Ring expansion

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In the front part of the picture ring expansion in a gallery.

In mining, a ring extension is a closed pit extension that consists of assembled steel segments. The ring expansion, also steel ring expansion, is a continuation of the steel arch expansion . Ring expansion is used both in routes and in blind shafts .

history

The first ring expansion was used in German hard coal mining in the second half of the 19th century. At the Graf Beust colliery , elliptical rings were used as an extension for a cross passage . This expansion was later used on other mines . At the Neu-Iserlohn and Glückauf Tiefbau collieries , rings lashed together from four flat arches were used as ring extensions. The arches consisted of double T-beams . Later, flat rings made of pit rails were used on a trial basis at the mines of Hibernia , Mansfeld , Germania and Zollverein . However, this expansion could not prevail because the material was too weak. If thicker profiles were used, they were too heavy and therefore too unwieldy, especially when changing. The very heavy ring expansion was occasionally used in stretches in which there was strong, all-round rock pressure . Iron rings made of U-profiles with a diameter of 2.5 meters were installed at the Neumühl colliery . A cushion made of pit wood with a thickness of 0.5 meters was installed behind the rings as backfilling . This pad was replaced when it was crushed.

construction

The ring expansion has a circular or an elliptical shape. The expansion consists of several segments that are linked together. There are ring expansion with three and ring expansion with four segments. Profile steel rings with four segments are mainly used. A distinction is made between rigid ring expansion and flexible ring expansion. The flexibility of the extension is achieved by sliding tabs or channel profiles. Sliding straps are usually designed as standardized ear clip straps. These brackets are also screwed with four screws outside of the extension segments. By making cuts in the webs of the arch ends, the extension is flexible by 200 to 400 millimeters. In addition to the standardized ear clip tabs, there are also several special designs. The resilience is also achieved by channel profiles that are similar to those of the plain arch construction . At the Prosper colliery , an extension made from so-called Kruppschen was built. These croupes consisted of two rings bent from rails. These rings had an approximately triangular shape with a broad base line. The two symmetrical segments were lashed together at the top and bottom. The individual ring extensions were reinforced with bolts for longitudinal stiffening . In order to protect the steel parts from corrosion , they were reinforced after installation with an inner shell made of shotcrete.

particularities

Ring expansion requires a larger excavation than the route expansion that is open in the bottom . In addition, the miner needs more material for this expansion and the ring expansion is more expensive than the open expansion. Due to the round cross-section of the route that the ring expansion requires, it is hardly possible to work with loading machines. However, ring expansion is more resistant than open expansion. Ring expansion is carried out in rock that is not stable and tends to swell. Ring expansion is also often used to expand the filling points . The closed shape of the ring extension also avoids later countersinking .

Individual evidence

  1. ^ A b c 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 c d e f Carl Hellmut Fritzsche: Textbook of mining science. Second volume, 10th edition, Springer Verlag, Berlin / Göttingen / Heidelberg 1962
  3. ^ A b c Association for Mining Interests in the Upper Mining District Dortmund: 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
  4. ↑ a b c d Ernst-Ulrich Reuther: Textbook of mining science. First volume, 12th edition, VGE Verlag GmbH, Essen 2010, ISBN 978-3-86797-076-1 , pp. 282–286, 339–341.
  5. ↑ 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 .

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