| 11. | Coal was extracted by room and pillar working in the Black and White mine and longwall mining in the Trencherbone.
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| 12. | Mine voids in the inclined slope resulted from the practice of room and pillar mining during the early 20th century.
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| 13. | The mines are located in Lea and Eddy counties, New Mexico, and are operated by the room and pillar method.
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| 14. | It was constructed using the room and pillar technique, where pillars of dolostone have been left to support the overlying rock.
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| 15. | Pink areas were a room and pillar mine at the time of the disaster, while retreat mining had been completed in the brown areas.
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| 16. | Stone was extracted by the " room and pillar " method, by which chambers were mined, leaving pillars of stone to support the roof.
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| 17. | Room and pillar mines are developed on a grid basis except where geological features such as faults require the regular pattern to be modified.
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| 18. | Much of the city, particularly the northern portion, has been undermined by room and pillar extraction of coal that took place in the 1800s.
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| 19. | It has a grid of high, wide tunnels separated by square limestone pillars created by the room and pillar method of hard rock mining.
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| 20. | Quarrying is done using the room and pillar method, mining only half of the salt and leaving the remaining half to support what is above.
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