Bord and Piller Method – 1

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

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

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

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

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

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 During depillaring if the roof is laminated local fall occurs ....hours after the props are withdrawn?

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

24. 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?

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

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

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

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