Case Histories on The Applications of Colloidal Silica for Permeation Grouting-Paper

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The paper reviews colloidal silica (CS) as a permeation grout for improving soil and rock strength and reducing permeability, particularly where conventional or microfine cement cannot penetrate. CS is a low-viscosity aqueous grout (about 3–5 mPa·s) that forms a permanent gel, bonds soil particles, and can be used across a broad temperature range. Its lower alkalinity and long-term stability distinguish it from sodium silicate grouts.<br /><br />Five case histories illustrate its applications: consolidating cohesionless soils during sewer construction in Northern Italy; controlling groundwater in weathered granitic rock at California’s Arrowhead Tunnel; reducing water ingress at the White River/Lower Pogues Tunnel; stabilizing sandy soil for an elevator-pit excavation; and supporting sheet-pile installation for a cofferdam in the UAE. Reported benefits included improved soil cohesion and stiffness, reduced settlement, successful excavation, and groundwater control where cement grouts had inadequate penetration.<br /><br />The authors also compare CS with sodium silicate using a numerical model for grouting fine sand. In the modeled scenario, CS’s lower viscosity allowed a larger injection radius and fewer injection points. Although CS grouting itself took longer and cost more, the reduced drilling requirements lowered estimated total costs to about half those of sodium silicate.<br /><br />Overall, the case histories and modeling indicate that colloidal silica is a versatile option for permeation grouting in fine soils and fractured or weathered rock, provided injection pressures and flow rates are carefully controlled.

Keywords

colloidal silica

permeation grouting

soil stabilization

rock strengthening

low viscosity grout

groundwater control

fine sand grouting

sodium silicate comparison

case histories

grout penetration