ABSTRACT
Dynamic loads may cause liquefaction of the saturated sandy soil. The colloidal silica grouting is the most advanced and effective sand stabilization method. Higher permeability of the colloidal silica gives the method an advantage over other soil stabilization methods. Due to its water-like density and viscosity, the highly dispersive colloidal silica with the particle size less than 15 nm (up to 15-30 nm) is capable to penetrate into sands of various grain size. It forms gel in soil pores after being mixed with activator, thereby stabilizing the soil. The paper presents results of the study on gel time, permeability properties and dynamic strength of sand against concentration of the colloidal silica and sand density. It has been obtained that with increasing colloidal silica content and activator concentration, as well as with increasing temperature, the gel time significantly reduces. The defined and therefore recommended for use colloidal silica concentration ranges from 5% to 10%, which provides gel hardening within 10 days at the activator concentration of 1-2%. It has been found that dynamic strength of sand increases by 1.5-5 times when sand is grouted with minimum concentration of 5%. The performed study has shown that the colloidal silica concentration of 5% is sufficient for stabilizing the soil subjected to earthquakes of the intensity up to 9 (on the base of MSK-64 scale). The dependency of gel time on concentration resulted from the study can be applied in design practice. Due to its permeability, colloidal silica is a promising material for strengthening clayey or silty sand.
