The methodology of calculating the normative strength of backfill in the system of mining with sub-stage ore stripping in diamond-shaped chambers is considered. It is proposed to take as normative the largest design value of strength determined from the conditions of stability of the diamond-shaped chamber vault and stability of the complex in shape and structure inter-chamber pillar formed between the chambers.

The ore deposit developed by the Mayak mine consists of disseminated and slump ores. Solid ores are located below the bulk of disseminated ores in highly fragmented and crushed rocks with sharply reduced stability. The thickness of these rocks in the immediate roof varies from 0.3-0.6 to 4.7 m, in the soil - from 0.5 to 5.5 m. The dip angle of the deposit varies within 3-12°, increasing up to 25-30° in some places on the flanks. The depth of development is 200-260 meters.