THE ASBESTOS HILL - IMORDENHAM STORY - The Open-Pit Mine at Asbestos Hill
CIM Bulletin, Vol. 69, No. 775, 1976
Romeo Roussin, Mining Superintendent, Asbestos Hill Mine, Putuniq, Nouveau Quebec
The yearly production from the Asbestos Hill pit is 1,550,-000 tons of asbestos ore, with a yield varying between 18 and 20%. The orebody was exposed at the top of a hill, and initial production started without having to remove any overburden. The projected ratio of barren rock to ore, based on the present orebody, was 2 to 1. However, as it was necessary to push back the upper benches, this ratio has changed to 3 to 1.
The final pit will be 2,300 feet long by 1,000 feet at the longest and widest points. The final depth will be 680 ft. A pit slope stability study was carried out and an average wall angle of 60-70 degrees must be maintained. Pre-shearing of final pit limits will produce good wall stability.
Permanent access ramps will be 60 ft wide, with an 8% maximum grade.
Geological conditions and the low rock temperature are the major causes of the operation's drilling and blasting problems.