Compression behavior of marine diatomaceous soils: Effect of diatom content and microstructure

The marine diatomaceous deposits are frequently encountered in ocean engineering, including ocean drilling projects, subsea foundations and the marine resource recovery systems. The diatom microfossils significantly affect the physical and mechanical properties of diatomaceous soils, distinguishing them from soils without diatoms. Such properties are directly related to seabed mechanics, and consequently the stability and design of ocean engineering infrastructures. However, how diatoms control the soil compression behaviors and the underlying mechanisms remain poorly understood. This paper systematically examines the compression behaviors of diatomaceous soils through compression tests on artificially prepared diatom-kaolin mixtures, quantifying the impact of diatom content and stress levels. Mercury-intrusion porosimetry and scanning electron microscopy were conducted to trace the microstructural evolution of the soils with diatom addition and compressive loading. The results indicate that diatoms significantly contribute to high compressibility of diatomaceous soils. This phenomenon can be explained by microstructural evolution, where alterations in pore characteristics and the breakage of diatom particles play critical roles during compression. Low vertical stress induced minor microstructural changes, compressing both intra- and inter-aggregate pores. Higher vertical stress triggers brittle breakage of diatom’s hollow structure, leading to pronounced rearrangement of soil structure and pore distribution, and consequently elevated compressibility. This work enhances comprehension of the mechanical behaviors of marine diatomaceous soils.