Rock Mechanics and Roof Supports

1. For equal resistance to crushing and bending the prop should have dia..?

2. A timber prop is expected to support an area of about.....all round?

3. The timber prop available max height up to..?

4. The depression of ground surface and the structures is called?

5. By tapering the prop at the foot or top by providing a lid on the top of the prop.....could be obtained?

6. Hand packing is useful up to max gradient?

7. In roof stitching the face should not be advanced more than ....m from the last tensioned rope?

8. The anchorage support of resin capsule is?

9. The anchorage support of the roof stitching is ?

10. The weight of the rocks in coal mining areas exerts a pressure nearly per metre depth from the surface is..?

11. Freshly exposed roof after blasting is effectively and quickly supported by..?

12. Bulk strength of the timber prop is ...(kg/sq.cm)?

13. The immediate roof is called..?

14. The yielding props which exert resistance with continuous increase in yield are called?

15. The load on a prop when upper member begins to slide is called?

16. The best method of mining for controlling the subsidence is..?

17. L/W faces with caving have caused difficulties in roof control at a depth of less than nearly..?

18. If the prop has to be set on loose ground it should be placed on a flat base piece having thickness not less than..?

19. The rocks are said to be flaggy if the bedded planes are separated by..?

20. Crushing strength of sandstone is..?

21. Compressive strength of coal is..?

22. In resin capsule the mixture hardens within .... seconds and becomes solid?

23. For testing a specimen in the laboratory the length:dia ratio should be?

24. The load at which an axially loaded prop reaches its elastic limit or at which it begins to buckle is called?

25. On account of the weight of the rocks the pressure arch is transmitted to abutment if the depth of coal seam is ....the length of the pressure?

26. The max gap between two chock shield supports is..?

27. The phenomena of lifting up of the floor if the floor is weak is called..?

28. If the bedded planes are separated by more than 1.2 m apart then the rocks are said to be?

29. The number of props required to support one square meter of the roof area is?

30. The pressure arch in L/W workings has its apex or crest at a min height above the seam at nearly .... times the length of face?

31. The inclination of prop to the vertical when set to side support is?

32. In hydraulic oil the % of emulsion oil is?

33. The maximum height of the roof that can be tested by bamboo?

34. Phenomena of the rocks in immediate roof bending downwards under their own weight and tend to separate from one another is known as..?