Site construction

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The Örterbau is a mining method that at flözartigen deposits is applied. This method is always used when individual parts of the hanging wall must not break . The name Örterbau is derived from the tunneling , since with this mining method the excavation areas look like broad local excavations. On-site mining is used in American coal mining for seams with little thickness . But this mining method was also used in the Japanese and British coal mines.

Basics

In the case of deposits that are mined in civil engineering and where the overburden is not sufficiently thick, day breaks can occur if the deposit is completely exploited and not backfilled. For this reason, the deposit is not fully exploited, but individual deposit pillars are left standing. These pillars are known as mountain fortresses or, in the case of steep deposits, as floating. The dimensions of these parts of the deposit (pillars) left unscratched and the distance between the pillars depend on the thickness of the overlying rock and the compressive strength of the mined mineral . In order to improve the supporting effect of the pillars, an additional offset can be introduced into the excavation areas. The mining direction is stroking or cross cutting when building . The direction of prevention runs in the direction of the line axis. Since a large part of the deposit is not mined during this mining process and is therefore sacrificed, there are also large mining losses . In order to reduce this, in deposits with sufficient overburden, the exploited areas are filled with backfill and then the pillars are also dismantled.

The dismantling process

Basic construction

First, one or more seam sections are driven in the seam, depending on the width . The seams are driven as high as the seam thickness . The routes are usually 50 to 100 meters long and at least three meters wide and at most six meters wide. From these seams the sites are driven parallel to each other at right angles. In order to ensure the ventilation of the site, connections ("weather cross-cuts") are made in the pillars at intervals of about 40 meters. Unnecessary voids are filled with an offset. The shape and size of the site is precisely calculated and planned in advance. If the dip is less than five gons , the sites are driven on both sides of the seams. If the incursion is greater, the sites are only opened on one side. The distances between the individual locations and the width of the pillars in between depend heavily on the nature of the overburden. The ratio of the line width to the pillar width is between 6 to 14 and 4.5 to 15.5. As a result of this construction method, there are mining losses of up to 77.5 percent.

Local pillar construction

Principle of the building of local pillars

In order to reduce the mining losses, parts of the pillars are also dismantled. This is done by cutting through the pillars at regular intervals. This method is called local pillar construction. The pillars can have an elongated rectangular, rhombic or square shape. Additional anchors are inserted into the overburden to secure the ridge . So that no too large hanging areas remain open, the locations are connected to one another where possible so that no crossings arise. The pillars are created in such a way that they are offset from one another. With square pillars, a checkerboard-like pattern is created. The pillars and the cavities usually have the same dimensions. But one also speaks of chessboard construction when pillars and cavities do not have the same dimensions. In American mining, this type of construction is known as " room and pillar " mining. With this construction method, the breakdown losses are ideally 50 percent. However, this value is not achieved in practice, as conveyor lines between the pillars must also be created between the excavation areas.

Ortpfeilerbruchbau

If the fortresses between the locations are also dismantled, the mining process is called “ Ortpfeilerbruchbau” . The pillars are then placed in dismantling dismantled. Between the 6-meter-wide villages there are 11-meter-wide pillars, which are then also removed using 6-meter-wide cuts. To protect the local workforce, a 0.5–1.5 meter wide leg of coal is left standing. The roof is often intercepted to secure it with anchors . In another variant, so-called break stamps are set on the break edge, which then remain in place for security. After robbing the rest of the expansion of the corresponding post portion is thrown broken. This collapse is carried out according to plan while maintaining a fault line. This process reduces the degradation losses from around 50–60% to 10–20%.

mechanization

Driving in a thin seam

In the construction of the site, the extraction is largely mechanized. Drilling trucks are used for drilling and loading machines are used to load the debris after the blasting work . In coal mining, mobile cutting machines are used to extract coal . Fully mechanical cutting mining machines, such as the continuous miner , are widely used in American mining . With these machines, shift performances of 400 tons of coal and more are achieved with a relatively small local workforce in the construction of seams with thicknesses of less than one meter. Underground capacities of 10 to 30 tons per man and shift are achieved. Battery-powered trackless vehicles are often used in thin seams with a thickness of up to 1.5 meters. To transport the coal away, shuttling means of conveyance are used, so-called shuttle cars , which are equipped with trackless carriage conveyors. Since the continuous miner can only temporarily store the extracted coal to a limited extent, continuous conveying means are used in some pits to increase productivity. These continuous conveyor systems consist of several eleven-meter-long bridge conveyors that are articulated to one another.

Individual evidence

  1. ↑ a b c d e f g h F. Heise, F. Herbst: Textbook of mining studies with a special focus on hard coal mining. First volume, published by Julius Springer, Berlin 1908
  2. ↑ a b c d e f g h Carl Hellmut Fritzsche: Textbook of mining science. Second volume, 10th edition, Springer Verlag, Berlin / Göttingen / Heidelberg 1962
  3. ^ A b Emil Stöhr, Emil Treptow: Basics of mining science including processing. Spielhagen & Schurich publishing bookstore, Vienna 1892
  4. ^ Förderverein Rammelsberger Bergbaumuseum Goslar eV (Hrsg.): Ore mining in the Rammelsberg. Self-published by the Förderverein, Druck Papierflieger Clausthal-Zellerfeld, Goslar 2009
  5. ^ A b Albert Serlo: Guide to mining science. First volume, fourth revised and up to the most recent edition supplemented, published by Julius Springer, Berlin 1884
  6. ↑ a b Eric Drüppel: Development of a concept for the cutting extraction in rock salt. Dissertation 2010, Rheinisch-Westfälische Technische Hochschule Aachen
  7. ↑ a b c d Wirtschaftsvereinigung Bergbau eV: The mining manual. 5th edition, Verlag Glückauf GmbH, Essen, 1994, ISBN 3-7739-0567-X .
  8. ^ Gustav Köhler: Textbook of mining science. 6th improved edition, published by Wilhelm Engelmann, Leipzig 1903
  9. ↑ Heinz M. Hiersig : Encyclopedia engineering . VDI Verlag, 1997, ISBN 3540621334 .