Weathering of Igneous, Metamorphic, and Sedimentary Rocks in a Semi-arid Climate - Clay Mineralogy in a Geological Engineering Context

• Published in: Journal of geoscience education Vol. 55; no. 4; p. 295
• Main Authors: Harrison, Wendy J, Wendlandt, Richard F
• Format: Journal Article
• Language: English
• Published: Bellingham Taylor & Francis Ltd 01.09.2007
• Subjects: Accreditation; Case studies; Control Groups; Data collection; Engineering research; Engineers; Exercise; Geochemistry; Learning; Mineralogy; Opportunity; Problem Based Learning; Scanning electron microscopy; Teaching methods
• ISSN: 1089-9995; 2158-1428

The identification of clay mineral assemblages in soils provides a unique opportunity to demonstrate how basic principles of mineralogy, petrology, and geochemistry are applied to engineering design criteria in construction site preparation. Specifically, the laboratory exercise presented investigates the conditions leading to the formation of smectite in soils and the resulting construction risk due to soil expansion. Students examine soils developed on igneous, metamorphic, and sedimentary rocks near Golden, Colorado. The field locations are areas of suburban growth and several have expansive soil problems. This 2-3 week exercise accomplishes three objectives: First, existing skills in XRD analysis are reinforced and new skills are developed by introducing students to concepts of particle size separation, particle orientation, and sequential analysis steps which are standard practices in clay characterization. Second, lecture material on the geochemistry of weathering of different rock types is applied through a local, practical example. Third, the role of petrologic characterization in site engineering is demonstrated. Students use Atterberg Limits measurements in conjunction with soil mineralogy to assess swelling potential and to design soil treatment needs for each building site. Qualitative and quantitative assessment and evaluation of student learning using a pilot class and two control groups was undertaken using written final reports and final exam questions. Written reports demonstrate proficiency in several lower and higher level concepts encompassed in ABET, Inc. Engineering Criterion 3, however, the use of traditional end-of-semester exams did not capture the knowledge gained by the students completing this problem-based learning exercise. [PUBLICATION ABSTRACT]