Longwall mining

Longwall scheme; Shearer loader and self-propelled shield support

The longwall is a mountain architectural degradation processes in underground mining , which in flözartigen deposits will be applied. Other names for the longwall are Streichendbau or Streckbau . However, these terms are hardly used today. In English, the process is known as long wall mining . Of the mining methods used in underground mining, longwall mining is the safest and most productive method. In German hard coal mining, longwall mining is used exclusively for hard coal mining.

history

Longwall mining comes from the Mansfeld copper slate mining and was used as a mining method from the 19th century, mainly on coal mines. Initially, the process was limited to flat to slightly inclined seams with a maximum thickness of 2 meters. The length of the face was limited to 8–12 meters due to the difficult transport. This forced the respective construction site to be divided up by a corresponding number of seams. In addition, so-called safety pillars had to remain in place. The coal was extracted with a wedge pick , later with a hammer . The extracted mineral resources were transported away by wagon transport with Hunten . With the advent of mechanization, especially with the removal of coal, the face lengths could be increased significantly. Face lengths of 100 to 300 meters are becoming more and more popular.

Basics

Longwall mining is usually a rectangular Flözabschnitt is progressively Spanking . Copper shale seams and hard coal seams are mined by longwall mining . The mining face on which the extraction takes place is called the mining front. It is characteristic here that several impacts are driven forward at the same time. Depending on the direction of mining, a distinction is made between striking, floating or falling longwall mining. The mining area in which the longwall mining takes place is called the longwall . The longwall is accompanied on each side by a mining section . In longwall mining, mining is carried out by guiding the longwall to the field between the two mining stretches, starting from a cut. A distinction is made between the front end and the demolition . The mined area behind the longwall that has already been discarded is known as the Old Man . This area is filled with offset . There are different offset methods for this. The displacement method that is most commonly used is fracture displacement . Longwall mining is suitable as a mining method in seams with a smaller thickness and with little falls . Manageable in longwall are widths of up to four meters and dip of about 40 Gon . For larger seams, special measures such as B. It is necessary to divide the seam into two banks. Other mining methods are used for incursions greater than 40 gons. The mining of steep seams is particularly problematic. Here the miner has to take special care that the offset does not slip into the routes. This can and must be prevented by carefully compensating for the offset. Mining in steep seams is only used very rarely worldwide. Since larger slopes are exposed at the same time in longwall construction, the adjacent rock must have sufficient strength in longwall construction . This is necessary so that the mountains do not collapse prematurely. If the hanging wall behind the longwall is deliberately thrown to pieces, this process is known as longwall construction.

Procedure and direction

The longwall is part of the long-front type of construction. Mark here is that the extraction of the mineral takes place on a long front. Depending on whether the working face advances in the direction of strike, the direction of fall or diagonally between these two directions of the seam , a distinction is made between striking, floating and diagonal longwall mining.

Striking longwall

Scheme of longwall mining with offset
(green: strike stretches, gray: seam, orange: old man, red: mining face)

Strike longwall mining is a technique in which the direction of mining is the direction of the strike line of the deposit . A characteristic of this process is that the excavation front is worked on both its entire and half of its length on each extraction layer. The collapse does not play a major role in longwall mining. The method is suitable for flat, moderately inclined and steep storage . The position of the bad in connection with the angle of fall has a greater influence on the execution of the procedure . The method is used when the collapse of the seam is between about 20 and 40 gons or when the bad ones are mostly floating in the coal. It is the most widely used method, especially for seams with a thickness of three to four meters. However, the method is also suitable for seams with a smaller thickness, with heavy landslides or after-fall.

In preparation for mining, the seam is prepared by two parallel seam sections , also called strike sections . The lower foot section serves as a conveying section, the upper head section as a weather section . These two stretches of seam are connected by hacking . This hacking forms the longwall during dismantling. In the longwall, the roof is supported with punches and caps . The weather is directed through the walled area with the help of weather doors . If the direction of propulsion runs in the same direction as the direction of mining in the case of striking longwall mining, one speaks of striking longwall with striking forwarding . Coating longwall mining is the most frequently used longwall mining method in the Ruhr area.

