Pilot-scale modeling of colloidal silica delivery to liquefiable sands

Passive site stabilization is a developing technology for the in situ mitigation of the risk of liquefaction without surface disruption. It involves the injection of stabilizing materials into liquefiable saturated sand. In this study, a pilot-scale facility (243 cm by 366 cm in plan×122 cm deep) was used to inject a dilute colloidal silica stabilizer into liquefiable sand specimens. The grout advancement was monitored in real time using electrical conductivity cells embedded in the specimens. Injection rates ranging from 65 to 9000 ml/min/well were used to investigate the optimal rate of grout delivery. In tests with low injection rates, the delivery performance was low due to sinking, while at higher injection rates, sinking was less noticeable. After the treatment, the degree of grout penetration was evaluated by excavating the model. The in situ unconfined compressive strength was measured using a pocket penetrometer, and soil blocks were excavated for additional unconfined compressive testing. Moreover, the 3-D flood simulator, UTCHEM, was utilized to simulate the experimental results and to predict the injection rates for adequate stabilizer delivery. The results of the strength testing demonstrated that as little as 1% by weight of the colloidal silica provides a significant improvement in strength after a month of curing. The study also revealed the feasibility of delivering colloidal silica to liquefiable sands by implementing a large-scale treatment.