LKAB Develops New Mining Method Raise Caving
When mining depths in underground mines increase, so do the challenges. Rock stresses increase as mining moves to ever greater depth. A more complex
When mining depths in underground mines increase, so do the challenges. Rock stresses increase as mining moves to ever greater depth. A more complex geometry, in combination with rock-mechanical challenges, places demands on new, sustainable and innovative solutions for the mine of the future. And, underground, safety is paramount. Therefore, an entirely new method, raise caving, has been developed by Swedish state owned iron ore mining company LKAB in Kiruna. This is a major groundbreaking step towards a safer, more efficient mine. The greater mining depth has necessitated the development of the new method, raise caving. Both the method and the machine concept, which is an essential part of the mining method, have been developed by LKAB in close collaboration with Montanuniversität Leoben, in Austria. Large-scale testing will begin next year in the Kiruna mine.
Raises are bored and that is the starting point for mining in slices and caving the ore from the bottom to top. This means that mining starts in the raises and is not done horizontally and conventionally by means of so-called drifts. This implies that no people work directly with drilling and blasting, in a conventional sense, within the raises.
The method currently applied in LKAB's underground mines, large-scale sublevel caving, has been very successful. This is an effective method that enables mining of large volumes at a relatively low cost. However, there is some question as to how appropriate this method is for mining at ever greater depth. There are some mines with production at extreme depths, down to as much as 4,000 metres. However, mines in which some form of large-scale caving is applied have not yet reached such depths. And there is a lot of uncertainty as to whether they can maintain viable production volumes in the longer term. Raise caving, as opposed to sublevel caving, is a method that enables mining of the orebody from bottom to top, instead of from top to bottom. In other words, the sequence is reversed, and the technology shift has several advantages, not least in terms of safety.