Question

1. Given an underground total mining cost of $10.75 per tonne, surface mining costs of $3.85 per tonne of ore and surface mining stripping costs of $2.05 per tonne of waste, calculate the break even stripping ratio ( i.e. with zero profit) between surface and underground mining. That is, the point at which underground mining should be contemplated.   Explain and illustrate by means of a diagram the meaning of your answer.    (6 points)

please answer the question in detail with diagrams

Answer 1

stripping ratio is the ratio of the volume of overburden (waste material) required to be handled in order to extract some ton of ore.

stripping ratio= (overburden in ton )/ (ore extracted in ton )

let the stripping ratio be x:1

for underground mining stripping ratio is not important because overburden is not removed.

Overburden removal is important in surface mining, because upper waste material has to be removed to extract the underlying ore material.

Cost per tonne of underground mining= $10.75

surface mining stripping costs per tonne= $2.05

surface mining costs of per tonne=$3.85

cost per tonne of surface mining= {stripping ratio *(surface mining stripping costs per tonne )} +surface mining costs of per tonne

for break even

cost per tonne of surface mining =Cost per tonne of underground mining

substituting values

x*2.05 +  3.85 =10.75

x=(10.75-3.85)/2.05

x=3.366

so the stripping ratio = 3.366:1

that is 3.366 tonne of overburden should be there to reach a break even

This means for prefering underground mining over surface mining the sripping ratio should be 3.366:1