First Advisor

Diane Moug

Term of Graduation

Spring 2021

Date of Publication

7-16-2021

Document Type

Thesis

Degree Name

Master of Science (M.S.) in Civil & Environmental Engineering

Department

Civil and Environmental Engineering

Language

English

Subjects

Diatomaceous earth, Soils -- Analysis, Diatoms, Scanning electron microscopy

DOI

10.15760/etd.7652

Physical Description

1 online resource (x, 128 pages)

Abstract

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.

Rights

© 2021 Ariadna Covarrubias Ornelas

In Copyright. URI: http://rightsstatements.org/vocab/InC/1.0/ This Item is protected by copyright and/or related rights. You are free to use this Item in any way that is permitted by the copyright and related rights legislation that applies to your use. For other uses you need to obtain permission from the rights-holder(s).

Persistent Identifier

https://archives.pdx.edu/ds/psu/36351

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