untertage

Untertage is the German term for something located beneath the surface of the earth. In mining, Untertage refers to underground mining activities, as opposed to Tagesbetriebe (open-pit or open-cast operations). The term is used in mining engineering, geology, and safety to distinguish subterranean work from surface extraction.

Historically, Untertage mining developed with the construction of vertical shafts and horizontal tunnels to access ore bodies and coal seams. The introduction of mechanized drilling, blasting, and raised bore equipment in the 19th and 20th centuries increased efficiency, but also heightened the importance of ground control, ventilation, and gas management.

Common underground mining methods include room-and-pillar (Kammer-Pfeiler-Abbau), longwall mining, and sublevel stoping. Room-and-pillar leaves pillars to support the roof; longwall uses a moving hydraulic support system to remove a panel and allow roof collapse behind the face; sublevel stoping excavates across sublevels with backfill. Supporting the roof and controlling ground movement rely on rock bolts, shotcrete, and steel arches.

Access is provided by shafts (Schächte) or declines and adits (Stollen). Ore or coal is transported via conveyors, underground trains, or skip hoists. Ventilation systems extract exhausted air and supply fresh air, while drainage and pumping manage water inflows. Power and service lines run along tunnels and in dedicated ducts.

Underground operations pose hazards such as rock bursts, gas inflows (notably methane), water inrush, and long-term subsidence. Regulations require risk assessment, continuous monitoring, emergency plans, and professional training. After mine closure, reclamation and monitoring programs aim to stabilize surfaces and reduce environmental impact.