Interest has been increasing in studying diatomaceous earth stemming from the challenges posed by their presence in various engineering projects, such as the US 97 at Wickiup Junction project in Oregon. At Wickiup Junction, an overpass crossing was being built to replace the last at-grade rail crossing on US 97, and the previously undetected presence of diatomaceous earth caused massive and uneven settlement under the earth embankments. This report presents the results of geotechnical laboratory tests conducted on diatomaceous earth from Northern California, including grain-size distribution, Atterberg limits, specific gravity, direct shear, and 1-D consolidation. The soil’s performance under cyclic stress was evaluated through a series of cyclic triaxial shear tests. The findings reveal the unique and non-textbook nature of diatomaceous earth properties.