Floating longwall

In this form of longwall mining, the entire mining front is propelled in a floating manner. The prerequisite for the floating longwall mining are coal seams that have no methane outgassing and thus do not release any heavy weather . The collapse of the seam may not exceed 33 gon . In the case of larger invasions, there is a greater risk of coal falling with the floating longwall. In addition, it is more difficult to relocate the face conveyor with larger invasions. In the case of manual conveying , the dip may not exceed 5.5 gon. Good ventilation is particularly important for floating longwall structures. To achieve a good ventilation, one is first weather punch to the upper sole created. For this purpose, an overhaul is created as a connection. The floating mining operations are then connected to this overhaul. The weather connection is made via weather roses . The weather can, where necessary, be derived by means of a weather bridge .

With the floating longwall, more struts can be set up and operated with the same field size. In order to operate several mining operations, the route used for driving and conveying is kept open and not moved with mountains. As soon as the first longwall has moved into the field, the second operation is started. The other struts then follow the same scheme. The method even enables the mining of seams that are not worth building with the longwall mining . In every mining operation, two excavations form the wall boundaries, the mining is chosen with a view to the easier extraction of the coal perpendicular to the direction of strike, against the falling. If the mountain offset is used in this process, the mountains often have to be delivered from other operating points or from above ground. In the case of steep storage, the foreign mountains can be collapsed for all mining operations together over the weather.

Diagonal longwall

With diagonal longwall mining, the mining direction is just as diagonal as the direction of the following conveyor lines. Diagonal mining has the advantage that a mining field of considerable length with a large number of points of attack can be excavated. In this way, a quantity of funding is achieved that was not so easily possible when the mining operations were being carried out and that only improved through optimization of the delivery techniques. To ventilate struts that are operated in seams with a high methane content, a weather rose has to be installed to return the flow of air. For the diagonal longwall, the collapse must not be greater than 17 gon and it can only be used where there is no risk of firedamp. Since these conditions can hardly be met, the diagonal longwall is no longer used today.

Excavation face

Depending on the mutual position of the mining joints to one another, the miner speaks of longwall mining with a broad view and longwall mining with remote joints. The longwall with a broad view is the actual longwall. The dismantling front is dismantled in an uninterrupted straight line. This avoids recessed corners. This has great advantages in terms of ventilation . The straight working face, in particular in mines with firedamp hazards which prevent the accumulation of fire damp. Longwall mining with a broad view is used in particular in longwall struts in which cutting machines are used for mining . In the case of fully mechanical extraction in particular, it is essential that the mining front is as straight as possible. The uniform advancement of the dismantling front also prevents the hanging wall from breaking through, especially in the area of painted edges. This also reduces the risk of falling rocks and coal. In addition, the rock pressure can also be distributed more evenly over the offset . Furthermore, the operation processes in the face can be better monitored by keeping the mining front as straight as possible. Longwall mining with a broad view is suitable for deposits with little dip.

With longwall construction with offset joints, the mining front does not form a straight line, but, similar to the roof construction , an inverted stair-like shape. This form of longwall construction is also very similar to shock construction and is therefore often referred to as such. This form of longwall mining is particularly applicable to steep seams. When using this procedure, the lower thrusts are allowed to proceed. This is necessary so that one does not have to drive over the hollow space between the mountain offset and the coal face of the lower strut in the mining sections. The rock pressure has an unfavorable effect on longwall mining with offset impacts in the area of the protruding corners.

mechanization

Mechanization is a critical component of longwall mining performance. The first partial mechanization was achieved with the introduction of the vibrating slide at the beginning of the 20th century. Further improvements were the use of cutting machines , the scraper chain conveyor and the fully mechanized expansion .

