DIVISION OF LEVELS BY SUB-LEVELS

LEVEL : Horizontal road way driven parallel to strike

SUB LEVEL:

·         Sub level is a road way driven parallel to strike direction  in between two main levels

·         Sub level divide the block or pillar formed during development in to horizontally two slices

·         Sub levels are driven when the thickness of the ore block is more

·         Block thickness more than 20meters

·         Blocks formed in longitudinal and transverse direction

·         Sub levels are driven at regular intervals between two main levels

·         Dividing the block in to slices

·         Driven for easy stoping operation

·         Drivage of sub level carried out before starting of stoping operation

·         Drifts , ore passes, ramps are connected to sub levels and main levels

PURPOSE OF SUB LEVELS

1. ·         For Passing adequate ventilation
2. ·         To Obtain more production
3. ·         To For access in to stoping area
4. ·         For inspection
5. ·         To reduce number of supports
6. ·         For easy extraction
7. ·         For sampling of ore
8. ·         Used  as intake and return air ways
9. ·         Used as haulage road ways
10. ·         Used as travelling road way
11. ·         Used for transport of mineral
12. ·         Carries water pipe lines
13. ·         Carries electric power cables

SIZE OF SUB LEVELS

1. ·         Size of sub level should be such that it should provide ample space for
2. ·         Movement of machinery
3. ·         Passing ventilation with least rubbing surface
4. ·         Without congestion
5. ·         Width generally 3 – 4.8m
6. ·         Height 1.2 – 3m
7. ·         If mechanization desired the dimensions are 4.3mx3m
8. ·         Maximum width of sub level permitted by law 4.8m
9. ·         Maximum height of sub level permitted by law 3m

FACTORS DECIDING THE SUB LEVELS

1. ·         Thickness of ore body
2. ·         Condition of walls
3. ·         Condition of ore body
4. ·         Reach of drill machione
5. ·         Level interval
6. ·         Length of back
7. ·         Strike length of block
8. ·         Requirements of ventilation
9. ·         Loading facilities
10. ·         Cost of drivage