Mine support
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Door frame extension
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With mine roof or expansion is known in mining the Secure and maintain open spaces underground. The term refers collectively to all processes to support or solidification of the rock (also Mountain lead) set up to be backed cavity ( tunnel , tunnel , cavern surrounds).
Basics
Only in a few areas of the mine can one get along without any expansion. The mine workings are often heavily burdened by convergence as a result of mining effects and must be secured by appropriate measures. Basically, the expansion is introduced in such a way that the required clearance profile of the pit is maintained. Accordingly, the need tunneling a larger excavation profile will be excavated. This is necessary because there are secondary stresses around the mining cavity, which mechanically stress the rock or the rock. Due to the rock pressure , the rock tries to backfill the created cavity. In mining, a distinction is made between shaft expansion , route expansion and longwall construction .
Tasks of the expansion
The job of the extension is to protect the miners from falling rocks. In addition, the expansion should be given a minimum cross-section in the expanded pits. The cross-section must be so large that weather management , driving and conveyance are not hindered. In addition, the expansion should prevent the penetration of pit water into the mine workings as well as the complete collapse of the mine workings. Furthermore, if possible, the rock pressure should not only be completely absorbed by the expansion, but should also be fed back into the mountains.
Usable materials
As finishing materials are wood , stones , metal and concrete used.
Wood
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The pit lining out of wood is called pit rooming. All types of wood are suitable for pits; some types of wood have particularly proven themselves. Hard or resinous woods are best suited. The wood must have a certain thickness and strength. Woods that are well suited for the pit room are hard hardwoods such as oak, beech and alder or conifers such as fir and spruce. Pit rooms made of oak are particularly resistant to moisture, high temperatures and so-called sluggish weather. To make the pit room resistant to moisture and rot, the woods are impregnated with salt solutions for days . The salt solution penetrates the wood and displaces the wood sap. Wood as a construction material has the advantages that it is inexpensive to obtain and easy to work with, and wood is lighter than other construction materials. The disadvantage of wood is that it can usually not be used again after it has been used. Wood cannot be used everywhere either; it is flammable, not weatherproof and only withstands a low pressure load. The storage costs and the transport costs are relatively high.
Stones
The excavation of the pit using bricked stones is called pit walling. In the past, only the wheel rooms of the artificial bikes were provided with a pit wall. For this purpose, the rocks that were extracted during the mining process were appropriately processed and used. The pit walls were also built from rubble stones or bricks extracted from the surface. A distinction is made between the dry and the wet walling of the pit wall. With dry masonry, masonry is carried out without binding agents; with wet masonry, binding agents such as lime and mortar are used . Quarry stones are used for dry masonry, while natural stones, bricks, smelting stones, sand-lime bricks or molded concrete blocks are used for wet masonry.
metal
The expansion of metal was increasingly used in mining when iron was cheaper (cheaper) to acquire. Iron was initially used in mine workings, where pit wood rotated quickly and easily. In the 19th century, cast iron and wrought iron were used as finishing material. Stamps were made from cast iron and used. In the first half of the 20th century, stamps made of light metal were also used. Today only steel is used for the metal pit lining . For this purpose, specially shaped profile parts or segments made of steel are used (in the flexible version: plain arch construction ). The steels that can be used must be standardized. The advantages of the construction with steel are the high compressive strength of the steel and its recyclability. Steel construction is non-flammable and can be introduced partly mechanically. Both the high costs and the possible total failure of the extension are disadvantageous.
concrete
When lining with concrete, a distinction is made between lining with precast concrete parts, so-called segments , and shotcrete lining (→ New Austrian Tunneling Method # Secure ). The shotcrete lining is applied to the roof or the joints using the wet or dry spray method and hardens there. This strengthens the mountain by preventing weathering as much as possible. The shotcrete shell also has a supporting effect. This type of construction is combined with anchor construction on site, with the anchored braids serving as reinforcement for the concrete.
Procedure
Support extension
A further distinction is made between rigid, articulated, flexible and articulated-flexible structures.
- The rigid expansion is mainly used in areas where no cross-section changes or narrowing of the mine are to take place or where only little rock pressure is expected. This usually affects main routes, filling locations and caverns such as workshops or the like. Wooden construction elements (door frame), arched steel construction elements (arch construction ) or masonry are used.
