Mechanical properties of unbound granular materials reinforced with nanosilica

The development of new technologies for soil improvement has been a hot research topic in the fields of geological engineering, geotechnical engineering, and road engineering. Nanomaterials have been proven to offer significant advantages in the field of geotechnical material enhancement due to their unique structures and excellent properties. The effect of nanosilica amount on the stress-strain behavior, elastic modulus, shear strength, and shear parameters of unbound granular materials was investigated, and its potential enhancement mechanism was discussed in this research. Treated samples with nanosilica contents (by weight) of 0,1%, 2%, 3%, 3.5%, 4%, and 4.5% were prepared and rigorously examined through unconsolidated undrained (UU) triaxial tests under different confining pressures. Also, the intrinsic mechanism and variations in the microstructure of the specimens were investigated by the computed tomography (CT) and scanning electronic microscope (SEM). Testing results showed that with the addition of more nanosilica, the elastic modulus and shear strength of the specimens increased and the ductility decreased. The apparent cohesion of the treated specimens increased approximately linearly and had almost as little effect on the internal friction angle. The maximum improvement rate was obtained at 3.5% of nanosilica content. The CT and SEM scanning results indicated that the control specimen has a higher void ratio than the treated specimens, and the filling and nucleation effects of nanomaterials may be the intrinsic mechanism to improve the mechanical properties of unbound particulate materials. The experimental results contribute to enriching the application of nanomaterials in geotechnical engineering, guiding the optimization of mechanical properties of unbound granular materials.