Improving the geotechnical properties of soft clay with nano-silica particles

This paper reports on an investigation into the effect of using nano-silica particles to improve the mechanical properties of clayey soil with low and high liquid limits. The engineering properties studied included Atterberg limits, maximum dry unit weight, optimum moisture content, California bearing ratio, consolidation and unconfined compressive strength. Nano-silica to soil ratios of 0·5, 0·7 and 1·0% were used. Both the Atterberg limits and California bearing ratio values improved with increasing nano-silica content. Increasing ratios led to a reduction in the plasticity index and an increase in the shrinkage limit. The reduction in soil settlement was attributed to a viscous gel in the soil–additive interaction, which resulted in an increase in the pre-consolidation stress of the stabilised soil. The test results showed that the viscous gel caused an increase in initial pre-consolidation stress of 70 kN/m 2 for a soft clay soil to 300 kN/m 2 for a soil stabilised with 0·7% nano-silica. Undrained compressive strength also increased by up to 56%. An increase in nano-silica content led to a reduction in failure strain but an increase in the elastic modulus of soils. Based on the results, it can be concluded that the addition of nano-silica improves the mechanical properties of clay significantly.