Extraction

Coal planer on armored conveyor, expansion using rubbing punches and steel joint caps

The mining of longwall is now almost entirely mechanized. Manual extraction using a hammer is now only limited to small areas and has largely become meaningless. In mechanical extraction, a distinction is made between ramming extraction, peeling extraction and cutting extraction. Since the piling equipment required for ramming was not widely used, this method could not prevail in longwall mining. Various cutting machines (rotary cutter loader, frame cutter loader) are used for cutting mining. These run on the conveyor (usually an armored conveyor), use their chisels to cut the coal from the composite and convey it onto the conveyor. The cutting extraction has advantages over the peeling extraction with moderately inclined seams from a depth of 40 gon. The peeling extraction takes place with a coal plow drawn on the offset side . These mining machines can be used in struts with a dip of up to 60 gon. Due to the universal applicability and the simple structure of the coal plow, peeling extraction is the most widespread of all processes. During extraction, the plow is pressed against the coal face with the help of return cylinders. This allows the plow's chisels to penetrate the coal seam and practically tear open the coal face. The dissolved coal is simultaneously loaded onto the side of the face conveyor.

Copper shale mining

Longwall with a broad view

Longwall mining with a broad view was used in the Mansfeld copper slate mining until around 1908, on the upper levels. The direction of mining was carried out by painting, the direction of mining was also by painting. The longwall was either straight or diagonal. The removed cavity was moved by hand with the "roof mountains". In the offset, alleys were painted as conveyor lines ("conveyor run") and with increasing face length also auxiliary brake mountains were left out.

Arched struts

With the mining advancing into ever greater depths, the longwall mining caused increasing problems with the control of the hanging wall due to the higher rock pressure. For this reason, arched strut mining was developed, which allowed the rock pressure to be exploited to the advantage of mining the copper shale with a hammer in a floating direction of mining and arching. An arched strut dismantling consists of a different number of individual arches. Starting from the bottom, the longwall is hewn upwards ("floating"). An approximately circular arc is expanded into an ellipse until it finally grows together with the neighboring arcs. Conveyor trips and the brake mountain are left out in the offset. If a flat distance of about 80 m from the bottom section is reached, a mining section is cut out parallel to this, which connects the conveying runs in the sweeping direction. When 80 m have been hit again, the next mining section is laid. Conveyor runs, mining sections and braking mountains are torn down in the hanging wall in order to reach at least 1.1 m section height, while the struts are only 80 cm high. The width of a buttress is about 25 m.

Straight bracing with scraper

In Mansfeld copper slate mining, in addition to traditional arched struts, the so-called scraper struts developed in the 1970s , a variant of peeling extraction with floating mining direction and brushing, were used in the Mansfeld copper slate mining industry. Due to the geological peculiarities of the copper shale seam (little to no collapse, low thickness of only around 40 cm, greater hardness of copper slate than coal), the rock pressure is used to prepare the seam for extraction. First, a dismantling area consisting of several struts is prepared by head and foot sections, which are connected by boundary flat . In parallel to these excavation routes, the excavation area is divided into 15 to 20 m wide individual struts. In the next step, horizontal relief holes with a diameter of 160 mm at a distance of around 40 cm are made in the struts. This creates relief cavities so that the rock pressure can loosen the seam. Only then does the actual extraction take place with the scraper. In contrast to the coal plow, the scraper is both an extraction and a conveying tool. The extracted copper ore is conveyed to the transfer point in the footpath by further scrapers in the mining sections. The removed area is expanded with support bodies.

