A laboratory and in-situ investigation of silica colloid injection on reducing liquefaction potential in young coastal sediments in the south of the Caspian Sea

In this study, soil samples with different weight percentages of silica colloids were subjected to uniaxial compression strength (UCS) tests in a parking lot in Anzali port (northern Iran) to estimate the suitable amount of these colloids to prevent soil liquefaction (10 wt.%). Next, by performing triaxial cyclic tests, the behavior of native sand and the one stabilized with optimal silica colloidal content (10 wt.%) was studied to ensure the occurrence of liquefaction with this content. Afterward, the soil of the study site was improved through a straightforward method, which includes driving screened pipes and injecting silica nanocolloids into the soil by these pipes with appropriate injection pressure. Key parameters in this method include accurate determination of injection pressure, gelation time, grain-size distribution of soil, and proper distribution of silica colloids at the site. In the next step, the effectiveness of the proposed improvement method was assessed by performing standard penetration tests and measuring the hydraulic conductivity. Overall, the results revealed that the proposed improvement method significantly enhanced the standard penetration number, and the formation of colloidal silica gel lowered the hydraulic conductivity of the study site. For instance, the average permeability in the first layer of unstabilized soil was 2.1 × 10-2 cm/s, which reaches 1.6 × 10-8 cm/s by performing the grouting operation. Finally, the relationship quF = 0.68 × quL was obtained between laboratory and field UCS values of the study site by sampling the soil stabilized in situ and performing UCS tests on them.