longwall retreating type of mining

См. также в других словарях:

• coal mining — Coal was very important in the economic development of Britain. It was used as fuel in the factories built during the Industrial Revolution and continued to be important until the 1980s. The main coalfields are in north east England, the north… …   Universalium

• Underground mining (soft rock) — refers to a group of underground mining techniques used to extract coal, oil shale and other minerals or geological materials from sedimentary ( soft ) rocks. Because deposits in sedimentary rocks are commonly layered and relatively less hard,… …   Wikipedia