Laboratory Controlled Experiments of Rock Fracture and Induced Seismicity

裂缝在自然界的各个尺度上都很重要，从矿物颗粒微裂缝到构造板块边界。它们产生地震，控制流体流动，在工程规模上降低地下结构周围岩石的完整性。地球上的传感器记录下的地震使地震学家能够绘制出地球内部结构的详细图像。同样，在实验室可控条件下收听小尺度的诱导压裂，并使用相同的地震学技术与高频传感器来成像裂缝的生长，并监测它们对岩石变形和流体流动的影响。***本研究将利用一种新的岩石变形装置，该装置可以模拟存在于地球中的三种独立应力，并在高温和流体压力下变形岩石样品。这些样本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。压力容器也便于重复超声成像，因为样品变形到失效。通过变形试验可以控制注入流体的速率和粘度，并且可以测量渗透率。在测试前后，x射线CT扫描和岩石组构分析与超声波成像一起用于解释和验证地震和变形结果。与此同时，适用于岩石压裂的数值模型用于模拟相同的试验，并提供了一种将解释扩展到新场景的方法。******研究将集中在两个环境问题领域，其中受控实验室实验可以增强我们对过程及其控制因素的理解。第一种是水力压裂废水的流体注入，这可能引发有震感的地震，或者提前发生自然过程可能发生的事情。在实验室中进行的流体注入控制实验，将用于研究微裂缝和较大裂缝的相互作用，这些裂缝是由流体和变形过程引发的。第二个领域是三维加载和卸载历史（由开挖引起）对裂隙岩石强度和行为的影响。在这里，来自地下研究实验室的地应力、变形和地震数据将被用于设计压力容器中的三维加载路径，以模拟地下洞口周围开挖损伤区岩石的变形历史。地下研究实验室是为研究放射性废物的深层地质处置而建立的（加拿大、瑞典和芬兰）。这两种尺度的结果将用于验证压裂和流体流动过程的数值模型，并有助于了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.**