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How does room-and-pillar mining create support for the roof of a coal mine?
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coal mining
Schematic diagram of an underground coal mine, showing surface facilities, access shafts, and room-and-pillar and longwall mining methods.
In room-and-pillar mining, support for the overhead strata of earth and rock is created by leaving behind thick pillars of coal in a grid formation. This pattern is established by driving a series of parallel entries into the coal seam and connecting them at regular intervals with wider entries called rooms.12
While these coal pillars provide the primary structural support for the mine's roof, additional measures are used to ensure safety at the production face and within the entries:
- Roof Bolting: In modern mechanized mines, this is the most common method for supporting the immediate roof. Steel bolts are inserted into holes drilled into the roof and secured by resin or friction.3
- Additional Systems: For entries such as mains, submains, and panels, miners may use temporary or permanent supports, including hydraulic or friction props, cribs made of timber or reinforced concrete, and yieldable steel arches.3
The design of these pillars is critical, as they must be sized appropriately to handle the pressure of the overlying strata, especially as mining depth increases.13