Optimal mining sequences in very steep ore bodies

The planning of underground mining sequences represents an important aspect of the mining operation. The analysis of mining sequences actually in use for very steep orebodies has demonstrated that they are not always optimal considering ground control and the number of slopes simultaneously in extra ction. These sequences are conducive to the creation in the rockmass of sev eral stressed zones caused by pillar effects. The case study of lac Shortt mine showed that the sequences of exploitation currently in use are not ade quate especially in the case of a high state of the natural constraints. In deed, the mine had serious problems with ground control (rock bursts and co llapse of walls). These collapses were responsible for excessive dilution a nd significant losses of mining reserves. The two new sequences suggested a im for the best redistribution of exploitation constraints in order to elim inate creation of pillar effects. Moreover, they allow a higher number of s topes to be extracted simultaneously in the opinion of the authors, the seq uences suggested could substantially improve the stability of working areas and, thereafter technical and economical performances of the underground o perations.