Date of Award
5-2026
Degree Type
Thesis
Degree Name
Master of Science - Geology
Department
Geology
First Advisor
Dr. Wesley Brown
Second Advisor
Dr. Julie Bloxson
Third Advisor
Dr. LaRell Nielson
Fourth Advisor
Dr. Robert Friedfeld
Abstract
This study investigates the geotechnical, geophysical, and mineralogical characteristics of soils derived from the Weches Formation in Nacogdoches County, East Texas, with emphasis on the relationships among electrical resistivity, moisture condition, compaction state, and mineralogical composition. The Weches Formation is well known for producing clay-rich, moisture-sensitive soils that pose challenges to subgrade performance because of their plasticity and swelling behavior. Representative soil samples were collected and subjected to laboratory testing, including particle size analysis, Atterberg limits, Standard Proctor compaction, free swell tests, electrical resistivity measurements, and X-ray diffraction (XRD) mineralogical analysis. The soils are predominantly fine-grained and clay-rich, with USCS classifications dominated by CL, ML, and MH and showing variable plasticity and swelling potential. XRD results indicate a mixed mineral assemblage dominated by quartz and clay minerals, principally smectite, kaolinite, and illite, with chlorite present in smaller but persistent amounts. Correlation analysis shows that quartz is negatively associated with the Atterberg limits and plasticity index, whereas kaolinite, chlorite, and total clay exhibit positive relationships with these engineering properties, confirming the importance of mineralogical composition in governing soil behavior. Electrical resistivity analysis shows that moisture content is the dominant control on resistivity, with increasing moisture producing lower resistivity values. Relative compaction provides an additional but weaker influence. A base regression model relating log-transformed resistivity to moisture content and relative compaction produced an adjusted R2 of 0.471. When mineralogical information was incorporated, chlorite provided the strongest improvement among the tested mineral variables, increasing the adjusted R2 to 0.566 and reducing the model error. This demonstrates that mineralogy contributes meaningful explanatory value, although its effect remains secondary to hydro-mechanical controls. Overall, the results show that electrical resistivity in Weches Formation soils is governed primarily by moisture condition, with additional influence from compaction and a measurable but secondary mineralogical effect. The study supports the use of electrical resistivity as a rapid and physically interpretable supplementary tool for evaluating expansive subgrade soils when integrated with conventional geotechnical and mineralogical characterization.
Repository Citation
Annobil, Samuel, "Integrated Geophysical, Geotechnical, and Mineralogical Characterization of Expansive Weches Formation Soils in East Texas: Implications for Infrastructure Design" (2026). Electronic Theses and Dissertations. 695.
https://scholarworks.sfasu.edu/etds/695
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