| The low-viscosity stabilizer, colloidal silica, is extensively used as a grouting material in the construction of grout curtains. It has low viscosity and is non-toxic, which is suitable for injection to stabilize fine-grained soils. It is also applied as a stabilizer in the in-situ treatment of hazardous waste. Once the colloidal silica solution is injected into contaminated soil, it moves through the pores inside the soil matrix, initiating the stabilization process. The viscosity of the colloidal silica mixture increases while it moves until solidifications. This process is called gelation and results in the creation of a gel barrier around contaminated soil particles, causing a substantial reduction of fluid flow in the soil, this will minimize the movement of water and hence movement of contaminants through the gel mass.In this research, the stabilization process of chromium contaminated soils using colloidal silica were investigated. The transport of colloidal silica during injection was simulated at the microscopic level to further understand the gelation process. Diffusion of chromium through colloidal silica gel was modeled to evaluate the effectiveness of the technology. A new optical method to estimate the diffusion coefficient of chromium in gel was purposed. The diffusion coefficient obtained using the above optical method was used to evaluate the long term effectiveness of colloidal silica grouting technology.The movement of colloidal silica during the injection was modeled using the change in gel viscosity with time. The simulation showed that during the grouting process, solidification starts at the soil surface and expands to fill the void space within 1.2 hours. The different soil geometries resulted in the different velocity contours and different colloidal silica solidification patterns. The greater the ellipsoid axial ratio of soil resulted in faster solidification. (Abstract shortened by UMI.)... |
