Mechanical and Geophysical Characterization of Damage in Anisotropic Rock

在岩石中，外加应力的变化通常会导致破坏，这是由于在完整的材料中产生新的裂缝，从先前存在的裂缝中引发新的裂缝，或者沿着先前存在的不连续面滑动造成的。归根结底，预先存在的和/或新产生的裂隙的结合会导致岩体的破坏。深部地下科学与工程实验室(DUSEL)要求为拟议的物理实验挖掘非常深的大型地下洞穴。这种开挖带来了巨大的工程挑战，因为前所未有的高应力和巨大的洞穴结合在一起。这些洞穴将在耶茨地层中挖掘，由于岩石性质的各向异性，这带来了更多的问题。这项研究的目的是确定：各向异性岩石中的破裂机制；剪切裂缝对裂缝结合的影响；以及利用主动地球物理监测在形成之前和期间裂缝的几何和力学性质。研究结果将提供对各向异性岩石中开放和闭合(摩擦)裂缝压裂的关键认识，并将支持Dusel现场测试这些理论的实验设计。这项研究是多方面的，包括微观和中观尺度的实验观测和测量，并辅之以实验的数值模拟。结合地球物理监测，将进行实验室实验，以识别和分类各向异性脆性岩石中具有多个非持续开放和闭合不连续结构面的系统中的合并机制，并旨在确定地震波在裂纹萌生、滑动和合并过程中的传播变化。实验使用的材料是来自叶茨组的岩石，也就是将在杜塞尔挖掘大型洞穴的寄主岩石。除了对Dusel的好处外，这是一项亟需的研究，将把各向同性岩石中开放缺陷的破裂与各向异性岩石中开放和封闭的缺陷统一起来。工程师和地球物理学家之间的互动是非常可取的，最终必须导致将工程技术应用于地球物理方法，并将地球物理测量应用于验证理论和方法。这项工作对于岩石力学领域尤其重要，因为在该领域中，无法直接接触到正在遭受破坏的岩石。从研究到学术和实践的知识转移被整合到一系列模块中，其中包括从K-12到本科生和研究生以及岩石力学专业人员的所有利益相关者。该项目的教育宣传部分包括对南达科他州铅的杜塞尔进行实地访问。一群不同的本科生、研究生、当地学校的科学教师和两个PI将参与其中。

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.