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.
