Laboratory Controlled Experiments of Rock Fracture and Induced Seismicity

从矿物颗粒微裂缝到构造板块边界，裂缝在自然界的所有尺度上都是重要的。它们制造地震，控制流体流动，并在工程规模上降低地下结构周围岩石的完整性。通过在地球各地的传感器上记录地震，地震学家可以创建地球内部结构的详细图像。以类似的方式，可以在实验室中在受控条件下收听小规模的诱导压裂，并使用具有高频传感器的相同地震学技术来成像裂缝的生长并监测其对岩石变形和流体流动的影响。*这项研究将利用一种新型的岩石变形装置，该装置可以模拟地球上存在的三种独立的应力，并在高温和流体压力下使岩石样品变形。样品被装在一个压力容器中，该容器使用高频监听设备通过定位实验室地震来监测裂缝的产生。当样品变形到失效时，压力容器还便于重复超声成像。注入流体的速度和粘度是可以控制的，通过变形试验可以测量渗透率。在测试过程中，使用了测试前后的X射线、CT扫描和岩组分析，并结合超声波成像对地震和变形结果进行了解释和验证。同时，适用于岩石破裂的数值模型被用来模拟相同的测试，并提供了一种将解释扩展到新情景的方法。*这项研究将集中在两个环境关注的领域，在这两个领域，受控的实验室实验可以增强我们对过程和什么控制过程的理解。第一种是水力压裂废水的注液，这可能会引发有感地震，或及时将自然过程可能发生的情况提前。在实验室中对产生的裂缝进行注液控制实验，将用于研究微裂缝与较大裂缝的相互作用，当流体和变形过程触发时，这些裂缝会滑动。第二个领域是3D加载和卸载历史，由挖掘的产生，对破裂岩石的强度和行为的影响。在这里，来自地下研究实验室(加拿大、瑞典和芬兰)的地应力、变形和地震数据将被用来设计压力容器中的3D加载路径，以模拟地下洞口周围开挖损伤区中岩石的变形历史。这两个尺度的结果将用于验证压裂和流体流动过程的数值模型，并有助于理解这些过程如何从实验室扩展到现场条件。**

Fractures are important at all scales in nature from mineral grain micro-cracks to tectonic plate boundaries. They create earthquakes, control fluid flow and at the engineering scale reduce the integrity of rock around underground structures. The recording of earthquakes on sensors all around the earth has allowed seismologists to create detailed images of the internal structure of the earth. In a similar way, it is possible to listen to small scale induced fracturing in the laboratory under controlled conditions and use the same seismology techniques with high frequency sensors to image the growth of fractures and monitor their effect on rock deformation and fluid flow. ***This research will utilize a novel rock deformation apparatus that can simulate the three independent stresses that exist in the earth and deform samples of rock at elevated temperatures and fluid pressure. The samples are contained in a pressure vessel that uses high frequency listening devices to monitor the creation of fractures by locating laboratory earthquakes. The pressure vessel also facilitates repeated ultrasonic imaging as the samples are deformed to failure. The rate and viscosity of fluid injection can be controlled, and measurements of permeability are possible through out the deformation tests. Pre and post testing X-ray CT scans and petrofabric analysis are used together with ultrasonic imaging during the tests for the interpretation and validation of the seismic and deformation results. In parallel, numerical models appropriate to fracturing in rock are used to model the same tests and provide a method for extending interpretations to new scenarios.******The research will focus on two areas of environmental concern where controlled laboratory experiments can enhance our understanding of the processes and what controls them. The first is fluid injection of wastewater from hydraulic fracturing which can trigger felt earthquakes or bring forward in time what may have happened by natural processes. Controlled experiments of fluid injection in the laboratory, on created fractures, will be used to study the interaction of microcracking and larger fractures that slip when triggered by fluid and deformation processes. The second area is the effect of 3D loading and unloading history, induced by the creation of excavations, on the strength and behavior of fractured rock. Here, in situ stress, deformation and seismic data from Underground Research Laboratories, built to study deep geological disposal of radioactive waste (Canada, Sweden and Finland), will be used to design the 3D loading path in the pressure vessel to simulate the deformation history of rock in excavation damage zones surrounding underground openings. Results at both scales will be used to validate numerical models of fracturing and fluid flow processes and contribute to understanding how these processes scale from the laboratory to in situ conditions.**