Dam (mining)
In mining, a dam is an underground structure that serves to separate a part of the mine from the rest of the mine. The separation can have various reasons, in addition to weather- related reasons, fire protection reasons can also play a role. Dams are also needed to protect against water ingress or explosions .
Basic structure
A dam consists of two retaining walls and the dam core contained therein. The purpose of the dam determines its dimensions, the material used and the equipment required. Openings, so-called manholes , are built into the dam for ventilation or access , depending on the requirements . Dam pipes, which are stable sheet iron pipes with a diameter of 700 mm and a length of 2000 mm, are used for this. If necessary, the pipes can be closed with screwable covers. In the front support wall facing away from the old man , several compression pipes are installed, each equipped with a slide or a quick-closing valve. The dam core is filled with liquid dam building materials, for example anhydrite , through these press pipes . Another variant is to wall the dams with shaped stones.
Another possible construction consists of several layers of reinforced shotcrete. This type of construction is particularly advantageous for water and weather dams, since profile irregularities can easily be compensated for by the shotcrete and any desired thickness can be achieved by increasing the number of layers in order to meet changing requirements. Water dams in shotcrete construction can be up to 10 m thick and withstand a pressure of several 100 m water column. Such special pressure dams are monitored with geomechanical sensors ( monitoring ).
species
Depending on the structure and use, the miner differentiates between the following types of dams:
- Fire dam
- Water dam
- Track dam
- Closing dam
Each of these dams is built according to its use and requirements.
Fire dam
A fire dam is erected in the event of an underground fire to seal off the weather path from or to the source of the fire. The miner differentiates between three types of fire dams:
- Rapid dams
- Pre-dams
- Main dams
Rapid dams are barriers that are designed so that they can be erected quickly. They serve to interrupt the weather management in the fire area as far as possible. Rapid dams are mainly built from fire dam cushions, which are cuboid balls made of rock wool, which are surrounded by a wire mesh. So that high-speed dams can be erected immediately, the material required for this is stored underground so that it can be used immediately in an emergency.
Front dams are significantly thinner than the actual main dam. They are created so that there is protection against possible explosions until the main dam is completed. In addition, they quickly interrupt weather management. They are usually built from stones or poured from thin quick-mix concrete shells.
Main dams are solid dams and constructed like closure dams. In the case of a fire area, they are used to finally close the fire area. To take fire gas samples, these dams are equipped with a sniffer tube, which is a DN 50 pipe with a shut-off valve, which is used to take weather or fire gas samples from the dammed mine construction. In addition, the main dams will be provided with a dam pipe to enable access to the mine field after the fire has gone out.
Water dam
Water dams are built to protect the mine building, which is still in use, from inflowing water from the castings. They can be installed in routes as well as in shafts . The composition and the water pressure of the mine water must be known in order to build an effective water dam. The two parameters are decisive for the type of dam construction and the composition of the dam construction material.
Track dam
Route accompanying dams are for securing the Streckensaumes in degradation routes in the face end region incorporated. They reduce the phenomena of convergence in mining stretches , making it possible for stretches to be used for double use. The dams are made from various building materials and are either rigid or flexible to a limited extent, depending on the building material. The dam building material is pressed into bullflex hoses, which are special hose-like sacks, or filled behind special formwork walls to create the dam along the route . Serious accidents can occur if the road embankments are incorrectly constructed.
Closing dam
For example, a section of the dammed-up pit is to be permanently closed with a closing dam . The closing dam is created in such a way that it separates the dammed mine structure tightly and tightly from the rest of the mine field. This prevents polluted weather or even firedamp from escaping. The closure dam also prevents creeping weather from entering the dammed area, thus preventing spontaneous combustion fires. In order for a dam to be able to perform these tasks safely and permanently, it must have a special structure. Between two retaining walls made of fully jointed stone, mortar, concrete or wooden walls, it also has a dam core made of solids, for example mountains , mortar or concrete . In addition, the dam is grouted with special setting materials after it has been built.
Categories for closing dams
From a weather point of view, dams can be divided into three categories:
- Retracting embankments
- Extending closing dams
- Closing dams with changing pressure gradient
When closing dams are drawn in, pressure fluctuations such as opening or closing weather doors do not affect the direction of the pressure gradient in the dam. Even with fluctuations in air pressure, the direction of the pressure drop always remains in the direction of the dammed mine construction.
With extending dams, the pressure gradient is always directed towards the open pit building. This does not change even if the air pressure fluctuates or if weather doors are opened or closed.
In the case of closure dams with a changing pressure gradient, the direction of the pressure gradient in the dam changes, depending on the air pressure, either in the direction of the insulated mine or in the direction of the open mine building.
Individual evidence
- ^ A b c d e f g Walter Bischoff , Heinz Bramann, Westfälische Berggewerkschaftskasse Bochum: The small mining dictionary. 7th edition, Verlag Glückauf GmbH, Essen 1988, ISBN 3-7739-0501-7 .
- ^ Heinrich Veith: German mountain dictionary with evidence. Published by Wilhelm Gottlieb Korn, Breslau 1871.
- ↑ a b c Gustav Köhler: Textbook of mining science. 6th improved edition, published by Wilhelm Engelmann, Leipzig 1903.
- ^ A b Fritz Heise, Fritz Herbst: Textbook of mining science with special consideration of hard coal mining. First volume, fifth improved edition, published by Julius Springer, Berlin 1923.
- ↑ Guidelines on the explosion-proof damming of abandoned mine structures (accessed on September 3, 2012).
- ↑ Operating recommendation for the ventilation and monitoring of dams (accessed on September 3, 2012).