sharing in governance of extractive industries
Would this be a generalized comparison, or a case study comparison looking at same mineral being mined at a similar magnitude in both open pit and underground mining.
Generally, open pits are cheaper and quicker to develop, highly flexible with regards to the choice of mining faces hence tend to be more profitable in the face of fluctuating mineral prices or mining costs but are much more expensive to rehabilitate. Underground mines take longer and more capital to develop and offer little flexibility in the choice of faces but often times involve the mining of much higher grades hence can be much more profitable.
The companies or industry publications would have this. Maybe the mining schools (such as Colorado or South Africa etc), or the ICMM could guide you. Some of the information will not be included since underground mining also has external issues of labor, health and danger which companies and governments have become increasingly leery of.
I dwell on the category and haven’t come across one which compared costs, efficiency, profitability, trends etc with consideration of the important mine variables that could determine (angle of dip, ore-body thickness, ore-body hardness, host rock hardness, ore-body length, ore-body width; shortest distance from surface to ore-body, geometry of ore-body; magnitude of environmental impact, etc.
I belief global mining has generated a lot of variable costs, profits, trend, etc in respect of open pits and underground mines in variable combinations of the determinant mine variables which could be mobilized to enable statistical analysis to be carried out for the generation of empirical models which correlate. These models would help to compare open pit and underground mine in different combinations of the determinant mine characteristics accordingly.
Ambitious mining engineering student (s) could pick on the development of these empirical and a mathematical model for the selection of open pit or underground method in given combination of determinant mine charactecteristics, in accordance to obtained empirical to qualify for a mining engineering PhD.
I also don’t think it would be easy to mobilize data on mine profits, and therefore further suggest that for enabling the quantitative choice of mine method (open pit or underground), the empirical of overall unit mine cost ($/T) fit on the determinant s (mine and country variables) would fulfill. Country variables are those affecting on the overall mine cost (weather, fiscal regimes, infrastructure (power supply, transport, etc)) which vary from country to country and with time. Mine variables include the mining method (open pit and underground). Empirical will be more accurate if developed specifically for let’s say North America, South America, Russia, China, Australia, Africa south of the Sahara (less South Africa), that is, specifically for large Regions containing mining districts in similar country characteristics. Main challenge would be mobilization of the data, achievable if the international mining companies would cooperate.
For the traitement and processing the ore it's the same from open to underground. The difference it's in the extrating cost. Both use explosive, trucks and a lot of similar cost but underground have to manage ventilation (can represent up to 50% of total electricity cost , piping (to bring compressed air, water) , pump to dewatering) conveyor, shaft (used to move people and Ore), and light. Generally we see the the total cost of underground double on open pit.
Open bit could also be a lot more expensive than underground mining method if take into consideration parameters such as location of ore body relative to the surface, the thickness of ore-body and its angle of dip plus competence of host-rocks. Underground method is definitely cheaper than open pit for a massive ore-body which is located deep below the earth surface (let's say 500 m or deeper), especially when it is under the cover of competent rock which is also costly to excavate. Underground method is also cheaper than open pit for a thin ore-body (let's say thickness less than one meter) which dips vertically in competent host rocks. Underground method is also cheaper than open pit for a massive ore body which will require demolition of costly infrastructure on the surface to pave way for open pit mining. It means that a lot of conflicting factors influence on the overall costs for underground and open pit methods and therefore the need to develop a mathematical tool for the analysis and selection of the most cost effective from the two mining methods in variable conditions like geological and surface. Such tool also helps to establish when to change from open pit to underground method in the optimization of mining cost.