Main Haulage Level

Project Background

LKAB’s Kiirunavaara mine is a large, underground, sub-level caving mine in the north of Sweden. In May 2020 a large magnitude seismic event (ML=3.3 / Mw=4,2) caused significant damage to the mine infrastructure over a large volume leading to the disruption of all mining activities in parts of the mine.

After this event, a project for rock safety was started with a subproject measures at main haulage level, of which this project is a part. The project aims to answer the questions "where, when, how" the main haulage level will be affected as a result of continued mining.

Itasca's Role

A mine-scale model was constructed to simulate the stress change at the main haulage level due to continued mining. Different evaluation criteria were analyzed, to find a threshold level for when damage occurs, which was then applied to the main haulage level. The results showed that ore pass group 30 is where the rock mass will first be exposed to stresses exceeding all set levels for the stress criteria.

A local model of an ore pass group was analyzed to study stress change in the infrastructure in more detail. The local model includes the ore pass group and all adjacent infrastructure. Stresses from the mine scale model were retrieved for each year and used in the local model to simulate the stress changes due to mining.

Results Summary

The results for the local model identified the areas that are affected (first) by the stress change due to mining. Different parts reacts differently, in general: stress increases mainly towards the ore; tensile stresses and increased yielding mainly further away from the ore. The results can be used to decide where and when extra measures should be put in, e.g., inspections and extra reinforcements.