méthode d'exploitation par sous-cavage-remblais

OBS: [In] base metal mines (...) a large proportion of the ore reserves is found in pillars left between previously mined stopes. These pillars are usually mined using the undercut-and-fill method which is especially suited to unstable ground conditions. Starting at the top of the mining zone the ore is removed in horizontal slices and replaced by backfill to sustain the walls of the adjacent stopes. A wooden mat braced by posts is used to support the backfill so that the ore underneath can be removed. (...) In one mine, the conventional undercut-and-fill technique was modified by suspending the wooden mat on rock bolts anchored to the crown pillar, rather than supporting it on posts.