The rock layers covering the useful mineral are referred to as overburden in open-cast mining .
Opencast lignite mines
When a lignite mine is re-opened, the topsoil is first removed and stored separately for later recultivation. Then the overburden layers lying on the coal seam , which usually consist of quaternary and tertiary layers in lignite mining , are cleared and stored on dump . When re-opening the dump is inevitably outside the open pit and is therefore referred to as the outer dump . If the mining of the lignite has progressed far enough later, the overburden that then arises is dumped into the charred space, which is referred to as the inner dump . In the course of recultivation, the outer dump is mostly removed today and also collapsed in the charred open-cast mine.
Depending on the thickness of the overburden, the overburden is excavated in one or more steps. For this purpose, the preliminary cut is first made in a deep cut from the surface using a bucket chain excavator ; a further excavator set up deeper for him in high cut , if necessary a third excavator located on the same subgrade, again in deep cut.
The overburden must be conveyed around the open pit to the dump side. This is done by conveyor belt or train operation or directly across the opencast mine with a conveyor bridge. The excavators convey the overburden either onto the conveyor belt or the trains. In the case of conveyor bridge operation , high and deep cut excavators are coupled to this.
On the dump side, the overburden is tipped by the spreader .
Ore and deep open pit mines
Ores and raw materials other than lignite are also extracted in open-cast mining. Due to the mostly non-seam-like formation of the deposit bodies, a different technique is used here. Overburden and useful minerals are extracted by shovel or dragline excavators; Because of the generally higher rock strength, blasting usually has to be carried out. The excavators load the overburden into large dump trucks with a transport capacity of up to 360 tons / vehicle and then move them to the outside dump . An inside dump is usually not possible, as mining in these opencast mines is concentrated in a confined space and there is not enough space available.
- Ernst-Ulrich Reuther: Introduction to mining. 1st edition, Verlag Glückauf GmbH, Essen 1982, ISBN 3-7739-0390-1
- Erich Lewien, Peter Hartmann: Technology of mining . Ed .: University of the German Trade Unions "Fritz Heckert". Fachbuchverlag, Leipzig 1958, p. 93-104 .
- Б. В. Бокий: mining science . Technology, Berlin 1955, p. 451–506 (Russian: Горное дело . Translated by R. Staepken).