Preliminary results from tests using sublevel caving with 40 m sublevel height at LKAB

Abstract

LKAB operates two underground iron ore mines located in the northern part of Sweden, both using sublevel caving as the mining method. Common sublevel heights vary between 25-30 m. Tests with 40 m sublevel height is ongoing in a fairly small orebody called Konsuln located close to the main Kiruna orebody. LKAB has developed three sublevels (436, 486 and 536 m) in Konsuln to test sublevel caving with 40 and 50 m sublevel height. The objective with these tests is to assess the applicability of large sublevel heights in some of the LKAB future production areas. The production started in March 2021 at level 436, and it is currently the only level in production. Development work with the ramp started in 2018. Production drilling is ongoing at the second level (486 m) with 50 m sublevel height and drifting is being completed at the third level (50 m sublevel height). About 0.8 Mt has been produced so far from blasted rings at level 436. Preparations necessary for planning and for the assessment of the performance of these large sublevel heights includes:1. Measurements of blasthole and raise hole deviations. Installation and detection of smart markers.3. Measurements of iron grades in selected blastholes. 4. Opening blast tests. 5. Scanning of eventual open cavities. 6. Blast performance assessment.Follow up of the performance of the rings involves collection of data from loaded buckets, recovered markers, blast function (vibrations) and visual inspections as well as laser scanning when appropriate. This paper describes the preparations and the results achieved so far for blasted rings using 40 m sublevel height.