Rheological Properties of Colloidal Silica Grout for Passive Stabilization Against Liquefaction

Abstract

Passive (site) stabilization is a novel technique for the mitigation of seismic liquefaction which uses low-pressure injection of colloidal silica in the pores of a granular soil. The applicability of colloidal silica as a grout relies on the control of its time-increasing viscosity. Current knowledge depicts silica type, percentage of silica by weight, pH, and salt (ion) normality as the controlling parameters of colloidal silica viscosity, whereas current practice requires case-specific viscosity measurements before in situ injection. This paper presents a set of viscosity measurements of widely different colloidal silica solutions which confirm literature findings and depict temperature as an additional controlling parameter. The wealth of these measurements enables a reliable statistical analysis, which leads to the proposal of a set of charts and equations for the approximate estimation of the time-increasing viscosity of colloidal silica solutions. This information is paramount for the design of the in situ injection process and its importance is demonstrated via indicative one-dimensional injection tests of colloidal silica in sand columns.