pillar extraction वाक्य

उदाहरण वाक्य

1. In 1954 mechanical pillar extraction of coal commenced at Scarborough.
2. No pillar extraction occurs, and the mine design is conservative to prevent surface subsidence.
3. Much of the city, particularly the northern portion, has been undermined by room and pillar extraction of coal that took place in the 1800s.
4. In the late 1990s, production from the Mount Isa original Mount Isa ore bodies began to drop, with copper ore production from the upper ore bodies falling from five million tonnes in 1994 to approximately 3.5 million t / y by 2000 because of increased dependence on pillar extraction sequences and increased reliance on truck haulage.