Bord and Piller Method – 2

1. The sudden release of elastic strain energy stored in the pillars results violent burst of coal pillars is called?

2. In deciding the size of the panel the important factor to be considered is?

3. With strong roof and unyielding floor tends to?

4. Shuttle cars are the transporting media for ?

5. For designing pillars.....is used?

6. The width of the headings in bord and pillar method of working depends on?

7. The shape of the pillar that gives maximum percentage of recovery with speed reduced amount of lift for loading is?

8. The method suitable for workings seam under the surface containing valuable property water bodies for whose protection some coal is left unworked is?

9. In a seam with locomotive haulage system the junctions with main headings are staggered ?

10. Headings advancing in a direction at right angles to the main cleat are called?

11. The percentage of extraction of coal from a pillar of 30m x 30 m center to center with roadways 4m wide is ?

12. For given perimeter the greatest area of support is offered by ?

13. The number of panels to be opened at a time is decided by ?

14. Heavy roof fall and even premature collapse may taken place if line of goaf is?

15. The limiting depth for the bord and pillar mining is?

16. In shallow seams to prevent breathing of air to the depillared area through cracks to the surface the cracks have to be blanketed with a minimum thickness of layer of sand or earth nearly?

17. The minimum factor of safety in design pillar in bord and pillar mining?

18. The method suitable for working seam under the workings of another seam which is water logged or on fire is?

19. The first indication of roof weighting for regular fracturing roof in goaf is?

20. The shape of the pillar in steep seams for haulage and loading and in flat and inclined seam for adoption of high capacity machinery like shuttle cars and locomotive is ?

21. The daily advance in development of galleries by continuous miner?

22. Maximum roof exposure for stowing is?

23. Overriding of pillars and stooks and premature collapse in the depillaring area is due to presence of?

24. Maximum roof exposure for caving is?

25. While working seams steeper than 1 in 4 except the haulage dip the cross connections between the levels should be?

26. Heading advancing parallel to cleats are called?

27. The maximum compressive strength of cavable roof?

28. The groove made by coal cutting machine is called as ?