Experiment study on normalized compression behaviour of marine diatomaceous soil considering microstructure of biogenic silica

Abstract

There are many sites in the world where diatom microfossils have been detected, but very little is known about their effect on sediment geotechnical properties. Diatomaceous soils (herein called “biogenic silica soils”) are usually composed by a mix of sand, fine-grained clay and diatom (and, or radiolarian). This paper presents an experimental investigation on the compression behaviour of biogenic silica-kaolin (BSi-K) clay mixtures and natural marine diatomaceous soils. The results show that the BSi composition dominates the compression when the BSi content is higher than 50%. The microstructure of biogenic silica frustules is first characterized and a skeletal void volume model (BSi-SVV model) is proposed. By using this model, the addition water in biogenic silica frustules can be quantitatively evaluated, which is up to 92.6% as the BSi content is 78%. It can be explained as the cause of high natural water content and low plasticity of diatomaceous soils. By introducing the effective void ratio, the compression curves can be normalized; furthermore, a new intrinsic compression line (BSi-ICL) suitable for BSi-K clay mixtures is developed based on the intrinsic compressibility concept of Burland (1990). It is considered as an extension of Burland's ICL. Finally, the effect of initial water content on the normalized compression behaviour is investigated. The findings in this study can provide a deeper insight into the geotechnical properties of marine diatomaceous soils.