Rigid arch extension

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Rigid arch extension

The rigid arch support is a rigid teilelliptischer roadway support , which in mining underground is used. The rigid arch support is used in long-lasting pit structures in alignment , in main routes, filling locations and workshops. The rigid arch construction usually consists of several individual steel segments with a web profile . Single-leg, symmetrical solid wall profiles (HEA, HEB, INP) are used as steel profiles. Rigid arch construction must comply with the DIN 21531-1 or DIN 21531-2 standards.

history

As early as 1869, the Hannibal colliery was tested for the first time with rigid arch support in a section . The extension consisted of three - part cast iron arches with a T-profile. However, this expansion did not prove itself as the material was unsuitable for use. Subsequently, pit rails were used instead of the cast iron T-profiles . The extension consisted of two rails, which were curved in a semicircle in the upper area. The two half-arches were lashed together in the upper area to form a straight arch. The lower ends of the rails were fitted with cast iron feet. The first iron lining was unsuitable for strong rock pressure . In a mine in Upper Silesia, strong railway tracks were already bent after a short period of use. In the Harz mining industry, where the rigid arch extension was used in field stretches over which mining had already taken place, the extension of the line was totally bent despite the short construction distance. Towards the end of the 19th century, arch extensions were hardly ever used in the Ruhr district. From the middle of the century onwards, arches were increasingly used again in the main routes.

construction

Rigid arch extension in the sole area open

There are two different types of rigid arch extensions: These are the rigid arch extensions, which is open in the sole area , and the rigid arch extensions, which are closed in the sole area. The most common is the steel arch construction, which is open in the sole area. A distinction is made between different arch forms, the round arch, the horseshoe arch and the portal arch. In the case of a round arch, the lower extension parts are shaped so that they run down vertically. With the horseshoe arch, the lower parts of the extension are slightly curved inwards. In the case of the portal arch, the lower extension parts are directed outwards at an angle. The expansion consists of individual segments that butt together. Bar profiles are mostly used as profiles, either GI or wide flange profiles. The individual segments are connected to one another by straps. There are different types of tabs, of which the clip tabs have proven to be the best. These brackets completely clasp the profile of the extension segment and can transfer higher bending moments than the individual extension segments. Flat iron plates and U-plates have not been able to prevail due to their lack of strength. The arch extension closed at the bottom has a similar structure to the arch extension open at the bottom. This type of extension was used in the area of ​​the filling points when the lying area was swelling. There were arches with straight and curved sole bars. The longitudinal stiffening between the individual extension arches is carried out using appropriate bolts .

properties

With a rigid arch construction, the height increases according to the width of the sole, but it is always 20 to 30 percent smaller than the width of the sole. Due to its arch shape, the rigid arch extension is superior to the door frame extension in terms of load-bearing capacity. If the maximum load-bearing capacity of the rigid arch support is exceeded, the individual support segments are deformed. The expansion kinks to the side or front. The deformation of the segments is usually so strong that the segments can no longer be straightened . In order to better protect the expansion segments from deformation, the strength of the clamp bracket is weakened. The standard therefore stipulates a lower quality of steel for the clamp straps . In order to achieve a slight flexibility in web profiles, so-called sliding tabs are used to connect the segments with these profiles. A certain resilience is also achieved by using drop supports .

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. ↑ Horst Roschlau, Wolfram Heinze, SDAG Wismut (Hrsg.): Knowledge storage mining technology. 1st edition. German publishing house for basic industry, Leipzig 1974, p. 80.
  3. ↑ a b c Ernst-Ulrich Reuther: Introduction to mining. 1st edition, Verlag Glückauf GmbH, Essen, 1982, ISBN 3-7739-0390-1
  4. ↑ a b c Alexander H. Schneider: Security against collapse in underground mining. ETH dissertation No. 14556, Institute for Geotechnics, vdf Hochschulverlag AG at ETH Zurich, Zurich 2002, ISBN 3-7281-2872-4
  5. ↑ Directory of Mining Standards. Status 03.2015 Online ( Memento from March 7, 2010 in the Internet Archive ) (accessed on April 20, 2015).
  6. ^ A b Association for Mining Interests in the Upper Mining District Dortmund (ed.): The development of the Lower Rhine-Westphalian hard coal mining in the second half of the 19th century. Julius Springer's publishing bookstore, Berlin 1902.
  7. ↑ a b c Gustav Köhler: Textbook of mining science. 2nd edition, published by Wilhelm Engelmann, Leipzig 1887.
  8. ^ Joachim Huske: The coal mining in the Ruhr area from its beginnings to the year 2000. 2nd edition, Regio-Verlag Peter Voß, Werne, 2001, ISBN 3-929158-12-4 .
  9. ^ A b c d e Carl Hellmut Fritzsche: Textbook of mining science. Second volume, 10th edition, Springer Verlag, Berlin / Göttingen / Heidelberg 1962