Perennialy frozen placers at depth of 10 to 30 m may be profitably mined by combining the opencast and underground mining procedures. According to this method, the placer is at first partially mined in opencasts, and then the underground mining is used to recover the rest of it.

The underground mining is carried out by means of systems of chambers with gravel rib pillars left or artificial backfills produced. The technique involving freezing of water is applied to construct artificial pillars. Overburden rocks are used as the stowing material. Underground gravels are recovered and transported to the washing site.

The opencast-underground technique is the most expedient for mining deep placers considering the problems of recultivation under the Arctic conditions.

You can access this article if you purchase or spend a download.