Track dam

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A roadside embankment is an underground structure that serves to secure the edge of the line in the mining lines against the old man during longwall mining . Roadside embankments are made from different building materials, depending on whether they have to be rigid or flexible. There are certain calculation methods for determining the supporting force of roadside embankments.

Manufacturing

There are two basic methods for creating roadside embankments, creation using cladding walls and creation using large, prefabricated fabric sacks, so-called bullflex hoses.

One of the first methods of creating roadside embankments was to create them with solid casing walls . Here, the dam was created by blowing building material between two cladding walls, the cladding wall on the track side had a curvature that was adapted to the expansion curve. With this method, the dam was built very early on, close behind the conveyor. The disadvantage here was the relatively large hydraulic expansion effort, including the necessary control technology. In addition, with this method it is relatively difficult to maintain the intended width of the roadside embankment in the long term. However, an early-bearing, stable roadside dam cannot be guaranteed. Another disadvantage is that the die extension that carries the formwork wall is very complex, since it requires a separate pulling and tensioning unit.

In another method, the roadside embankment is created using a dam with adjustable shuttering walls. The formwork panels are arranged on a special construction so that they are aligned vertically. The dam construction trestle is equipped with narrow support frames which serve to support the cladding walls. The entire dam trestle can be effectively aligned in the longitudinal axis of the route and in the strut as required. In addition, the trestle can be placed at an angle in the area of ​​the roof or the base or it can be straightened. The shuttering walls are connected to a rear device and serve to surround the dam construction material. With a width of around 0.7 times the seam thickness, around 1–2 m 3 of building material are required per meter of dam . The dam is widened to prevent the edge protection from slipping off in the case of solid rock. Pneumatic backfilling achieves adequate dam quality with acceptable dust generation.

Another method is to create the roadside embankments with sack-like containers, so-called Bullflex pillars. However, creating the roadside embankments using Bullflex pillars is more expensive in terms of manufacturing effort. A special type of pillars are so-called stacking pot pillars. A stacking pot pillar consists of several nested vessels that are open at the top and filled with support material at the place of use. They are filled in with support material and then placed on top of one another. Using aids such as B. active support sleepers, stacking pot pillars are braced between hanging and lying. High support forces are achieved relatively quickly with pillars, as they are built up behind the longwall at an early stage. This makes convergences less of a disadvantage.

used material

The crates required for this are lined with weather cloth , geotextiles or jute so that the dam construction material cannot run away in a liquid or doughy state from conventionally constructed roadside dams . In the case of building material mixtures made from natural anhydrite and electrostatic precipitator ash, the building material mixture solidifies after a setting time of around 45 minutes. To accelerate the setting process, soda water glass is added to the liquid building material. However, the load-bearing capacity of the dam is not precisely defined and the necessary supporting forces are only available after the building material has completely set. The maximum compressive strength of the building material is only reached after several days. Special injection resins are used to seal leaky roadside embankments.

Individual evidence

  1. ^ Walter Bischoff, Heinz Bramann, Westfälische Berggewerkschaftskasse Bochum: The small mining dictionary. 7th edition, Verlag Glückauf GmbH, Essen 1988, ISBN 3-7739-0501-7 .
  2. ↑ a b Christian Sauer: Development of an alternative strut shield to increase the degree of automation at the face crossings of German hard coal mines under mechanical engineering and occupational safety aspects. Dissertation at Clausthal University of Technology, Clausthal 2009.
  3. ↑ a b Patent DE4402358A1 August 3rd, 1995 stacking pot pillars (last accessed on May 18, 2015).
  4. ↑ Patent DE19915939B4 02/28/2008 Dam construction trestle with adjustable cladding walls (last accessed on May 18, 2015).
  5. ^ Ernst-Ulrich Reuther: Textbook of mining science. First volume, 12th edition, VGE Verlag GmbH, Essen 2010, ISBN 978-3-86797-076-1 , pp. 569-571, 575, 576.
  6. ↑ Resins in Mining ( Memento from February 15, 2010 in the Internet Archive ) (PDF; 1.1 MB).