Bord and Piller Method – 1

1. If the pillars are not strong they may be crushed due to sudden pressure is called?

2. Main fall occurs When the area of extraction is nearly equal or more than the .....of the depth?

3. If the depillaring is proceeding from dip to rise and seam inclination is not mild so that goaf can be submerged in water then the line of goaf is?

4. The gradient in the cross cut should not be less than?

5. During extraction of coal the minimum thickness of the coal(rib) is left against the goaf is?

6. The average number of faces in a district if the number of headings is 'N'?

7. The fall which takes place soon after withdrawal of supports is called ?

8. The minimum thickness of the coal seam for adopting Bord and pillar method of mining?

9. The pillar is splitted into 2 or more stooks if the pillar size is more than?

10. Upto what gradient the Bord and pillar mining can be adopted without special arrangements?

11. Coal mine operations are prohibited if the common boundary is within?

12. During development the height of the gallery should not exceed?

13. Once the pillar extraction is commenced the splitting is of pillars may be done upto.....pillars ahead of the pillar is under extraction?

14. In which line of extraction one solid stook intervenes between two stooks under extraction at a time?

15. A face or working place which is parallel to the main cleat is said to be?

16. Coal mine operations are prohibited if the cover is less than?

17. The minimum distance between two sections should be if one is working at floor and one at the top?

18. During depillaring if the roof is laminated local fall occurs ....hours after the props are withdrawn?

19. The galleries driven through the pillar for forming stooks are called?

20. The pillars formed during development are split into small pillars are called?

21. The critical width of extraction at which the subsidence at the bottom of the trough has a maximum possible value is?

22. Coal seams are said to be contiguous if the two seams are separated by a parting of less than?

23. The water-bearing quality of a seam is measured by the?

24. Drivage of two sets of roads and forming of pillar is known as?

25. In which line of extraction the pillar or stook is under excessive pressure and is liable to crush?

26. In Indian mines the ratio of the quantity of water pumped from underground workings to the quantity of coal produced varies?

27. Working coal in the pillars formed in the operation in bord and pillar mining is?

28. With a good sandstone roof the area exposed may not more than .....sq.m at one stook extraction and ......sq.m if 3-4 stooks under extraction?