panel

A panel is a rectangular section of a coal seam marked out for extraction, bounded on all sides by unmined coal or supporting pillars. In room-and-pillar mining, the most common method used in underground coal mines, the seam is systematically divided into these geometric units before work begins. Each panel typically measures hundreds of feet on a side and extends the full height of the mineable coal bed, with dimensions set during mine planning based on roof stability, coal thickness, and equipment capacity.

The pillars separating adjacent panels are intentionally left unmined to support the weight of overlying strata and prevent catastrophic roof collapse. Panel size and pillar dimensions are calculated together: a larger panel requires thicker pillars, while thin pillars demand smaller panels. The ratio of extracted coal to retained coal in pillars (often expressed as a percentage of coal recovery) determines the economic viability of the mine and the long-term stability of the workings.

Panel extraction and retreat mining

Mining typically advances from the boundary of the panel inward, with continuous miners or longwall equipment extracting coal while roof support systems (temporary timber or hydraulic props, then permanent or temporary bolting) stabilize the immediate roof. Once the panel reaches its predetermined limit, miners execute "retreat mining," systematically removing the supporting pillars from the deepest point back toward the entrance. As pillars fall away, the overlying rock settles and compacts, with controlled subsidence allowing safe extraction of additional coal.

Panel geometry varies with mine conditions and equipment. Eastern U.S. coal mines often work panels 150 to 400 feet wide and 1000 to 3000 feet long, while western surface mining creates different extraction patterns entirely. Gassy seams or weak roof shales may require smaller panels to manage ventilation and ground control, whereas thick, stable coal allows larger panels and higher recovery rates.

The term reflects the orderly grid system imposed on the seam: the coal bed becomes a patchwork of panels like floor tiles, with pillars as the grout lines holding the structure. Poor pillar design or unexpected geological conditions (faults, weak coal, water intrusion) can trigger pillar failure, bumps, or loss of control during retreat, making panel layout a critical engineering decision that balances immediate production against long-term safety and resource recovery.