Backfilling (mining)

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In mining, backfilling is the term used to describe the filling of the void between the route extension and the mountains with suitable building materials. Different materials and techniques are used here.

need

When Drift excavation of the roadway cross section can not be absolutely uniform shot out or cut out. After the rock has been loosened, the rock surface is very irregular, so a cavity always remains between the warpage and the rock . The remaining cavities must be filled so that the expansion segments are loaded evenly. The load-bearing capacity of the extension is increased by evenly loading the extension segments. The type and necessity of backfilling depends on the stability of the mountain, the purpose of the route and the construction method used. Careful backfilling is necessary, particularly with sliding arch expansion , rigid arch expansion and ring expansion . The reason for this is the load on the expansion by the rock pressure . If the expansion is loaded and there are cavities behind the expansion, the expansion deforms by moving into the cavities. In coal mining, firedamp can also accumulate in these cavities ; here the backfilling prevents the accumulation of these explosive gas mixtures at the same time. However, the backfill can only fulfill its tasks if it encloses the extension of the route over its entire circumference and is directly connected to the mountain surface surrounding the extension.

Backfilling methods

Backfilling of the delay by means of rocks

There are different methods of backfilling. Either lumpy materials or backfill mortar are used as backfill materials. A dense and small-sized backfilling ensures that the expansion is evenly loaded. Special foam plastics are also used to fill larger cavities behind the track expansion.

Backfilling with lumpy materials

Backfilling with lumpy materials is the oldest form of backfilling. In the Harz mining industry, rock of various sizes was used to backfill the cavities behind the warpage, and these were carefully inserted. Backfilling with rock rock has the advantage that the backfill material accumulates when driving the road. However, there are not always enough rock rocks that are suitable for backfilling. For this reason, the backfill thickness is between 20 and 25 centimeters. Sudden pressure phenomena often occur in mining stretches. Due to its limited flexibility, the backfill acts like a pressure cushion, which keeps the pressure away from the expansion frame.

Mortar backfilling

By backfilling with mortar or shotcrete , a linear frictional connection of the extension to the rock surface is achieved. With this type of backfilling, liquid mortar is pressed into the cavities between the lining and the rock. The mortar is mixed on site in a backfill system and passed on with pressure. For this type of backfilling, a tight distortion is required. The tight distortion prevents the building material from passing through. In the area of the edge of the track , a track dam is usually built from Bullflex hoses filled with liquid mortar. In the past, these Bullflex hoses were also used when building tunnels to backfill the lining. The building materials used must have certain properties. The setting time is a few hours. Depending on the building material, sufficient ultimate compressive strength is achieved after just 24 hours. However, it is also often necessary to achieve the greatest possible early strength so that a support effect on the surrounding rock is generated quickly.

Individual evidence

  1. ↑ a b c d e f g Carl Hellmut Fritzsche: Textbook of mining science. Second volume, 10th edition, Springer Verlag, Berlin / Göttingen / Heidelberg 1962.
  2. ↑ a b c Ernst-Ulrich Reuther: Textbook of mining science. First volume, 12th edition, VGE Verlag GmbH, Essen 2010, ISBN 978-3-86797-076-1 , pp. 375–378.
  3. ↑ 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 .
  4. ↑ Werner Dürrfeld: Method and device for backfilling of the extension of the mining and tunnel construction with the help of a hardening filling having support tubes . Patent EP No. 63630, April 29, 1985.
  5. ↑ Bergbau-Forschungs GmbH Research institute of the hard coal mining association: Mechanization of the route expansion . In: Commission of the European Communities (ed.): Technical Research Coal, Luxembourg 1980, pp. 15-25.
  6. ^ Gustav Köhler: Textbook of mining science. 6th edition, published by Wilhelm Engelmann, Leipzig 1903.
  7. ^ A b Walter Bischoff , Heinz Bramann, Westfälische Berggewerkschaftskasse Bochum: The small mining dictionary. 7th edition, Verlag Glückauf GmbH, Essen 1988, ISBN 3-7739-0501-7 .
  8. ↑ European patent application: backfill mat. Online (accessed April 20, 2015).