20 m below the ground, the museum maintains a visitor mine constructed to resemble a real mine, with a network of about 2.5 km of tunnels. Here visitors can see the impressive mining machines from close up, get an idea of the trials of day-to-day work underground, and feel like real miners for a little while.
Our soon to be opened new highlight, a simulated shaft descent, will make this impression even more life-like.
Themed tour: coal mine
Most of the visitor mine is devoted to coal mining. The actual mining activities include the creation of mine structures and the extraction of coal: an underwater tableau shows how the blind shaft, which had become flooded since its construction, was manually deepened in the 1960s. Two kinds of tunnel driving are shown: excavation with a full-face boring machine and with drilling and blasting. Coal extraction can be found at two workings with a chain coal cutter and with pneumatic picks, and in three longwall workings or faces. The first of these shows the use of a coal plough to shear off slabs of coal, combined with individual props for roof support (1950s/1960s), the second shows a shearer loader being used to cut coal, in combination with self-advancing supports (1960s/1970s). The third face fills in the technological gap between then and the present with equipment such as the double-drum shearer loader and powered roof supports. These are typical of the German coal-mining industry today, where the average length of the longwall faces is 300 to 400 m. The coal-mine themed tour also shows numerous items of equipment with logistic and safety-related functions.
In the coal-mining industry, the pick or pickaxe, which had long been the main tool of extraction, was replaced in the 1920s by the pneumatic pick. From the mid-1950s the pneumatic pick was increasingly superseded by the coal plough and the shearer loader.
Today the pneumatic pick is only used for ancillary work.
In the complex tunnel network of an underground coal mine, many transport operations are carried out on railway tracks.
Today the locomotives are usually equipped with a diesel motor or an electric engine. In the past there were also benzene locomotives and compressed-air locomotives.
In the tunnel network of the visitor mine, which is around 2.5 km long, small electric locomotives are used for transport. One or two of these locomotives are usually to be found in the battery charging room, very close to the shaft.
The pneumatic hammer drill, in use since the beginning of the 20th century, constitutes a major advance in the making of blast boreholes, which used to be laboriously drilled by hand. The drill column, which is also pneumatically driven, bears the weight of the hammer drill and generates the pressure needed for drilling. To reduce the risk of black lung disease, the drilling dust is extracted by suction or suppressed using water. These days hammer drills are used in situations where the use of a drilling jumbo is not possible or expedient.
On this face, the coal is cut out of the seam by a shearer loader. It represents the state of technology from the mid-1960s to the mid-1970s.
The single-drum shearer cuts the coal out of the seam as it moves in one direction, and loads it onto the scraper chain conveyor with its rake blade on its return.
The hydraulic self-advancing supports, here in the form of support props, prevent the rock from falling down. Behind the props, the rock is allowed to collapse.
The first “Dahlbusch bomb” was built at the Dahlbusch mine in Gelsenkirchen in 1955. Here it was used to free three trapped miners, who could only be rescued through a drill hole.
The most famous use of a Dahlbusch bomb, known as the “Miracle of Lengede”, took place in 1963. In this mining accident, ten miners who had been trapped for two weeks were rescued with the help of the “bomb” – miraculously unharmed.
A similar rescue device was used to free 33 miners in Chile in 2010.
Compressed air lamp
In coal mines the lighting has to be constructed in such a way that explosive mixtures of air and firedamp (methane) cannot be ignited.
The compressed air lamp is particularly safe in this respect. It only works if its protective glass cylinder is intact and airtight. If this is the case the compressed air drives a small turbine generator, thus producing electrical energy. If the glass cylinder is damaged, the compressed air escapes and no electricity is generated.
Mine bicycles are often used by tradesmen, who have to be able to get to their workplace at any time. Blasters, who are not allowed to use the passenger train with their explosives, also make use of bicycles. The mine bicycles are usually equipped with a second seat. The seat without pedals is most popular.
High tech underground
The visitor mine took several years to construct. In this period, the museum’s miners removed 2500 m3 of rock, transported it to the surface, and excavated 100 m of new tunnels. Finally, around 27 powered roof supports, roughly 50 m of scraper chain conveyors, a double-drum shearer loader (cutting machine) and a continuous miner (tunnelling machine) were installed.
The result was a state-of-the-art longwall face, of the type generally to be found in the Ruhr today. Visitors can now see and experience a high-tech longwall face, the culmination of years of mining technology development.
The blasting section in the visitor mine shows the state of mining technology at the end of the 1950s. The main equipment used for this is the pneumatic drilling jumbo. The rotary percussive drill can be moved by means of the boom.
Working with this drilling jumbo is less physically strenuous, as it only involves control levers. The noise exposure is high, however.
The following tasks are repeated constantly: drilling of blasting holes, blasting, removing the debris, and supporting (securing) the newly created cavity.
The visitor mine’s 80 m long plough face, in a shallow, 2 m thick coal seam, reflects the state of technology for roof support, extraction and backfilling in the 1950s and 1960s.
Individual props support the roof (the rock above the coal). A coal plough slabs off the coal from the seam and loads it onto a scraper chain conveyor. The cavity behind the face is filled mechanically with rock (pneumatic stowing). The filling material reaches the pneumatic stowing machine through a central pipeline.
Chain coal cutter
The chain coal cutter was powered by a pneumatic motor and had a chain fitted with picks – similar to a chainsaw – with which it was able to cut a groove a few centimetres wide into the coal face.
