Surface mining
Open pit mining ( surface mining in Austria ) is an umbrella term from mining. It is a location, be obtained in the near surface mineral resources, without as in underground shafts and / or tunnels are created. Special terms for mining noisy eg " sand pit ", " gravel pit " or " quarry " (with bedrock). Basically, a surface mining is possible without water retention only to the water table. The extraction of building stone in surface mining can be traced to the Stone Age track ( standing stones ). A special form of the mine is being practiced in the U.S. Appalachian Mountaintop Removal mining, in which first hilltops are broken up and removed, and then the raw materials are mined in open pit mining.
Technology
As mining technology all the technical means and measures for the recovery of eg brown coal, gravel, sand and hard rocks are understood.
Lignite, gravel and sand are obtained by dry or wet excavation, hard rock blasted from the deposit or cut out.
The extraction of brown coal, gravel and sand carried by the combination of different mining equipment with downstream transport device. The shape of the recovery is basically divided into continuous and discontinuous.
For the continuous recovery multivessel excavators are used. These include bucket chain excavators and bucket wheel excavator. In Germany, the combination of two units have prevailed. The bucket wheel stacker - combination and the overburden conveyor bridge association (excluding Lusatian mining area ). The International mining equipment also can be found that by milling (Continuous Surface Miner ) and large diameter borehole (Auger Miner ) recover the valuable mineral. The continuous recovery requires following an equally continuous evacuation. Therefore, the transportation from the mining takes place exclusively via conveyor systems that are adapted to the production capacity of mining equipment. A transport by Strossengleis, as he was still partially usual until the end of the 20th century, is now rarely encountered. In Germany the lignite Cottbus- Nord is only operated with this system.
In the batchwise extraction Eingefäßbagger, wheel loaders and excavators are used flat. The Eingefäßbaggern include hydraulic excavators, rope-operated excavators and draglines ( Dragline ). Under flat excavators are understood bulldozer ( Dozer ), Scraper and scrapedozer. In the international mining large-sized devices are used with high capacity. In Germany these are ranked more in the middle to lower size range. As a transport device have been established gravity wagons ( SKW ) and dumpers. Where these vehicles are differentiated by their weight. Until about 60 t total weight is called dumpers, about they are called SKW. The largest currently used SKW have a total weight of 600 t ( Liebherr T282B & CAT 797B ). The transport always ends at a primary crusher. This crushed obtained the material to a usable size for the following processes. The size of the SKW and dumper is adapted to the Chargers hydraulic excavators, rope-operated excavators and wheel loaders.
Environmental impact
With an open pit, especially if there were extensive and many years of operation, first is accompanied by a dramatic landscape change, as well as the soil layers above the raw material to be conveyed, the overburden to be removed. This requires often a massive lowering of the ground water, which has an impact on the surrounding landscapes. The lowering of the water table may occur in adjacent regions to sagging of the ground, the damage to buildings (" surface damage " ) can cause. The pumped groundwater is usually introduced into surrounding rivers or seeps to the conservation of wetlands in open pit nearby. A significant part of the upper groundwater is used in surface mining to pollution control purposes and as a fire-fighting and domestic water.
During the ongoing mining operation of the accumulating overburden is usually used on the tilting side of the resulting hole to backfill. Then usually there is a so-called restoration of the landscape: it is agricultural land, forest land and / or recreation areas created. Because of space requirements and the impact on landscape and groundwater was and adjusting of surface mines is often controversial. For the operation of an open pit sometimes entire villages to be relocated - see also: List abgebaggerter villages.
From reclaimed surface mines often arise " biotopes second hand ", new lakes landscapes and recreational areas. Examples are the Geiseltalsee at Merseburg, the Lake Senftenberg, Leipzig New Lakeland, the Blausteinsee in Eschweiler and Sophie height at Jülich and the Upper Palatinate Lakeland.
The largest open pit in the world is located in the Chilean Chuquicamata.