ACT was awarded the contract for the installation of a single row grout curtain to depths of 150 feet within the granitic foundation rock. The grout curtain in conjunction with a plastic cutoff wall forms a system designed to prevent water seepage through the foundation of the Dike where open pit mining occurs.
The project site is located in the Northwest Territories in Canada and is situated in the Arctic Circle, approximately 230 KM (140 Miles) North of Yellowknife. The project was subjected to severe winter conditions with temperatures as low as –50° C (-58° F). Operating in these severe winter conditions required a custom water heating/distribution plant, a custom built automated grout batch plant, and custom built mobile grout header stations.
Work included drilling grout holes through the plastic cutoff wall and into the underlying rock. In most areas, the drilling was performed prior to the installation of the plastic cutoff wall and included installation of overburden casing through the rockfill dike, followed by percussion drilling the rock formation below. Grout holes were water tested to determine hydraulic conductivity of the formation prior to grouting as well as post grout water testing of random holes to determine post grouted hydraulic conductivity of the grouted areas. Pressure grouting of the foundation was performed using balanced stable grout mixes.
Real time electronic monitoring and recording of actual grout flows and pressures was utilized to analyze the grouting program. Flow and pressure time trend plots were monitored to establish effective refusal of each grouting operation.