Preliminary Evaluation of Colloidal Silica Transport Mechanisms for Passive Site Remediation of Liquefiable Soils

Drexel University, Philadelphia PA

Investigators

Abstract

CMS-0219987, Patricia M. Gallagher, Drexel University "Preliminary Evaluation of Colloidal Silica Transport Mechanisms for Passive Site Stabilization of Liquefiable Soils" This project involves an exploratory evaluation of colloidal silica transport mechanisms to stabilize liquefiable soil formations. The results will be used to support development of a non-disruptive technique for ground improvement. "Passive site remediation" is a new concept for non-disruptive mitigation of liquefaction risk at developed sites susceptible to liquefaction. The concept is to slowly inject a stabilizing material at the up-gradient edge of a site, and deliver the stabilizer to the liquefiable area using the groundwater flow. The focus is on the ability to deliver colloidal silica solutions uniformly into liquefiable soil deposits, with subsequent gelation to mitigate the liquefaction susceptibility. The main goals of the research are: (1) to determine if colloidal silica grout can be transported through a column of liquefiable soils in an adequate concentration to stabilize the sand; (2) to determine if the grout will gel along the entire length of the column after delivery; and (3) to understand the mechanisms of colloidal silica transport through liquefiable sands. The research involves laboratory experiments consisting of short and long column tests to identify the variables that influence colloidal silica grout transport in liquefiable soils. The parameters to be considered include the geochemical and physical factors thought to affect grout transport most strongly, such as pH, ionic strength of the grout solution, flow velocity, and pore size of the sand formation. The effects on the transport of gelling fluids with variable density and variable viscosity will also be considered. This research will set the stage for future development of implementation technologies and field testing of passive site remediation. The research results will be widely disseminated among researchers and practitioners in the areas of geotechnical earthquake engineering, ground improvement, grouting, and environmental remediation. Passive site remediation techniques could have broad application for developed sites susceptible to liquefaction, where traditional ground improvement methods are difficult or impossible to implement. These techniques could also have application to urban areas where subsurface contamination is difficult to remediate.