Rock Mechanics and Roof Supports

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

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

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

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

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

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

7. Hand packing is useful up to max gradient?

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

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

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

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

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

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

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

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

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

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

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

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

20. The anchorage support of resin capsule is?

21. 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?

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

23. Crushing strength of sandstone is..?

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

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

28. The anchorage support of the roof stitching is ?

29. Compressive strength of coal is..?

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

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

32. The immediate roof is called..?

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

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