Portland State University. Department of Civil & Environmental Engineering
Term of Graduation
Date of Publication
Master of Science (M.S.) in Civil & Environmental Engineering
Civil and Environmental Engineering
Diatomaceous earth, Soils -- Analysis, Diatoms, Scanning electron microscopy
1 online resource (x, 128 pages)
Diatoms are single-celled organisms of various shapes and sizes typically found in aquatic environments. When diatoms die, the organic material decomposes, and the outer skeletons (i.e., frustules) settle and accumulate as sedimentary deposits. These soils, called diatomaceous soils, exhibit nontraditional behavior since the diatom particles are typically hollow skeletons composed of amorphous silica with intricately patterned and abrasive surfaces. Recent studies have shown that diatomaceous soils are challenging geomaterials since even a small percentage of diatom particles will notably affect engineering behavior. Furthermore, laboratory studies on diatomaceous soil mixtures have demonstrated that many engineering soil properties depend on the percentage of diatom particles. For example, liquid limit and plastic limit increase as the percentage of diatom particles increases. Although the percentage of diatom particles relates to geotechnical properties, there are currently few published correlations to quantify this relationship. This research has two objectives: (1) to develop a method to characterize diatom particle percentage for natural diatomaceous soils; and (2) to relate these percentages to physical properties. The soils for this project were sampled from southern and central Oregon in Pinecone Way, Chiloquin and Wickiup Junction, La Pine, and imaged using scanning electron microscopy (SEM) to obtain high resolution images. These images were then analyzed using quantitative stereology to estimate diatom particle percentages. The sample from the Pinecone Way field site had approximately 92% diatom content, while the sample from the Wickiup Junction field site had about 88% diatom content. These percentages are compared to measured soil properties to evaluate the relationship for these natural diatomaceous soils. The sample from the Pinecone Way field site had liquid and plastic limit values that agreed with previously published trends for high diatom content mixtures. Liquid limit and plastic limit data were not available for the Wikiup Junction site.
© 2021 Ariadna Covarrubias Ornelas
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Covarrubias Ornelas, Ariadna, "Using Quantitative Stereology on High Resolution SEM Images to Estimate Diatom Percentages" (2021). Dissertations and Theses. Paper 5781.