CAREER: Theoretical and Experimental Analysis of Fluid Injection into Granular Media-Failure and Flow Patterns

该学院早期职业发展（Career）项目的研究目标是开发一个综合的理论和实验项目，以表征流体注入致密颗粒介质的过程。这将有助于更好地理解注入流体不仅渗透并置换颗粒介质时的基本破坏机制和流动模式。对这种注入过程的基本理解对于许多民用、环境和石油应用至关重要，例如，用于地基改善的灌浆，用于碳氢化合物回收的水力压裂，用于固体废物处理的钻屑回注，用于环境修复的渗透性反应屏障的建设，以及用于减少温室气体的CO2封存。虽然有大量文献报道了颗粒介质表现为刚性多孔介质或分散在流体中表现为稀悬浮液的两种极限情况，但在密集堆积的颗粒介质中，由于流体流动而发生颗粒位移的注射过程尚未得到很好的理解。该研究是跨学科的，需要来自地质力学、岩土工程、流体力学和软物质物理学等领域的知识。通过实验和理论研究相结合的方法，探索颗粒介质从固体到流体的转变过程。需要解决的基本科学问题包括：(a)建立控制失效/流动状态转变的条件，(b)描述失效/流动几何形状和内部流体压力的演变特征，以及(c)发展标度定律，将结果推广到实际相关条件。实验工作将首先使用新的成像和传感技术来提取颗粒的运动学和流体压力分布。然后将使用离散元法结合流体流动方案对注射过程进行分析。该研究将直接应用于几个重要的工程问题，如地质地层储存能力的确定，以及钻屑安全处置到地下地层的限制。研究结果将发表在学术期刊上，通过与业界合作传播，并纳入本科和研究生课程。鼓励女性学习工程学将是本科教育和拓展活动的主要重点。PI将积极招收女本科生，以获得研究经验。佐治亚理工学院的女性工程项目将为中学女生组织的夏令营开发动手实验。此外，PI将通过佐治亚理工学院综合科学、数学和技术教育中心，邀请一名当地高中教师进行夏季研究，并开发一个基于地质力学/岩土工程的软件模块，用于新的环境科学和地球系统课程，以提高格鲁吉亚K-12教育的表现标准。该软件将通过乔治亚州科学教师协会会议进行传播。如上所述，流体注入颗粒介质的过程与许多工程应用有关。然而，人们对注入流体的流动模式和最终命运知之甚少，这在许多情况下导致了重大的安全问题。这项研究将导致对这些问题的更清晰的理解，以及不再主要基于经验数据的更安全的工程实践。来自斯伦贝谢和Algenol生物燃料公司的工业合作者将帮助将研究成果转化为工程实践。

The research objective of this Faculty Early Career Development (CAREER) Program award is to develop an integrated theoretical and experimental program to characterize the process of fluid injection into dense granular media. This will lead to a better understanding of the fundamental failure mechanisms and flow patterns in the regimes when the injected fluid not only permeates through, but also displaces, the granular media. Fundamental understanding of such an injection process is crucial to many civil, environmental, and petroleum applications, e.g., grouting for ground improvement, hydraulic fracturing for hydrocarbon recovery, drill cuttings reinjection for solid waste disposal, construction of permeable reactive barriers for environmental remediation, and CO2 sequestration for greenhouse gases reduction. While extensive literature exists for the two limiting cases when granular media either behave as rigid porous media or are dispersed in a fluid to behave as a dilute suspension, the injection process in densely packed granular media, where grain displacements occur due to fluid flow, is not yet well understood. The research is interdisciplinary, requiring knowledge from the fields of geomechanics, geotechnical engineering, fluid mechanics, and soft matter physics. The transition in granular media behavior from solid-like to fluid-like will be explored through an integrated experimental and theoretical research approach. Basic scientific issues to be addressed include: (a) establishing conditions that govern the transition of failure/flow regimes, (b) characterizing the failure/flow geometry and the evolution of internal fluid pressure, and (c) developing scaling laws to generalize the results for conditions of practical relevance. Experimental work will first be conducted with novel imaging and sensing techniques to extract grain kinematics and fluid pressure distribution. The injection process will then be analyzed using the Discrete Element Method coupled with fluid flow schemes. The research will have direct application to several significant engineering problems, such as the determination of geological formation storage capacity, and the limits to the safe disposal of drill cuttings into subsurface formations. Results from the research will be published in scholarly journals, disseminated through collaboration with industry, and integrated into undergraduate and graduate courses. Encouraging women to pursue engineering will be the main focus of undergraduate education and outreach activities. The PI will actively recruit women undergraduate students to gain research experiences. Hands-on experiments will be developed for summer camps organized for middle school girls by Georgia Tech's Women in Engineering Program. In addition, the PI will host a local high school teacher, through the Georgia Tech Center for Education Integrating Science, Mathematics, and Technology, to conduct summer research and to develop a geomechanics/geotechnical engineering based software module to be used in the new Environmental Science and Earth Systems courses, to improve the performance standards in K-12 education in Georgia. The software will be disseminated through the Georgia Science Teachers Association conference. The process of fluid injection into granular media is relevant to many engineering applications, as cited above. However, the pattern of flow and eventual fate of the injected fluids is poorly understood, leading to significant safety concerns in many situations. This research will lead to a clearer understanding of these issues, as well as safer engineering practices that are no longer based primarily on empirical data. Industrial collaborators from Schlumberger and Algenol Biofuels will help translate the research findings into engineering practice.