Definition :- Stripping Ratio & Its Calculation

STRIPPING rATIO (s.r.) Stripping Ratio (S.R.) denotes volume of Over Burden (OB) required to be removed for obtaining one tonne of Coal. ...

STRIPPING rATIO (s.r.)

Stripping Ratio (S.R.) denotes volume of Over Burden (OB) required to be removed for obtaining one tonne of Coal.

1. Natural Stripping Ratio (S.R.)

R atio of OB in cubic meter that has to be removed for obtaining one tonne of Coal.

2. Average Stripping Ratio (S.R.)

The ratio of OB in cubic meter to be removed against total tonnage of coal obtained for a given property.

3. Peak Stripping Ratio

More than average Stripping Ratio (S.R.).

The difference between Peak and Average Striping Ratio indicates complexity of deposit.

*Formula of Stripping Ratio*

S.R. = Volume of OB (in meter cube) / Volume of Coal (in tonne)

**Importance of Stripping Ratio (S.R.)**

(i)   it is index of Open Cast Mine Planning.

(ii) if average is Stripping Ratio (S.R.) is known, then it is easy to workout, whether the property is Viable or Not.

** Factors influences the natural Stripping Ratio (S.R.) **

1. Seam Gradient
2. Variation in thickness.
3. Topography of the Area.
4. Multi seam, etc.

*Example*

Calculate Stripping Ratio, if seam thickness 10m, cover of OB is 35m for a patch 100m × 100m. Take a specific gravity of coal 1.40.

1. Volume of OB = l × b × h

= 100 × 100 × 35

= 3,50,000 meter cube  

2. Volume of Coal = l × b × h

= 100 × 100 × 10

= 1,00,000 meter cube 

Conver into tonne = Volume of Coal × Specific Gravity of Coal

 = 1,00,000 × 1.40

 = 1,40,000 Tonne (Te)

3. S.R. = Volume of OB (in meter cube) / Volume of Coal (in tonne)

= 3,50,000 / 1,40,000

= 2.5

= [ 1 : 2.5 ] 

1 - Coal in tonne : 2.5 - OB in meter cube 

*Selection of Opencast Mining Method*

1. 1:1.5 - Manual quarrying.


2. 1:2 - Semi Mechanized quarrying.


3. 1:3 to 4 - Bucket Wheel Excavator.


4. 1:4 to 5 - Shovel dumper combination.


5. 1:8 to 10 - Dragline.