Search

In this paper, problem of short-term production planning for dimension stone quarries was mathematically modeled using a binary integer programming. The model includes an objective function, which was founded as the minimization of the costs due to the total cutting planes of the blocks. This objective may cause to maximization of the net present value (NPV) in dimension stone quarries. During the mathematical modeling the essential constraints are dimension stone quarry capacities and the market demand, block accessibility for the equipment and the reserve constraints. As a base, an optimal size and shape of extractable blocks should be first assigned according to the available extraction technique and the market demand, in order to create a geological block model. Then an economical block model is provided by assignment of a value of "one" for ore blocks and "zero2 for waste. Maximum profitability and minimum amount of the ore wastage can be gained using this plan and modeling.

Shallow ore deposits are mined by surface methods but a depth is reached in the case of most deposits after which underground methods are applied for the extraction of the remaining ore. The determination of this depth and its analysis is the subject of this paper. In order to determine transition depth from open-pit to underground mining on the basis of the allowable and economically feasible overall stripping ratios, an economic-mathematical equation is first introduced. Using the achieved equation and an analytical procedure on a particular two-dimensional hypothetical tabulate deposit, an effective formula is then established. The formula introduced here, together with the procedure adopted, could be used in all similar mining situations by the mining design engineer.

It is considered that the most economical method for the exploitation of Gol-e-Gohar Area 3 iron ore mine is to combine open-pit and underground methods. In this regard, the most critical problem is the determination of optimal final pit depth. In this paper, a method which was recently introduced on the basis of economical block models of open-pit and underground is used to determine optimal final open-pit depth of Gol-e-Gohar Area 3 mine with due regards to the future underground mining option. Considering a low cost and productive underground method as a feasible alternative for extraction of the lower part of this deposit, room and pillar was selected. It is concluded that after the assessment and comparison of different values for depth, optimal final open-pit depth was determined to be equal to 285 m.

In this paper, a relationship between dependant parameters and the crown pillar thickness is first introduced. This relationship defines geotechnical problems caused by thin pillars and economic considerations created by pillars that are thicker than the optimum size. For this purpose, a dimensional analysis as an effective physico-mathematical tool was used. This technique restructures the original dimensional variables of a problem into a set of dimensionless products using the constraints imposed upon them by their dimensions. A model is hence introduced that calculates the optimum pillar thickness. The relationship introduced here and the method applied can be used by mining engineers in all situations where a combined open-pit and block caving method is deemed to be the most appropriate mining method.

There are occasionally deposits with a potential of exploiting by a combined mining of open pit and underground. Hence, the most significant query emerges: where is the optimal transition depth from open pit to underground? In this study, in order to profitably select a single or combined mining of open pit and underground, as well as to determine optimal transition depth a methodology is presented. The model is established upon the economical block models of open pit and underground methods together with the Net Present Value (NPV)s gained by their mining. Main process in the model is economical comparison among several options of single and combined mining. To evaluate the model in detail, a hypothetical case is used. In this regard, among the all options a combined was selected that implying a height of 62.5 m as the optimal transition depth and the amount of 25.54 units of currency as the maximum total NPV achieved by the option.

During this paper, in order to identify the priority of consideration between the problems of “mining method selection” and “determining transition depth from open-pit to underground mining” an accurate procedure is introduced step by step. First, it is essential to specify if an ore deposit that potentially will have mined by a combined method of open-pit and underground mining. In this case, optimal final open-pit limit and depth must be initially determined. After that, if the rest of deposit below open-pit limit is economically considerable, it is necessary to select the most adequate underground method with emphasis on the high production rate and low cost methods. Then, it is necessary to determine optimal transition depth from open-pit to underground mining considering a crown pillar immediately below open-pit mining. Finally, the procedure with its algorithm was used for an iron ore deposit with the combined mining potential.