Abstract: The adoption of pillarless sublevel caving with high sublevel and large drive interval is a world development orientation. To coordinate with Kun Steel's 4 million t/a project construction of mining, mineral processing and piping, new technology of pillarless sublevel mining with 20m high sublevels and 20m drive intervals was investigated. In light of the large drive interval, large-spaced drive drawing theory was adopted, radically changing the arrangement based on traditional theory of elliptical body ejection and realizing an arrangement fully tangential to ejected elliptical body. The best structural parameter combination of independent advance of ore breaking, blasthole row interval and bottom-hole interval were investigated through industrial test, controlling the large segmentation rate within 3% and ore dilution rate in drawing within about 5% and comprehensive ore recovery above 85%. The successful test of 20m x 20m non-pillar sublevel caving method in Dahongshan Iron Mine has greatly raised the mine capacity and reduced the mining cost, drawing China's mining technology level much nearer to that of foreign advanced mining technology (30m sublevel height).

Key words: Large spaced arrangement, Low dilution rate of ore drawing, Independent advance of ore breaking