Physical and Numerical Model of Colloidal Silica Injection for Passive Site Stabilization

Passive site stabilization is a new technology proposed for nondisruptive mitigation of liquefaction risk at developed sites susceptible to liquefaction. This technology is based on the concept of slow injection of stabilizing materials at the edge of a site and delivery of the stabilizer to the target location by using the natural or augmented groundwater flow. In this research, a box model was used to investigate the ability to uniformly deliver colloidal silica stabilizer to loose sands using low‐head injection and extraction wells. Five injection wells and two extraction wells were used to deliver stabilizer in a generally uniform pattern to the loose sand formation. Numerical modeling was used to identify the key parameters affecting stabilizer migration and to determine their effective values for the box experiment. In our modeling approach, the stabilizer is treated as a miscible fluid, the viscosity of which is a function of time and the concentration of stabilizer in the pore water. Inverse modeling techniques are employed to reproduce data from the laboratory experiment for the determination of soil and stabilizer properties. While the details of the stabilizer distribution were difficult to reproduce with the simplified conceptual model we used, the overall system behavior was well captured, providing confidence that numerical simulation is a useful tool for designing centrifuge model tests, pilot tests, and eventually field stabilizer‐injection projects.