A day in the mine

The miners’ work day begins, before every shift, in the changing area known as the “coop”, where they get undressed, hang their clothes on hooks and pull a chain attached to the ceiling where their work clothes are “waiting”. On the way to the shaft elevator they pick up their personal equipment – in the lamp room they put on their mining lamps and breathing apparatus, which will provide a miner with up to 50 minutes of oxygen in an emergency. The colour of the miners’ helmets indicates the jobs they do: supervisors wear white helmets, fitters wear blue ones and electricians wear green headgear. The workers who work on extracting salt wear yellow helmets, the mine rescue team wear luminous red helmets, and the men responsible for security-related matters wear orange helmets.

At the shaft head the miners wait for the elevator, which will swiftly carry them several hundred metres down into the depths of the mine, at a speed of approximately eight metres per second. The shaft is not only a means of transporting men underground – the transport shafts for teams and equipment also supply the mine with fresh air, known by the miners as “mine ventilation”, without which neither men nor machines would be able to work. Next to the shaft head there is an elaborate system for drawing in and circulating fresh air throughout the mine. The ventilation engineer is responsible for supervising the system and carrying out calculations to ensure that the miners can work in a well ventilated environment despite the running motors of the machinery.

An extensive network of passages

Once they have arrived at the shaft bottom in the depths of the mine, the miners leave the elevator and board vehicles which take them to their workstations at the salt face. Some reach their destination quickly, while for others the journey can last up to half an hour, depending on the size of the mine and how far individual faces are located from the shaft. The vehicles run along salt roads, whose surface resembles a normal street, through an extensive labyrinth of passages. The passages are from 12 to 16 metres wide and vary in height depending on the deposits and their cross-section. There are both level sections and up and down gradients, which are quite steep in places. The vehicles pass petrol stations, workshop areas, measuring stations where the content of reusable material in crude salt is measured, and conveyor belts measuring several kilometres which transport excavated crude salt to the shaft. Every now and then they pass new passages, which are interspersed with salt pillars. The pillars have an edge length of up to 50 metres and support the “overburden”, the several hundred metres of rock strata bearing down on the mine. The supporting pillars are large enough to be able to carry three times the load that actually rests on them.

Specialists at work

After their journey through the dark, partially lit passages, which are equipped with signs to better direct and regulate vehicle traffic, the miners arrive at the salt face. The temperatures here remain at a comfortable level (more than 20C), while air humidity is only around 20 per cent – this makes the miners thirsty! Every miner must therefore bring enough to drink. They also need food, as they have to endure an entire shift underground, about seven hours. After the foreman, the miners’ supervisor, has inspected the salt face and the progress of the work, the men are assigned their tasks. They perform their work largely independently and thus shoulder great responsibility for their work area.

Each miner has a specialisation. One drills holes with large, complex machines (large holes and blast holes), which the blasting technician then primes with explosive material complete with detonators. This is a considerable task as the driller bores 60 holes with a diameter of 35 millimetres seven metres deep into the rock. A computer-controlled blast hole drilling vehicle is used to do this - a precision machine which lays out the blast holes according to a set plan. The charges are detonated between shifts, when one shift is being carried away from the salt face and the next is waiting for the shaft elevator to bring them underground, from a control console.

Safety first

After the detonation, load transport vehicles take the crude salt away from the face. These are large, diesel-powered trucks (though some are electric) with shovels, which can hold up to 20 tonnes of salt (“excavated material”) at a time. The salt is delivered to the tipple, where the lumps of salt are quickly ground up by a crushing machine, which is equipped with a roller fitted with chisel heads. The ground salt is then carried to the shaft on a conveyor belt or to an interim storage facility in an underground bunker near the shaft.

K+S puts safety first, so the roof and side walls are constantly reinforced and stabilised, a process which miners call “scaling”. Using scaling machines, rock fragments often weighing a tonne that have come loose on the mine roof or walls are carefully detached so that they do not fall off unexpectedly and cause major damage.

The roof anchor drilling truck then drills holes for roof anchors – threaded rods up to 1.2 metres in length with an expanding sleeve at the tip, which like an oversized dowel binds the salt layers together and gives them a greater degree of stability.

Precise coordination

Since all the tasks carried out in the mine complement each other, every “move” must fit the overall plan, because only when one part of the work is carried out as planned can the next step be successfully completed. Although miners are specialists and largely work independently, ultimately they form a team which can only operate successfully and extract the required quantity of salt through efficient cooperation.

While one shift is being transported away from the face, the next is already waiting to take its place. Meanwhile, dust and blast fumes several hundred metres deep from the recent detonation disperse. Again the responsible foreman inspects the face to see if it can be worked, and again the miners transport tonnes of salt in wheeled loaders to the crushers and prepare and secure passages. The salt face, the area in which salt is blasted out, is thus pushed forwards, while the network of underground passages is automatically extended. The conveyor belts that carry the salt away from the face must be extended or reconstructed.

Computer-controlled vehicles in salt mining

The image of a miner with a pick and shovel has long been obsolete. Miners in potash and rock salt mines are now supported by computer-controlled machinery, which is essential to allow millions of tonnes of rock and raw salt to be extracted year after year, which are then processed into various salt, fertiliser and industrial products. Every person employed in K+S Group’s mining operations has a solid education behind him enabling him to perform his work independently and with a strong sense of responsibility for both man and machine.

 

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