Damage of Underground Rocks Due to Engineering Activities

加拿大经济严重依赖自然资源，其直接和间接贡献了名义GDP的20%和180万个工作岗位(加拿大统计局，2014)。这些工作和活动大多与地下岩石的挖掘有关。在世界范围内，岩石工程项目的深度增加是一个趋势。例如，世界上十个最深的矿井中有两个(Kidd Creek和Creighton)都位于加拿大安大略省。这些地雷的深度超过2公里。 世界范围内岩石工程项目日益深入的趋势导致了严重的安全问题，从而对加拿大经济造成了不利影响。增深对工程结构安全的影响有两个方面：一是开挖过程扰动了岩体的应力状态，破坏了地下洞室周围的岩石材料；二是受损的岩石材料受到高地应力和附近工程活动扰动的共同作用，容易发生灾难性破坏。 申请人研究计划的长期目标是，主要采用实验方法，全面了解地下岩石在热、水文和机械载荷共同作用下的损伤及其对地下岩石工程结构安全的影响。在前人研究的基础上，该项目的短期目标是(1)揭示应力损伤的一般机制，(2)了解应力损伤岩石的力学响应。将建立描述岩石损伤为应力历史或应力路径的函数的定量定律。此外，还将研究应力损伤岩石材料的响应。 为了实现研究目标，确定了三个研究课题：任务1.利用岩体模拟材料制成的板模拟地下开挖；任务2.开挖引起的岩板中的损伤分布和量化；任务3.模拟地下条件下应力损伤岩石材料的静态和动态试验。当前方案的创新之处包括首次设计了高速、非接触测量的实验室开挖试验，并使用了一种岩石模拟材料作为物理模型。 深部高地应力条件下，需要进行详细有效的力学分析。人们通常求助于数值模拟，在岩石力学中出现了数值模拟研究的热潮。然而，开发的数值代码需要针对高度受控和充分配备仪器的实验室实验，对其假设、算法和材料模型进行有力的验证。因此，这项建议计划在实验上模拟地下开挖过程，并为数值研究提供基准，这对岩石力学和岩石工程至关重要。

The Canadian economy heavily depends on natural resources, which directly and indirectly accounted for 20% of nominal GDP and 1.8 million jobs (Statistics Canada 2014). Most of these jobs and activities are associated with the excavation of underground rocks. There is a worldwide trend for depth increasing in rock engineering projects. For example, two of the ten deepest mines in the world ( Kidd Creek and Creighton) are both located in Ontario, Canada. These mines are over 2 km deep. The worldwide trend of increasing depth in rock engineering projects leads to grand safety concerns, and therefore adverse implications to Canadian economy. The effects of increasing depth to the safety of engineering structures are two folds: first, the excavation process disturbs the stress state of the rock masses and thus damage the rock materials around the underground openings; second, the damaged rock material is under combined action of high in situ stresses and disturbances induced by nearby engineering activities and is thus prone to catastrophic failures. The long-term goal of the applicant's research program is to fully understand the underground rock damage due to coupled thermal, hydrological, and mechanical loads and its consequences on the safety of underground rock engineering structures using mainly experimental methods. Built on previous studies, the short-term objective of this project is (1) to reveal the generic mechanisms of stress-damage and (2) to understand the mechanical response of stress-damaged rocks. Quantitative laws describing the rock damage as a function of the stress history or the stress path will be established. In addition, the response of stress-damaged rock materials will be investigated. To achieve the research objective, three research topics are identified: Task 1. Simulated underground excavation using a plate made of rock mass analogue material; Task 2. Damage distribution and quantification in the rock plate due to excavation; Task 3. Static and dynamic tests of stress-damaged rock materials under simulated underground conditions. The novelties of the current proposal include the first design of the laboratory excavation test with high speed, non-contact measurements, and the usage of a rock mass analogue material for the physical model. Deep underground conditions with high in situ stress require detailed and valid mechanical analysis. People usually resort to numerical simulations and there has been a surge in numerical simulation study in rock mechanics. However, the numerically codes developed need vigorous validations of their assumptions, algorithms, and material models against highly controlled and adequately instrumented laboratory experiments. This proposal thus plans to experimentally mimic the underground excavation process and provide benchmarks for numerical studies, which is essential for the rock mechanics and rock engineering.