Mechanical and Geophysical Characterization of Damage in Anisotropic Rock

在岩石中，施加应力的变化通常会导致在完整材料中产生新裂纹、从预先存在的裂缝中产生新裂纹或沿预先存在的不连续面沿着而引起的损坏。 最终，预先存在的和/或新产生的裂缝的合并可能导致岩体的破坏。 深地下科学与工程实验室（DUSEL）需要挖掘非常深的大型地下洞穴进行拟议的物理实验。 这种挖掘构成了一个重大的工程挑战，因为前所未有的高应力和大尺寸的洞穴组合。 洞穴将在耶茨地层中挖掘，由于岩石性质的各向异性，这将带来更多的问题。研究的目标是确定：各向异性岩石的断裂机制;剪切裂缝对裂缝聚结的影响;以及使用主动地球物理监测形成之前和期间裂缝的几何和力学特性。 研究结果将为各向异性岩石中的开放和闭合（摩擦）裂缝提供关键的理解，并将支持DUSEL的实验设计，以现场测试这些理论。 该研究是多方面的，包括微观和中尺度的实验观测和测量，并辅以实验的数值模拟。 将进行实验室实验与地球物理监测相结合，以识别和分类各向异性脆性岩石中具有多个非持久性开放和闭合不连续性的系统中的聚结机制，并设计用于确定地震波传输随裂纹萌生、滑动和聚结的变化。 用于实验的材料是来自耶茨地层的岩石，即DUSEL大型洞穴将被挖掘的主岩。 除了DUSEL的好处，这代表了急需的研究，将统一什么是已知的各向同性岩石中的开放和封闭的缺陷，在各向异性岩石中的开放裂缝的断裂。 工程师和地球物理学家的互动是非常可取的，最终必须导致工程技术的应用，地球物理方法和地球物理测量的理论和方法的验证。 这项工作是特别重要的岩石力学领域，没有直接进入岩石受到损害。从研究到学术界和实践的知识转移被整合到一系列模块中，包括所有利益相关者，从K-12到本科生和研究生以及岩石力学专业人员。 该项目的教育推广部分包括对南达科他州铅市的DUSEL进行实地访问。一个由本科生、研究生、当地学校的科学教师和两个PI组成的多元化团体将参加。

In rock, changes in applied stress often result in damage caused by the creation of new cracks in the intact material, initiation of new cracks from pre-existing fractures, or slip along pre-existing discontinuities. Ultimately coalescence of pre-existing and/or newly created cracks can induce failure in the rock mass. The Deep Underground Science and Engineering Laboratory (DUSEL) requires the excavation of very deep large underground cavities for the proposed physics experiments. Such excavation poses a significant engineering challenge because of the unprecedented combination of high stress and the large size of the caverns. The caverns will be excavated in the Yates formation, which opens additional questions because of the anisotropy in rock properties. The objectives of the research are to determine: fracturing mechanisms in anisotropic rock; the effect of shear cracks on fracture coalescence; and the geometrical and mechanical properties of fractures prior to and during formation using active geophysical monitoring. The results of the research will provide key understanding of fracturing for open and closed (frictional) fractures in anisotropic rock, and will support the design of experiments for DUSEL to field-test these theories. The research is multi-faceted, consisting of experimental observations and measurements at the micro- and meso-scales, and complemented with numerical simulations of the experiments. Laboratory experiments coupled with geophysical monitoring will be conducted to identify and classify the coalescence mechanisms in systems with multiple non-persistent open and closed discontinuities in anisotropic brittle rock, and are designed to determine the changes in seismic wave transmission with crack initiation, slip and coalescence. The material used for the experiments is rock from the Yates formation, i.e. the host rock where the large caverns at DUSEL will be excavated. In addition to the benefits for DUSEL, this represents much-needed research that will unify what is known of fracturing of open flaws in isotropic rocks with open and closed flaws in anisotropic rocks. Interaction of engineers and geophysicists is highly desirable and eventually must lead to the application of engineering techniques to geophysical methods and geophysical measurements to the validation of theories and methodologies. The work is particularly important for the field of rock mechanics where there is no direct access to the rock undergoing damage. Knowledge transfer from research to academia and practice is integrated into a series of modules that include all stakeholders, from K-12 to undergraduate and graduate students and to rock mechanics professionals. The educational outreach component of the project includes a site visit to DUSEL in Lead, SD. A diverse group of undergraduate students, graduate students, science teachers in local schools and the two PIs will participate.