Engineering Characterization and Cyclic Failure of Diatomaceous Earth

The increasing interest in studying diatomaceous earth stems from the challenges posed by their presence in various engineering projects, such as the US 97 at Wickiup Junction project in Oregon. Diatomaceous earth consists of fossilized remains of diatoms, which have a highly varied and interlocking shape, giving the impression of strength until the skeletons crush under excessive stress. The engineering properties and cyclic performance of diatomaceous earth are not well understood. This paper presents and discusses 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 required numbers of cycles to cause the cyclic failure of the diatomaceous earth sample under two confining pressures (103 and 52 kPa) were presented. The cyclic stress-strain responses of diatomaceous earth exhibit characteristics of cyclic softening, similar to behaviors of clay-like soils.