Stabilization of saturated silty sand by colloidal silica: compressive and cyclic strength and shear wave velocity

Passive stabilization of the saturated loose sandy landfills especially in developed regions was researched recent decades. Aiming to passive stabilization and keeping the soil structure undisturbed, colloidal silica was applied as a suitable stabilizer because of the controllable properties such as low viscosity and gelling time. Due to the existence fine content in natural soil layers and its effect on the mechanical behavior of the soil media, it is necessary to study the influence of silty sand. Bender element test as a nondestructive test was conducted on the grouted samples with 0, 10, 20, and 30% silt fraction. Three different colloidal silica were injected to study the effect of different chemical condition on the results. All samples after small strain tests were loaded uniaxially under the unconfined condition to evaluate the cohesion of the samples. A series of selected samples were prepared again, and the undrained cyclic resistance was measured. All results showed that the samples with 10% fine content have a greater value of shear strength parameter as shear wave velocity at 28 days curing time. Also, cyclic strength was dramatically higher than ungrouted samples. However, after 14 days curing time, there was no clear difference while the fine content change. As a result, comparison of the data shows the shear wave velocity is a suitable index to evaluate the degree of soil improvement the grouted silty sand at the site.