- The articulated extension reacts to rock movements by evading and deforming the cross-section without reducing the clearance profile.
- The flexible extension (e.g. sliding arch extension ) evades loads from the rock by sliding the extension elements into one another and thus avoids high stresses on the extension material. The disadvantage is the narrowing of the cross-section, which can lead to the loss of navigability on the route.
Anchor support
The anchor construction principle is based on the connection of rock layers, so that around the cavity to be secured a rock package is created that has greater resistance than the individual layers. In this respect, the anchor reinforcement represents a strengthening of the rock. Different types of anchors are used, depending on the place of use, load and purpose. These can be combined with warping mats or other meshes. Anchor support has the advantage that it can be produced quickly and installed fully mechanically. It is not flammable and there are only low transport costs. However, the work involved in bringing it in is high and it is not recyclable. In addition, the attachment of materials and lifting devices is only possible to a limited extent and the anchor extension cannot be used in all mountain conditions.
Planning and selection
When selecting the extension, the planning engineer must consider several points. In particular, the expected rock pressure must be taken into account. The rock movements associated with the rock pressure also have an influence on the selection of the extension. The area to be supported and the required service life of the extension are further factors that the extension engineer must consider. In the planning, the time span that elapses between the excavation of the mine and the introduction of the support must also be taken into account. Whether a rigid or flexible extension is installed depends on the local conditions. In particular, the type of hanging wall, the collapse and, in the dismantling area, the dismantling method have an influence on the selection of the extension. All of these factors decide which finishing material, which finishing type and which finishing density are used.
Individual evidence
- ↑ a b c d e f Walter Bischoff , Heinz Bramann, Westfälische Berggewerkschaftskasse Bochum: The small mining dictionary. 7th edition, Verlag Glückauf GmbH, Essen, 1988, ISBN 3-7739-0501-7 .
- ^ A b Ernst-Ulrich Reuther: Introduction to mining. 1st edition, Verlag Glückauf GmbH, Essen, 1982, ISBN 3-7739-0390-1 .
- ↑ a b c d e f g h Heinz M. Hiersig (Ed.): VDI-Lexikon Maschinenbau. VDI-Verlag GmbH, Düsseldorf 1995, ISBN 978-3-540-62133-1 .
- ↑ Otto Proempeler, Hermann Hobrecker, Günther Epping: pocket calendar for mine officials of the coal industry in 1956. Karl Marklein-Verlag GmbH, Dusseldorf 1956th
- ↑ a b c d e f Carl Hellmut Fritzsche: Textbook of mining science. Second volume, 10th edition, Springer Verlag, Berlin / Göttingen / Heidelberg 1962.
- ↑ a b c d e Albert Serlo: Guide to mining science. First volume, published by Julius Springer, Berlin 1884.
- ^ A b Emil Stens: About yielding pit support. In: Glückauf, Berg- und Hüttenmännische magazine. Association for Mining Interests in the Upper Mining District Dortmund (Ed.), No. 17, Volume 47, April 29, 1911, pp. 649–660.
- ↑ a b Explanatory dictionary of the technical terms and foreign words that occur in the mining industry, in metallurgy and in salt works, and technical art expressions that occur in salt works. Falkenberg'schen Buchhandlung publishing house, Burgsteinfurt 1869.
- ↑ a b c Types of expansion on headframes in Bergbau.de (accessed on November 4, 2011).
- ↑ Pit expansion at Zeno.org (accessed November 4, 2011).
- ↑ K. Eisenmenger: Development and status of the expansion of main lines in Ruhr mining. In: Glückauf, Berg- und Hüttenmännische magazine. Association for Mining Interests in the Dortmund Oberbergamtsgebiet (Ed.), 71st year, January 5, 1935, pp. 2-10.
- ↑ Horst Roschlau, Wolfram Heinze, SDAG Wismut (Hrsg.): Knowledge storage mining technology. 1st edition. Deutscher Verlag für Grundstofftindustrie, Leipzig 1974, pp. 78–96.
- ↑ Mountain anchors, especially for mining. Patent No. DE3532069A1 March 26, 1987 (accessed November 3, 2011).
- ^ Ernst-Ulrich Reuther: Textbook of mining science. First volume, 12th edition, VGE Verlag GmbH, Essen 2010, ISBN 978-3-86797-076-1 .
