These results will be compared with those from experiment 1) to identify cracking behavior and generation of stresses and damage at grain boundaries as result of heating. Finally, numerical simulation of thermal loading of will be analyzed numerically and the results will be compared to the experimental observations.