From the fascinating “English Russia” web site:
“When you are 1500 feet deep, there’s no wind, there’s no ambient sound, and there’s no sunlight as well (no wonder!). However, ride on the elevator doesn’t take too long – during these seconds you virtually see your whole life in front of your eyes. The open cage whooshes downwards swinging around like crazy and your guts really seem to come all the way up to your throat!
When you’re out of the cage, you arrive to a small platform, where multiple tunnels are intercrossed. These tunnels are made for so called “taxis”, small diesel-powered vehicles that can transport 2 to 12 men, depending on their designation. The mine uptake is only a drop in the sea of shafts, since there are lots of tunnels, which lead to actual mining sites. The most distant longwall (which is the name of the place of actual mining) is 17 miles away from the elevator! The “taxi” drives at speed of 20-25 mph, so it takes quite some time for some miners to get to work.
Personally for me the biggest shock completely ruining my notion regarding salt mining was the fact that salt is actually mined not at the end of the tunnel. The harvester moves back and forth along its side! So the longwall gradually shifts towards harvested side in parallel to itself. The harvester has two cutting drums. The first one is located in front of the machine and intended for cutting the upper part of the wall. The second one is in rear and cuts the lower part. So now is the most interesting part. One passing cuts off about 10 to 20 inches of the longwall. That means that several approaches increase the width of the tunnel by good ten feet! In order to keep it from collapsing hundreds of hydraulic mountings are used. Every one of them can bare very many tons of pressure. Really many tons, I mean.
When the longwall’s width becomes too large, these mountings are gradually relocated towards the wall being cut. Rock layers behind the mountings simply collapse. Most of the time they collapse whenever they want, so, it can be rather dangerous. Danger lays in the fact that the collapse of a massive rock layer can create gigantic pressure. There was an accident, when a 200-pound metal table was thrown along the tunnel at distance of 250 feet. But such cases are rather rare, as a matter of fact. Regular kitchen salt, which is Sodium Chloride, is being produced on a small auxiliary enterprise. Overwhelming majority of the salt produced is Potassium Chloride, which is used mainly for fertilizers.”