Bord and pillar is the oldest and still the most widely used method of underground coal mining in India. The idea is simple: instead of removing all the coal at once, miners cut a grid of tunnels through the seam and leave large blocks of coal standing in between. The tunnels are the "bords" (also called galleries or roadways) and the untouched blocks are the "pillars". Those pillars are not waste — they are structural columns that hold up the rock above while people and machines work below.
The method runs in two broad phases. The first is development. Working the seam like a chessboard, miners drive a regular pattern of galleries in two directions, leaving square or rectangular pillars between them. Development opens up the district, provides roadways for transport and ventilation, and proves the coal. Because only a fraction of the coal is removed at this stage, the ground stays comparatively stable and the roof is easy to keep up.
The second phase is depillaring, or pillar extraction. This is where most of the coal is actually won. Working in retreat — from the far boundary back toward the shaft — miners cut into the standing pillars and take the coal out, usually reducing each pillar to a small stump or removing it entirely. As support is withdrawn, the roof behind the working line is deliberately allowed to cave into the void (the "goaf"). Depillaring is the more demanding phase because the strata are being disturbed, so it is planned carefully and carried out under close supervision.
Keeping the roof up is the central engineering problem, and it is handled through strata control. Immediately after a roadway is cut, the exposed roof is secured — historically with timber or steel props, and in modern practice most often with roof bolts that pin the weak, layered rock into a stronger self-supporting beam. Roadway width, pillar size and the depth of cover are all designed together so the pillars can carry the load without crushing. During depillaring, movable powered or friction supports protect the immediate working area while the goaf caves safely behind it.
Bord and pillar suits Indian coal for several practical reasons. Many Indian seams — including those of the Jharia Coalfield, developed in the Gondwana Barakar Formation — sit at moderate depth, vary in thickness and are cut by geological disturbances such as faults and dykes. Bord and pillar copes well with irregular ground because each district can be laid out to follow the coal, and development can stop or step around a disturbance without abandoning the whole panel. It needs less heavy capital than fully mechanised longwall systems, adapts to variable roof conditions, and lets operators recover coal in two stages so a district earns during development and again during depillaring.
Its trade-off is recovery. Coal left permanently in pillars is coal not sold, so a well-run mine aims to recover as much as it safely can during depillaring while leaving barrier pillars where they are needed to protect shafts, roadways and surface features. Balancing recovery against safety and stability is the everyday judgement at the heart of the method — and the reason bord and pillar remains the backbone of underground coal mining in India.
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