Coal Mining – Mechanized Room and Pillar Mining

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The most common method of mining started with driving tunnels, and then intersecting these with “cross cuts” through the pillars of coal left to hold the roof (the top half of the cake) in place. As I showed in an earlier illustration (above), since it was easier to mine from free faces then the solid, the initial rooms driven were often widened, until the roof fell in. And, over time mining practice came to narrow those initial tunnels to around 10 – 15 ft in width. They were initially smaller, when hand won, but with the advent of more mechanized mining the width grew greater, and required more support in the tunnel itself to hold the roof immediately above.

At the same time, as the mine workings moved away from the shaft (which took coal out of the mine, but also supplied fresh air to it) it became more critical to steer the air entering so that it reached the working areas of the mine, and then could be sent back to the surface. Without that proper circulation of air, the gasses which the coal would give off, including methane (natural gas, carbon dioxide and carbon monoxide) this could well be fateful. And so the miners began to also build temporary or permanent “stoppings” or walls across some of the abandoned tunnels to steer the air currents down the tunnels in and out of the working area. To separate the two flows (in and return) between the main roadways permanent “airlock” types of walls would be built with doors between so that one could cross from one passage to the other without interfering with the passage of the air.

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