Bad ones
Bad seams are natural interfaces between the seam body . They occur mainly in hard coal seams , but also in the Upper Bavarian pitch coal .
Emergence
Bad ones arise from the tectonic stress on a sedimentary deposit through ore formation processes as a result of the rock pressure acting on the seam body . They run through the seam body in different directions. In practice, a distinction is made between pressure and elongation problems. Poor pressure surfaces have smooth and shiny sliding surfaces, poor stretching surfaces have a fine coating of coal dust or calcite .
Bad ones that continue in the bedrock are called crevices .
Importance in coal production
As the coal still mainly manually with the key pick or the Hammers won was in the "Manual aspirant", the location of the wicked was crucial for individual work designing the Häuer . At the beginning of the shift, the Hauer first had to use the conveyor ( shaking slide or tank conveyor ) to break into the face . Then he worked his way at right angles to the burglary, parallel to the conveyor until the next burglar. Depending on how the bad ones are in relation to the direction of work, the coal is easier or more difficult to remove from the mountain network (the coal “goes”, “coal corridor”). This had a direct effect on the amount of coal mined in one shift.
Work parallel to the bad
If the coal pile is placed parallel to the bad one, the coal dissolves most easily. However, large blocks ( bars ) can peel off and the bad ones may tear open into the hanging wall. The latter is undesirable because there are unnecessary mountains and the roof also has to be removed. With relatively soft coal, there is also an increased amount of fine coal.
Work across the bad
If you put the coal face at right angles to the bad, the coal breaks badly and the tusker "kills himself" without really making any progress.
Work at an angle to the bad
This is the most effective method, both breaking the coal well and avoiding the risk of tearing the hanging wall. The most favorable is an acute angle between the bad and the coal face.
Todays situation
Since manual mining (at least in the industrialized countries) is almost completely a thing of the past and fully mechanized mining, either longwall mining ("machine longwall") with the shearer loader , the coal plow or (in the USA) chamber pillar construction with the continuous miner, is the only mining method, bad ones have today hardly any practical significance. Modern struts are designed so that the machines can be used most effectively, and whether the coal goes well or not does not matter to a machine.
literature
- G. Leithold et al .: Taschenbuch Bergbau . Civil engineering. Ed .: Chamber of Technology, Association of Mining. tape III . German publishing house for basic industry, Leipzig 1962, p. 489 .
- Kurt Hoffmann et al .: Expertise for the hard coal mining . tape 1 . People and Knowledge, Berlin 1952, p. 205 .
- Erich Lewien, Peter Hartmann: Technology of mining . Ed .: University of the German Trade Unions "Fritz Heckert". Fachbuchverlag, Leipzig 1958, p. 210 .
Remarks
- ↑ At the time of manual mining, attempts were made to avoid fine coal and mainly to extract lump coal, as this was easier to extract. In modern, fully mechanized coal mining, this no longer plays a role, since the coal is produced in very fine quantities anyway when mining with the shearer loader and modern power plants do not fire with lump coal but with coal dust. Therefore, the raw coal is ground to a certain grain size for days and a possible or higher proportion of fine coal does not matter.