Individual evidence

↑ ^a ^b ^c ^d ^e ^f ^g ^h ⁱ ^j ^k ^l ^m ⁿ Carl Hellmut Fritzsche: Textbook of mining science. Second volume, 10th edition, Springer Verlag, Berlin / Göttingen / Heidelberg 1962
↑ Wolfgang Reichel, Manfred Schauer: The Döhlener basin near Dresden, geology and mining. Saxon State Office for Environment and Geology (LfUG), Saxoprint GmbH Dresden, Dresden 1983, ISBN 3-9811421-0-1 .
↑ Frank Otto: Different ideas of "Long Wall Mining" . In Ring Deutscher Bergingenieure eV (Ed.) Bergbau, Volume 8, 62nd year, Makossa Druck und Medien GmbH, Gelsenkirchen August 2011, ISSN 0342-5681 , p. 365
↑ Ulrich Lange: Shearer longwall mining simulation. Approved dissertation, Rheinisch-Westfälische Technische Hochschule Aachen, Aachen 2009, pp. 19–30
↑ ^a ^b ^c ^d ^e ^f Heinz Kundel: coal production. 6th edition, Verlag Glückauf GmbH, Essen 1983, ISBN 3-7739-0389-8 .
↑ ^a ^b ^c ^d Georg Spackeler, Waldemar May: Bergbaukunde . 8th training letter for dismantling II. Ed .: Main Department of Distance Learning at Bergakademie Freiberg. 2nd Edition. Deutscher Verlag der Wissenschaften, Berlin 1957, p. 8 / 13-8 / 20 .
^ Emil Stöhr, Emil Treptow : Basics of mining science including processing. Spielhagen & Schurich publishing bookstore, Vienna 1892
↑ ^a ^b ^c ^d ^e ^f ^g ^h ⁱ ^j ^k Ernst-Ulrich Reuther: Introduction to mining. 1st edition, Verlag Glückauf GmbH Essen, 1982, ISBN 3-7739-0390-1 .
^ ^A ^b Albert Serlo: Guide to mining science. First volume, fourth revised and up to the most recent edition supplemented, published by Julius Springer, Berlin 1884
^ ^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
↑ ^a ^b ^c ^d ^e ^f ^g ^h ⁱ ^j F. Freise: Alignment, installation and mining of hard coal deposits. Publishing house by Craz & Gerlach, Freiberg in Sachsen 1908
↑ ^a ^b ^c ^d ^e Emil Stöhr: Catechism of Mining Studies. Lehmann & Wentzel bookstore for technology and art, Vienna 1875
↑ ^a ^b ^c ^d ^e ^f ^g ^h ⁱ ^j F. Heise, F. Herbst: Textbook of mining studies with special consideration of hard coal mining. First volume, published by Julius Springer, Berlin 1908
↑ Christian Mues: Development of an extraction and expansion system for underground mining. Approved dissertation, Clausthal University of Technology, Clausthal 2008, pp. 13-14
↑ ^a ^b ^c ^d ^e ^f G. Köhler: Textbook of mining science. 2nd edition, published by Wilhelm Engelmann, Leipzig 1887
^ 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
↑ Dr.-Ing. Erich Lewien, Peter Hartmann: Technology of mining . Ed .: University of the German Trade Unions "Fritz Heckert". Fachbuchverlag, Leipzig 1958, p. 88 .
↑ Collective of authors: Basic Geological Knowledge . Ed .: Horst Roschlau, Hans-Joachim Haberkorn. 2nd Edition. German publishing house for basic industry, Leipzig 1977, p. 146 .
↑ Horst Roschlau, Wolfram Heinze: Knowledge storage mining technology . Ed .: SDAG Wismut. 1st edition. German publishing house for basic industry, Leipzig 1974, p. 233 ff .
↑ Georg Spackeler, Waldemar May: Mining Studies . 8. Dismantling lesson III. Ed .: Main Department of Distance Learning at Bergakademie Freiberg. 2nd Edition. Deutscher Verlag der Wissenschaften, Berlin 1957, p. 8 / 13-8 / 20 .

Remarks

↑ A weather overburden is a mine that is built in the seam from bottom to top and is used for ventilation . (Source: Tilo Cramm, Joachim Huske: Bergman language in the Ruhr area. )

[Quelle_1-1] ↑ ^a ^b ^c ^d ^e ^f ^g ^h ⁱ ^j ^k ^l ^m ⁿ Carl Hellmut Fritzsche: Textbook of mining science. Second volume, 10th edition, Springer Verlag, Berlin / Göttingen / Heidelberg 1962

[Quelle_9-2] Wolfgang Reichel, Manfred Schauer: The Döhlener basin near Dresden, geology and mining. Saxon State Office for Environment and Geology (LfUG), Saxoprint GmbH Dresden, Dresden 1983, ISBN 3-9811421-0-1 .

