First Advisor

Trevor D. Smith

Date of Award


Document Type


Degree Name

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


Civil and Environmental Engineering




Silt -- Oregon -- Portland -- Databases, Silt – Research, Portland (Or.) Bureau of Environmental Services




Willamette Valley silt deposits from historical catastrophic flood events present a difficult problem for subsurface engineers practicing in the Portland, Oregon area. Silts exhibit behavior of two very well-documented soil types, but publications containing mechanical properties for silts are scant, especially for local silts. Thus, the need for links between real Portland site investigation data and silt properties is high. To further exemplify the need for documented knowledge of local silts, this project reveals the evolving state of practice to incorporate more Pacific Northwest seismic analyses in preparation for a subduction zone earthquake. The geotechnical Portland BES databases contain thousands of private sector (PrS) and public sector (PbS) geotechnical documents from sites in the Portland area. The PrS database includes approximately 7,000 geotechnical documents for PrS projects dating primarily from the mid 1900’s to 2009 for a range of project types. A statistically significant random sample of 1,500 documents from the PrS database was organized and analyzed. The approximate 1,000 documents in the PbS database containing boring logs can be linked to location through a pre-existing GIS layer. The statistically significant sample from the PrS database and the GIS layer from the PbS database were compared spatially to reveal clusters of documented geotechnical projects. An isolated cluster of 80 full geotechnical reports in the Downtown, Portland area from reputable practitioners was examined for standard penetration blow counts, equipment information, groundwater table depths, soil descriptions, unit weights, drill dates, and moisture contents to capture a range of correlated peak effective friction angles for different compositions of silt. The project types and report contents from the PrS database were analyzed in the Downtown area, and conclusions were made on the percentages of project types and apparent chronological trends in report content.



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A research project report submitted in partial fulfillment of the requirement for the degree of Master of Science in Civil and Environmental Engineering.

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