driftway

A driftway is a horizontal or near-horizontal tunnel driven through the host rock or ore body of a mine, connecting the main shaft to working areas or linking different sections of the mine. Unlike a shaft, which runs steeply at angles of 60 to 90 degrees, a driftway follows the lie of the ground and the ore seam itself, making it the primary arterial passage through which personnel, materials, and extracted ore move. In hard rock mines, driftways are often driven along the boundaries of the ore body; in coal mining, they follow the seam.

The dimensions of a driftway depend on traffic and haulage needs. Typical widths range from 12 to 20 feet (3.6 to 6 metres), with heights of 8 to 12 feet (2.4 to 3.6 metres) in hard rock operations. A coal driftway may be narrower: 10 feet wide by 6 feet high if only person trips and conveyor belts are used. The walls and roof are supported by timber props, rock bolts, shotcrete, or steel sets, depending on the rock quality and depth. In weak strata, driftways require substantial timbering; in sound granite or competent sandstone, bolt patterns alone may suffice.

A driftway is distinguished from other horizontal passages by its role and permanence. A stope is an extraction chamber; a level or gallery is a working platform at a fixed elevation; a crosscut connects different levels or drifts at right angles. The driftway is the main trunk line, often the only passage for several hundred metres, and so its condition directly affects productivity and safety across the entire mine. Collapse of a driftway can trap personnel and halt all operations in the affected section.

Hazards and Maintenance

Common problems in driftways include ground pressure (where the surrounding rock slowly squeezes the passage), water inflow from fractures or overlying aquifers, and dust accumulation if ventilation is poor. Driftways in deeper mines experience higher stress; some are periodically relined with shotcrete or left wider than necessary to allow for eventual crushing. Regular inspection of the roof and walls is standard practice, and any significant sagging, cracking, or seepage triggers support upgrades before the passage becomes impassable.

The term driftway is used chiefly in North American and Australian mining; British and European usage more often simply calls it a drift or level drive. Historical driftways, particularly in coal mines, were often driven uphill at a slight grade (2 to 5 percent) to aid drainage of water seeping from above; this practice is less common in modern hard rock mining where pumping handles dewatering. The driftway remains the backbone of any underground mine layout and is typically the most heavily reinforced passage in the mine after the main shaft.