Innovative Grouting Techniques for Installation of a Seepage Barrier at Barrage des Quinze Dam (Quebec, Canada)-Paper

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The Barrage des Quinze is a 19-section concrete dam on Quebec’s Outaouais River. During rehabilitation, conventional cement grouting reduced seepage in 14 sections but failed in five, where high-velocity water washed grout from large openings beneath the dam. Construction also temporarily reduced structural stability, limiting allowable grouting pressures.<br /><br />The team developed a staged approach to seal the five problematic sections: first cut off major flows, then seal the dam–bedrock contact, and finally complete a deeper grout curtain in the underlying rock. The work included borehole-camera inspections, water-pressure testing, grout-mix trials, and close monitoring of injection volumes and pressures. Because of the dam’s stability limits, injections were controlled to avoid excessive uplift.<br /><br />The key innovation was adding sodium silicate to a balanced, stable high-mobility cement grout at the injection point. Its rapid set prevented washout and stopped high-flow leakage. This technique proved more effective than anticipated, so planned low-mobility and polyurethane grouts were not needed for the barrier. Barrier holes were treated in stages—grouting the upper section first, then redrilling and grouting deeper—to improve pressure control and sealing. A subsequent curtain-grouting stage achieved closure below five Lugeons.<br /><br />The project also required heated enclosures, equipment, and water to maintain grout performance during northern Quebec winter conditions, with temperatures reaching −40°C. In total, 157 holes were drilled, inspected, and grouted from January to March. The staged barrier-and-curtain method successfully reduced underseepage and restored contact between the dam and its foundation, completing the work on schedule for spring flow management.

Keywords

Barrage des Quinze

concrete dam rehabilitation

Outaouais River

seepage control

grouting

sodium silicate

staged barrier method

grout curtain

dam foundation sealing

winter construction