Mining Between Graphite Schist and Variable Quality Backfill

This paper describes a case study of early mining at the Kittilä Mine and the recovery of the first sill pillars in the Roura and Suuri orebodies. Mining of the first secondary stopes in Roura led to local instability. Both footwall and hanging wall contacts consisted of tightly jointed rock mass with graphite on undulating surfaces. Recovery of the affected area and monitoring results are presented herein. Different approaches were required for sill pillar recovery given the different geometries of the orebodies, and stopes with variable quality backfill. Backfilled stopes were classified according to observed quality, and the mining sequence was modified based on the results. 40-m high Roura stopes were mined from overcuts developed through backfill; 25-m high Suuri stopes were mostly mined with uppers from the undercut. Only the last stope in the 150-m long Roura sill experienced instability, and one secondary stope in Suuri was deemed unsafe and abandoned. Overall, the sill mining in poor backfill conditions was a success.