Muskrat Falls North Dam Grout Curtain with Gin Principle-PPT Presentation

PPT Presentation

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The Muskrat Falls North Dam grout curtain was installed as part of an 824 MW hydroelectric project on the lower Churchill River. Its goal was to seal fractures and faults beneath the dam and achieve final water-pressure test results of no more than 1 Lugeon.<br /><br />The bedrock is generally hard, crystalline granite gneiss with low hydraulic conductivity, though testing identified localized zones of high water take. A single stable grout mix was used throughout, supporting consistent comparison of grout takes. The mix had a water-cement ratio of 0.75, a viscosity of about 32.5 seconds, specific gravity of 1.64, and 1% bleed after two hours. High-early-strength cement and superplasticizer helped improve grout penetration and flow.<br /><br />Field trials calibrated the monitoring equipment, tested the mix under site conditions, and established pressure limits to avoid hydro-fracturing. The Grout Intensity Number (GIN) method regulated pressure and grout volume together, preventing excessive pressure and flow at the same time. Production work included staged drilling and grouting, automated monitoring, and regular quality checks of drilling and grout properties. During cold weather, superplasticizer dosage was adjusted to maintain the target viscosity, and the refusal hold time was shortened to reduce the risk of grout freezing in hoses.<br /><br />Grout takes generally decreased through successive hole orders, indicating that fractures were progressively being sealed. Final profile data guided additional drilling and treatment. Verification holes were cored in areas with the highest grout takes, and water-pressure testing recorded a final value of 1 Lugeon, meeting the design requirement.

Keywords

Muskrat Falls

grout curtain

hydroelectric project

lower Churchill River

water-pressure test

Lugeon

granite gneiss

GIN method

superplasticizer

hydraulic conductivity