[Quelle_10-3] Frank Otto: Different ideas of "Long Wall Mining" . In Ring Deutscher Bergingenieure eV (Ed.) Bergbau, Volume 8, 62nd year, Makossa Druck und Medien GmbH, Gelsenkirchen August 2011, ISSN 0342-5681 , p. 365

[Quelle_14-4] Ulrich Lange: Shearer longwall mining simulation. Approved dissertation, Rheinisch-Westfälische Technische Hochschule Aachen, Aachen 2009, pp. 19–30

[Quelle_8-5] ↑ ^a ^b ^c ^d ^e ^f Heinz Kundel: coal production. 6th edition, Verlag Glückauf GmbH, Essen 1983, ISBN 3-7739-0389-8 .

[Abbau2-6] Georg Spackeler, Waldemar May: Bergbaukunde . 8th training letter for dismantling II. Ed .: Main Department of Distance Learning at Bergakademie Freiberg. 2nd Edition. Deutscher Verlag der Wissenschaften, Berlin 1957, p. 8 / 13-8 / 20 .

[Quelle_2-7] Emil Stöhr, Emil Treptow : Basics of mining science including processing. Spielhagen & Schurich publishing bookstore, Vienna 1892

[Quelle_7-8] ↑ ^a ^b ^c ^d ^e ^f ^g ^h ⁱ ^j ^k Ernst-Ulrich Reuther: Introduction to mining. 1st edition, Verlag Glückauf GmbH Essen, 1982, ISBN 3-7739-0390-1 .

[Quelle_15-9] A ^b Albert Serlo: Guide to mining science. First volume, fourth revised and up to the most recent edition supplemented, published by Julius Springer, Berlin 1884

[Quelle_5-10] 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

[Quelle_11-11] ↑ ^a ^b ^c ^d ^e ^f ^g ^h ⁱ ^j F. Freise: Alignment, installation and mining of hard coal deposits. Publishing house by Craz & Gerlach, Freiberg in Sachsen 1908

[Quelle_12-12] Emil Stöhr: Catechism of Mining Studies. Lehmann & Wentzel bookstore for technology and art, Vienna 1875

[Quelle_6-13] ↑ ^a ^b ^c ^d ^e ^f ^g ^h ⁱ ^j F. Heise, F. Herbst: Textbook of mining studies with special consideration of hard coal mining. First volume, published by Julius Springer, Berlin 1908

[Quelle_13-14] Christian Mues: Development of an extraction and expansion system for underground mining. Approved dissertation, Clausthal University of Technology, Clausthal 2008, pp. 13-14

[Quelle_3-15] ↑ ^a ^b ^c ^d ^e ^f G. Köhler: Textbook of mining science. 2nd edition, published by Wilhelm Engelmann, Leipzig 1887

[Quelle_4-16] 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

[Quelle_19-18] Dr.-Ing. Erich Lewien, Peter Hartmann: Technology of mining . Ed .: University of the German Trade Unions "Fritz Heckert". Fachbuchverlag, Leipzig 1958, p. 88 .

[Quelle_17-19] Collective of authors: Basic Geological Knowledge . Ed .: Horst Roschlau, Hans-Joachim Haberkorn. 2nd Edition. German publishing house for basic industry, Leipzig 1977, p. 146 .

[Quelle_18-20] Horst Roschlau, Wolfram Heinze: Knowledge storage mining technology . Ed .: SDAG Wismut. 1st edition. German publishing house for basic industry, Leipzig 1974, p. 233 ff .

[Wissenspeicher_BT-21] Georg Spackeler, Waldemar May: Mining Studies . 8. Dismantling lesson III. Ed .: Main Department of Distance Learning at Bergakademie Freiberg. 2nd Edition. Deutscher Verlag der Wissenschaften, Berlin 1957, p. 8 / 13-8 / 20 .

[Anm._Cramm.-17] A weather overburden is a mine that is built in the seam from bottom to top and is used for ventilation . (Source: Tilo Cramm, Joachim Huske: Bergman language in the Ruhr area. )