LKAB Introduces Large Hole Diameter Stoping at the Fabian Mine

The Fabian ore body near Malmberget, Sweden, has an ore reserve of 5 Mt of predominately low grade iron ore, containing 40-55% Fe. Mining began in 1971 with a new method called slot block caving. About 2 Mt were mined, but poor fragmentation resulted in too much secondary blasting. This decreased mucking efficiency to such an extent that the method was abandoned after only 40% of the ore volume had been mined. At this stage a large stope (180 x 30 x 100 m) had been excavated. Although the exposed area was quite large, no caving action occurred in the hanging wall or in the ceiling. LKAB decided in 1977 to introduce sublevel stoping using 105-mm-diam holes. This was the first time large diameter holes were used underground in Sweden. The method had been evaluated in collaboration with the University of Luleå (LuH), the Swedish Detonic Research Foundation (SveDeFo), and the Swedish Mining Research Foundation.