Is there any information about the average stripping ratio of open pit mines around the world?
Dear Amir,
the question you are asking has no direct answer. At least to my knowledge there can be no average stripping ratio of open pit mines around the world, simply because we are talking about tens of thousands of open pit mines with limited knowledge for several of the smaller mines.
Additionally, the stripping ratio can be a dynamic parameter in a mine, changing over the years, depending on the cut-off-grade strategy and the overall mine planning of the project.
Even if there was an average of ALL open pit mines that would not offer any knowledge regarding open pit mining. The stripping ratio in a mine is chosen based on economics. A high grade orebody can support a high stripping ratio. A low grade ore body cannot support a high stripping ratio. Thus you may have a range of stripping ratios from 1:1 to 1:15 or even more.
There are too many parameters that determine the stripping ratio: price of commodity, CAPEX, OPEX, recovery rate, types of overlying geology, density and RQD are important and consequently the slope angle of the open pit as you progress downwards. You may also have water problems, etc.
Therefore you could have average stripping ratios categorised by commodity or other parameters but still that would not be representative.
Nevertheless, if someone else has some interesting information or data to offer I would be interested to know them.
Dear George Barakos
You are totally right. But I was hoping that a statistical survey might have been done in this regard.
Thanks for your answer.
Dear @Amir Khademian,
that is the reason why I mentioned I would be interested as well if someone had such information. However, my advise would be to make such a search per commodity. You might get some rough estimations in that case.
Difficult to have an average world-wide due to many many parameters involved. The two largest gold pits in Canada at the moment boast a similar waste/ore ratio of about 1.8 / 1.
I totally agree with George Barakos.
Even if there has to be an average stripping right across the world , it will totally affect the cost as well as the profit of each mine. The reason is that each mine is located in a different geographical location in the sense that the orientation of each deposit various as well as the depth at which the deposit is located.
So when doing analysis on the method of extraction, you will have to take into account the geological, geotechnical and economical aspects of the deposit and that will yield a SR that will be different from other open pit mines. Therefore, the stripping ratio is empirical.
Nonetheless, I would be interest to know if there is a research proven answer
We often would use of rule of thumbs but always dependent on a lot of things and hence the ~~SR will always be based on economics and real costs etc.
That said in South Africa we wouldn't expect to see a coal mine operate above a SR of 7BCM to 1tcoal. Hardrock would be in the region of 12t:1t but when Platinum was booming we say SR as high as 20:1.
Just a comment to add to the discussion
There cannot be a specific average stripping ratio of open pit mines around the world, simply because of varied ore characteristics and environmental conditions; as such this value can only be site-specific.
Based on the site-specific parameters defined, standard statistical models can be simulated based on large data sets. The size of data population can help improve the statistically accuracy of the specific environmental conditions. Key among these conditions are deposit geometry, hydrology, topography, provenance and age of deposit, among other factors. These factors are vividly discussed in: Griffith SV (1960) Alluvial Prospecting and Mining: Second Revised Edition: Pergamon Press New York Oxford London Paris: pp. 253
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