June 26, 2011
June 26, 2011
June 29, 2011
22.1717.1 - 22.1717.12
X-Ray Computed Tomography: A New Pedagogical Tool for Studying Micro and Macro Geomaterial PropertiesAbstract:The mechanical behavior of granular soils is highly dependent on the particle microstructure.The microstructure is commonly referred to as the soil fabric, which includes the shape,distribution, and arrangement of particles and void space. Because of the inherent difficulties inmeasuring soil properties on a microscale, geotechnical engineers use macro properties toestimate, or predict, the response of soil when subjected to changes in the state of stress. Thesemacro properties (void ratio, porosity, density, uniformity, etc.) are used to represent gross oraverage measures of the soil microstructure in terms of engineering behavior; i.e., strength,compressibility, and permeability.Civil engineering students learn about basic geomaterial properties in the introductorygeotechnical engineering or soil mechanics course, which is typically taken during the junioryear of the Bachelor of Science degree program. Introductory soils courses most often includelaboratory sessions in which students conduct simple destructive tests such as sieve analyses,Atterberg limits, and compaction tests. Unfortunately, there is no standardized or readilyimplementable test for evaluating the engineering influence and significance of soil fabric andmicro properties. Textbooks and instructors emphasize the importance of soil texture, void ratio,porosity, and phase relationships; however, students often struggle with the physical meaningand significance of these fundamentally important parameters.This paper presents a novel approach for implementing x-ray computed tomography (x-ray CT)in introductory soil mechanics courses. Systematic methods are described for using non-destructive x-ray CT in introductory soils courses to quantify microscale measurements of localvoid ratio distribution, gradation, pore size distribution, and relative density of scanned digitalimages. Primary benefits of this approach include: 1) Students visually perceive and quantify relationships between particulates and voids. 2) Students attain a better understanding of the mechanical properties of soils through laboratory experiments that include both simple destructive empirical tests and nondestructive techniques using advanced technologies that are destined to become prevalent during their careers. 3) Students are excited about learning a relatively advanced technology that is readily adaptable to a wide range of cross-disciplinary applications.It has been the primary author’s experience that engaging geo-students in the use of x-ray CTtechnology helps alleviate a common issue in the geotechnical discipline; which is, somestudents lose interest early in the semester because of the simple, low-tech (crude), testing that istypically conducted during the first few weeks in introductory soils courses. The high-techflavor of x-ray CT can be attractive to these students. An additional attribute of this approach isthat the procedures described herein can be implemented at a relatively minimal cost using opendomain software and raw digital images available from databases. Consequently, theseexperiments can be implemented by engineering departments regardless of their accessibility toan x-ray CT scanner.
Mokwa, R. L., & Morris, Z. L., & Lutey, W. A. (2011, June), X-Ray Computed Tomography: A New Pedagogical Tool for Studying Micro and Macro Geomaterial Properties Paper presented at 2011 ASEE Annual Conference & Exposition, Vancouver, BC. https://peer.asee.org/18395
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