For greater stability, the machine was clamped between the roof and the floor of the tunnel. The groove made it easier to loosen the remaining coal with the pneumatic pick.
Tunnel boring machine (“mole”)
Tunnelling machines are one way to create galleries in a mine.
“Full-face boring machines” are particularly effective; like the tunnel boring machine in the visitor mine, these cut a circular tunnel cross-section into the rock.
Extensive preparations are needed before such machines can be used. For example, they have to be assembled underground from individual components. This kind of tunnelling technology is therefore only worthwhile when particularly long galleries need to be excavated.
Tobias the mine horse
The mine horses were used for the transport of coal, rock and other materials. They usually remained underground for several years, and some eventually went blind. It is said that the mine horses were able to count: if more mine cars than usual were attached, the horses simply refused to move.
The last mine horse in the coal mines of the Ruhr district was called Tobias. He remained in service underground at the General Blumenthal mine in Recklinghausen until 1966.
The overhead monorail is a typical mode of transport in coal mining. It is mainly used near the working face, where no normal trains can travel.
The track of the overhead monorail is suspended from chains, so this system of transport is independent of the condition of the floor.
For shorter distances the main mode of transport used is pneumatically powered overhead railways (shunting trolleys). For longer distances, on the other hand, rope-hauled or self-propelling rail systems are more suitable, usually in the form of diesel trolleys.
The floors (the different levels of a mine) are connected to each other by sloping galleries or vertical shafts. A shaft which only connects two or more floors of a mine is called a blind shaft, because it doesn’t see the light of day.
In the recreated blind shaft in the visitor mine, the shaft gates can be opened and the swinging platform can be activated. When the platform has descended, wagons carrying materials can be pushed onto the pit cage, or people can enter the cage.
Themed tour: iron ore mine
The iron ore mining section shows how iron ore was extracted in northern Germany until the end of the 1970s, using the room and pillar system.
Between the rooms, part of the surrounding rock remains standing as a support.
One room shows how the ore is extracted by cutting, using a continuous miner. Three further rooms show extraction by drilling and blasting. Here self-propelling equipment is used: the drilling jumbo, the explosives truck and the loader use diesel motors to drive from one room to the next. In another room visitors can see a “part-face heading machine”, which cuts out the rock with its movable cutter head.
The drilling jumbo, manufactured by Hausherr, is equipped with a movable boom. The boom carries the drill, putting it in the right position to make the blasting holes. Blasting guidelines stipulate that these have to be around 3 m long and parallel; this is a prerequisite for a good blasting outcome, in which the cavity has the intended form and size after the blasting.
The continuous miner is a kind of part-face heading machine with a flat cutting boom which can be pivoted up and down and sideways. The cutting bits are mounted on rotating chains, making it possible to cut a rectangular tunnel cross-section. The rock is transported to the discharge boom via a conveyor device. The continuous miner moves on crawler tracks.
Double lateral chain scraper conveyor
The double lateral chain scraper conveyor is used to transport the blasted rock, i.e. the debris. It is very robustly built for this purpose. It consists of a line of steel conveyor troughs in which a continuous chain belt revolves. Drivers or scrapers mounted between the two chains on the outside push the rock from the loading point towards the discharge point. The power unit with electric motor and gear mechanism is mounted on the side at the discharge end.
Joy front-end loader
The front-end loader manufactured by Joy has an “articulated steering” mechanism between its two axles. This makes it very manoeuvrable, and able to handle very tight curves. At the front end the loader has its loading bucket, which digs into the debris with considerable force as the loader drives forward, and fills with rock. The loader than drives to the unloading zone with the rock. In contrast to the continuous conveyors (belt conveyors and scraper chain conveyors) this is what is referred to as shuttle haulage.
DThe scraper loader is a robust, versatile loader, which was in widespread use up to the 1960s. The rock which is to be removed is moved by a scraper bowl to the loading platform, where it is transferred by cable hoist to a scraper chain conveyor. The scraper bowl can be moved forwards and backwards by means of cables and rollers. Its weight makes it dig into the debris and fill with rock. Because of its construction, the scraper loader is also suitable for operation in places with steep gradients.
Part-face heading machine AM 50
The Alpine Miner type part-face heading machine has a cutting boom that can be raised and pivoted, with a transverse cutting head. This is fitted with bits which cut the rock out of the groundmass. A pincer-like device loads the cut rock onto a scraper chain conveyor, which ends behind the machine as a discharge boom. The crawler tracks increase the mobility of the part-face heading machine.
Unimog explosives truck
The explosives truck has a storage container at the back for loose, granular blasting material, a mixture of ammonium nitrate (AN) and hydrocarbons (C), e.g., chemical fertilizer and diesel oil, which is very safe to handle. This ‘ANFO’ (ammonium nitrate/fuel oil) explosive is blown into the blast holes through a hose pipe using compressed air. The compressed air needed for this is produced on the vehicle by an electric compressor. The explosives truck is equipped with a cable drum at the front to connect with an external power source.
The belt conveyor is a conveyor which is in continuous operation. It consists of a steel construction with belt rollers, over which a continuous rubber belt is moved. This rubber belt transports the rock and also serves to transmit power. The belt conveyor is less robust than a scraper chain conveyor. Thus the very coarse debris generated by blasting has to be crushed in a crusher first. The finer rock produced by the continuous miner, however, can usually be extracted straightforwardly without any further crushing.