Effect of diatom inclusion on physical property identification of soft clay

PurposeSediments containing diatom microfossils extensively deposit in lacustrine and marine environments. The silty and porous diatoms, unlike common rock-forming minerals, are of strong water adsorption, whose introduction makes the soil an intractable problem. This study discussed the transmutation of clayey soils with diatom inclusions from physical and microstructural perspectives.Materials and methodsMineralogy and microstructure of kaolin and diatomite were first analyzed, and their mixture was used to simulate the natural sediments. The consistency limit, specific surface, and activity of the mixtures with different diatom proportions were achieved by laboratory experiments, and those from literatures were also collected. Thereinafter, the evolution of physical property and characterization by diatom incorporation was analyzed to reveal the diatom inclusion effect.Results and discussionWith enrichment of diatom microfossils within the silt fraction, the consistency limits, soil activity, and specific surface area significantly diverge from the traditional cognition of clay mineral and particle size-dependent behavior. Microstructure reveals that the physicochemical and structural differences between diatoms and clay minerals underlie the paradoxical performance. The plasticity chart would be updated to classify the fine-grained soils with diatom inclusions by excluding the water stored by diatoms. A modified multi-phase and porosity-division model was proposed to identify the water retention of diatom in volume and mass to characterize the plasticity nature of this sediment.ConclusionThe evolution of soil properties after diatom intervention was clarified. New porosity division and "real plasticity" identification system helps to establish an accurate understanding of diatomaceous soils.