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Methods of Underground Coal Mining

HER: High Extraction Retreat

A disadvantage of most room-and-pillar methods is that so much coal is left behind in the pillars. So miners must have been thinking, "Suppose we just left little "stumps" or "fenders" instead of whole pillars; we could get a really high rate of extraction and then make a hasty retreat before the whole thing caves in."

High-extraction retreat mining is a form of room-and-pillar mining that extracts most of the coal. Rooms and pillars are developed in the panels, and the pillars are then systematically removed. Rows of chain pillars are along the panel boundaries, as is the case in longwall mining. Panels are 400-600 feet wide, and extraction ranges from 70 to 90%.

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