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https://www.nationalacademies.org/trb/events

Phase III Wickiup Junction: Diatomaceous Soil Numerical Modeling to Support Design, Performance, and Feasibility

Diatomaceous soils exist at many Oregon Department of Transportation (ODOT) projects in Oregon, including the Wickiup Junction overpass site. Construction challenges have been encountered for ODOT projects on and in diatomaceous soils, including pile freeze, overlength piles, and excessive settlement. Ongoing Wickiup Junction embankment monitoring indicates that these embankments are undergoing continuous settlement at about 1.75 inches per year. Recently, a consultant’s feasibility study estimated that settlement mitigation for future overpass construction will cost $47M to $63M. This high mitigation cost is attributable to extensive deposits of soft and compressible diatomaceous soils that underlay the site. Considering that diatomaceous soils are non-standard geomaterials, limited literature, standards, or case histories exist to guide design and construction in these materials. However, this Wickiup Junction location may provide a prime translational research opportunity to improve engineering practice through development of a case history report with associated design charts for diatomaceous soils. This highly applied research proposal will investigate the recently released design options at Wickiup Junction using advanced soil numerical modeling as a case study for design in diatomaceous material. This work will build on previous ODOT diatomaceous soil research to develop design tools that can be applied for construction in and on these deposits. Specific objectives include: (1) develop settlement model of the Wickiup Junction Overpass, and (2) develop design charts for diatomaceous soils.