The determination of underground and open pit mine limit using investment theories

In our day, the increasing production costs and competitive environment seen in mining sector require the evaluation of underground resources in the most efficient and economical way and also entail an increase in production. It is well known that mining investments consist of long-term and highly hazardous operations which should be planned beforehand. Thereby, the design and planning of open pit and underground mines at optimal mine life and production capacity is very important.The solution to existing mining problems relies upon a proper mine layout and the escalation of profitability. In open pit and underground planning, the haulage costs naturally increase with the increasing depth of the mine. In addition, the prediction of overall operating costs and unit ore production cost by taking into consideration the factors such as the geomechanical parameters of the rock that are directly effective on production cost, and also the excavation difficulties, slope stability and work safety plays an important role at the feasibility. In this kind of feasibility studies, the revenues, which will be gained during the life of a mine, is evaluated by means of Net Present Value (NPV). According to this method, the most ideal mine life and capacity that maximizes the NPV determines the mine limits and depth.Since the mine sites comprise a unique dynamic and variable structure depending on the geologic and geopgraphic conditions. Thefefore, the planning stage gets harder and more complicated. Therefore, every mine site should achieve a scientific-based mine planning that is convenient for its own specific circumstances. As a result of these conducted studies, sometimes the mentioned mine site is planned entirely either in the form of an open pit or underground mine. The essence of this planning, particularly after a certain period of time and depth, a combined production method which facilitates a transition between open pit and underground mining methodsKeywords: Open pit, Mine planning, Net present value, Optimum capacity, Economical mine life