Justification of process flows and designs for mining blind ore bodies in the vicinity of mined-out voids

Abstract

The trending deep-level mining governs substantial alteration of geomechanical situation in mines. The key approach to the stress–strain behavior assessment in rock mass when predicting and preventing geodynamic events is the geomechanical analysis of the rock mass behavior in the course of mining. The rockburst-hazardous mining research can use such methods as microseismic investigation, acoustic micromeasurements, electrometry, deformation monitoring, etc. The authors have accomplished the stress–strain behavior assessment in rock mass during mining at rockburst-hazardous deposits of Tashtagol and Sheregesh. The process solutions on underground mining in high-stress rock mass are analyzed. The process flow charts are developed. Alternative stoping technologies are identified, and the design data of mining systems for blind ore bodies are justified. It is shown that safe and efficient mining of blind iron ore bodies in the vicinity of mined-out voids in rockburst-hazardous conditions is achievable using: room-and-pillar mining, with rooms arranged across the strike of an ore body, and with subsequent transition to sublevel caving with levels 70 m high and sublevels 25–30 m high; shrinkage stoping and bulk caving; cut-and-fill method with cemented backfill. It is found that in top-downward mining of blind ore bodies, the transition from the room-andpillar system to sublevel caving and cut-and-fill method ensures reduction in ore loss and dilution by 1.1–1.5 and 7.5–10 %, respectively.