First Advisor

Arash Khosravifar

Term of Graduation

Summer 2020

Date of Publication


Document Type


Degree Name

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


Civil and Environmental Engineering




Shear strength of soils -- Testing, Soil liquefaction -- Pacific Northwest, Plasticity, Geotechnical engineering



Physical Description

1 online resource (ix, 191 pages)


A magnitude 9 Cascadia Subduction Zone earthquake is expected to trigger widespread liquefaction in loose material in Oregon. The geotechnical engineering studies have determined that the Willamette Silts may be susceptible to liquefaction or cyclic softening, as their plasticity indices ranges between non-plastic to low plasticity. While the majority of past studies have focused on liquefaction of sand and cyclic behavior of clays, there is not enough data on the cyclic response behavior of silty soils and the liquefaction susceptibility of these soils. A research focus in the geotechnical engineering program at Portland State University revolves around is performing cyclic tests on samples obtained from regional silts to fill the gap in data, in an effort to better characterize the liquefaction susceptibility of non-plastic to low plasticity silts. The primary goal of this thesis is to study the behavior of undrained cyclic shear resistance of low plastic fine-grained soils that were extracted from Beaverton, OR. The constant volume direct simple shear test device made by GeoComp is used to test the soil samples. The critical challenge in this project was to prepare close-to-identical remolded specimens to be able to evaluate intricate differences in the cyclic behavior of silts under different loading conditions. The thesis will present the cyclic shear resistance of laboratory prepared samples and the adopted procedures to prepare identical slurry samples.


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