The effect of diatom content on the physical, electrical, and mechanical properties of soils

Biological-formed fossilized diatom sediments have unique physical, electrical, and mechanical properties due to the shape, internal open porosity, and brittleness of the individual particles. The presence of diatoms strongly influences the overall behavior of soils. However, engineers and researchers find this influence challenging to quantify because measuring fossilized diatom content is elusive. This paper uses simple physical, electromagnetic, and mechanical engineering measurements to characterize the response of the artificial soils prepared with known amounts of fossilized diatoms under different pore-chemistry fluid and mechanical environments. Soils with high fossilized diatom content tend to retain high quantities of water even under high NaCl-concentration pore fluid. This response results from the internal porosity and is not a function of electrical forces on the particle surface. Furthermore, internal porosity governs electrical and mechanical properties under different pore fluid environments. Despite having elevated Liquid Limits, soils with high fossilized diatoms content do not deform while drying and changing pore fluid salt concentration. However, fossilized diatoms are brittle and offer high compressibility and low particle crushing stress (around 2–4 MPa). Our results show that simple physical and index tests can help assess the effect of fossilized diatoms’ in soils, and provide a framework to predict the engineering properties of natural soils containing a wide range of fossilized diatoms even when diatom content cannot be precisely measured.