Geotechnical Properties of Nanoscale Fumed Silica-based Transparent Clay

The mechanical properties of transparent soil influence its reliability in visualization-based model tests. This paper investigates the static and dynamic behavior of nanoscale fumed silica under water-based pore fluid conditions. Initially, index tests suggested that its Atterberg limits and compressibility in water-based fluid exhibited a degree of similarity to highly organic clays. Additionally, monotonic and cyclic shear tests were conducted to compare its geomechanical properties with highly organic soils. Microscopic analyses were then conducted using scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR) under various pore fluids. Results indicated that the critical state friction angle of fumed silica, obtained from conventional triaxial compression (CTC) tests, was 40.6°, comparable to many highly organic soils. It also exhibited a high peak friction angle and low cohesion, reinforcing its behavioral similarities to these soils. The normalized undrained strength ratio matched that of silt. The cyclic behavior corresponded with highly plastic soils, while the shear modulus decay curves were comparable to those of highly organic soils. However, the damping ratio remained lower. SEM and FTIR verified that the concentrated surface functional groups may be the reason for the high friction angle characteristics of fumed silica.