Justification of drill and blast pattern designs for ore treatment before in-situ leaching

Abstract

The article discusses drill and blast pattern designs for ore treatment before in-situ leaching (ISL) in ore bodies of complex structure with a view to ensuring ecological safety, enhanced ISL efficiency, as well as balanced subsoil protection and management. This is achievable using cut-and-fill method with cemented backfill of different composition and strength, as well as with other geotechnical methods. It is shown that ISL of metals from solid ore requires high-quality preparation of large volume blocks, associated with blasting of tens of tones of explosives at a time. Rock fragmentation by blasting is improved through the higher powder factor to 2.9–3.3 kg/m3, as well as through accumulation of rocks with a degree of fragmentation not less than Kf = 1.2–1.3 in a limited space at the bottom of a stope. A case study of the concurrent application of a conventional mining technology and ISL technology in the Michurin deposit, on level 26–21 m, at the ISL block width of 20 m and shrinkage height of 35 to 50 m has proved the required stability of roof spans, without any falls of oversizes or off-standard sizes to ISL ore blocks. The recommendations for the design approaches to ISL are developed and tested in mined-out stopes in test block 5-86 and in pilot production blocks 5-84-86, 5-88-90 and 1-75-79.