نشریه مهندسی منابع معدنی
سال دوم شماره 1 (بهار 1396)

The aim of stope limit optimization is to define an area with maximum economic value, for which, in accordance to the mining method used, all technical and geometrical constraints is considered. Although more than four decades have passed since the first presentation of underground stope optimizatiom algorithm, the development of these algorithms in comparison with similar algorithms used in open pit mines, have been very slow. This may be due to the high variety of underground mining methods and complexity of economic modeling of mining limit. In this paper a 3D comprehensive algorithm, which is called MLOA, is proposed. This algorithm runs on a variable value block models and is able to determine the number, height and optimal layout of levels. To determine the optimum limit of stopes, MLOA has used a heuristic algorithm which is called SOA. In SOA algorithm, Technical and geometrical constraints such as the minimum and maximum of stope dimension and minimum width of rib pillars have been regarded. The optimum location and dimension of stopes within specific level can be determined by using SOA. In order to verify the methods , the results of the application of SOA algorithm on hypothetical economic block model, are compared to similar rigorous algorithm’s results. The results demonstrate the capability of SOA algorithm in determining optimum limit of stopes.

There are various failure criteria for true triaxial stresses, which have initially been developed for the fracture of solid material such as metals. These criteria are applied for the stability analysis of wellbores and some storage caverns in rock media. In this research, true triaxial failure criteria has been investigated comprehensively by a new method using 12 groups of true triaxial strength test results of rocks including granite, monzonite, amphibolite, andesite, dolomite, Limestone, trachyte, marble, sandstone and shale. The Von Mises and Murrell criteria would not fit the test results due to their particular forms. Neither, Drucker and Prager criterion would fit the test results because of non-correlation between its defined parameters and the mechanical properties such as internal friction angle (ϕ). The relationship between octahedral shear stress (toct) and octahedral normal stress (σoct) having a constant exponent is shown to fit well the various groups of test results. The coefficient of this new criterion (B) that has been obtained by functional fitting is in good correlation with the parameters of ϕ, mi and σci. The power function relationship between toct and the mean of minimum and maximum principal stresses (σm,2) is found to be have a constant exponent also showing a good correlation with the various test results. The coefficient of this criterion (B') showed a good correlation with the parameters of ϕ, mi and σci., too. The linear relationship between toct and σoct of true triaxial strength test results was analyzed. A linear failure criterion was obtained to fit the 12 groups of results, as acceptable correlations have been obtained between the constant and coefficient of this new criterion with the mechanical properties such as internal friction angle (ϕ) and cohesive strength (C). Mogi-Coulomb linear criterion (relationship between toct and σm,2) also fitted the results and an acceptable correlation has been obtained between the defined constant and coefficient parameters of this criterion with the mechanical properties. The linear failure criteria are preferred that is because of having the constant parameter which is a function of mechanical properties of internal friction angle (ϕ) and cohesive strength (C).

Geophysical survey is one of the most important steps of exploration that must be conducted before exploration drilling ; Geophysical methods are different based on the physical properties of minerals and geological conditions. This study reports on Korkora, a section of Shahrak Iron mine located in the North East of Kurdistan Province and 60 km East of Takab. The geophysical study in the form of magnetic method was carried out in this area to investigate the mineralization. The total magnetic field intensity map was prepared after making the necessary corrections on the collected data. Having calculated the background magnetic field intensity and applying it to the raw data, the residual magnetic field map was drawn. Then, the vertical second derivative, upward to different heights, reduction to pole and analytical signal filters are performed on the data and the results were plotted and discussed on various maps. Then by designing a number of profiles on anomalies, inverse modeling by mag2dc software is done on these profiles. Euler method was used to determine the depth and shape ratio of deposit formation. Finally, by combining all the information obtained and by filtering the data, a number of points were proposed as prospectus points for exploration drilling. The drilling locations were selected so that they would satisfy the maximum chance of being within the ore body deposit.

The study on the quality of groundwater is important for drinking, industry and agriculture purposes. In this research, the hydrochemical data collected from exploitation wells in Gonabad basin- Khorasan Razavi, have been studied in period of 5 years (from 85 to 90). Graphical methods and classification of underground water quality show that the type of water is mainly that of sodium sulfate. Spatial distribution of water quality using multivariate statistical R-mode model states that water quality in this basin is affected by two factors. The first factor which is known as salinity and water hardness in plain is the linear combination of Ca2, Mg2, Na, SO42-, Cl-, TH and EC. The second factor is the combination of HCO3-, CO32- and pH which indicates water alkalinity for which higher pH is an evidence. Further in the research, the modeling of quality parameters TDS, EC and TH is done with chemical parameters such as primary ions and pH using artificial neural network. The comparison of results obtained from filed with those of neural network is very analogous showing the high ability of this method for water quality prediction. Therefore, in case of lack of data in the area, this model can be used to predict water quality in target locations. The results can be used to environmental management and better exploitation of groundwater resources.

It is well documented that in gas treatment units in addition to H2S absorption, a large percentage of CO2 is absorbed to solvent. CO2 absorption in gas treatment units causes loss of energy and a reduction in the capacity of sulfur recycling unit. According to the fact that higher amont of CO2 exists in Sarakhs gas region and also that loss of chemical solvent (Amine) is higher in a unit with higher CO2 content, this research deals with CO2 absorption performance with physical and chemical solvent mixture ,Sulfinol-M. The results indicates an overall flow rate reduction of MDEA solvent from 400-480 m3/hr for 40-50 %wt MDEA to 315-420 m3/hr with the relative compound of H2O 20-40 %wt, Sulfolane 40-50 %wt , MDEA 20-40 %Wt for Sulfinol-M solvent mixture. Also Co2 absorption by this solvent will be 0,001555 moles less than MDEA solvent. Therefore with relative change in water level, Sulfolane and MDEA we can control and optimize the regenerative energy required to achieve required market characteristic, investment cost, the increase of Sulfur recovery unit capacity and the decrease of solvent flow equipment.

Dimensional stone mining includes tedious activities. It is necessary to study the safety and risk analysis with respect to the large volume of the diamond wire saws used and the number of accidents occurs in quarries. In this study, a safety risk analysis is done for Badeki marble quarries using FMEA method identifying the accidents happened in the mines. The results of analysis and ranking the risk of accidents showed that, wire saw tearing and rock fall are the biggest thread in these quarries. The average safety risk before and after reducer action in the quarries studied are 17.33% and 5.33%, respectively. It indicates a 69.23% decreasing trend in the total risk in these quarries. The results of this study showed that the initial risk in these mines can be greatly reduced by doing some changes and some preventive notices to secure the equipment and personnel.

Designing flotation circuits is very important in terms of number of cells, in series or parallel topology to achieve the maximum efficiency. In most factories, the conventional forms of design are used. In this article, plug flow is used for number of cells calculation and estimating and designing the recovery of the ropher circuit. The model replicates Nochon complex flotation circuits, for which a sample of the mineral copper was collected and tested. The two key parameters of kinetic study k & R, are obtained with flotation parameter (k=0.13; R=96.88; RTD=28 min). The retention time was also calculated to be 28 minutes. Using the aformentioned Plug flow model and taking the factory production capacity into account the flotation circuit was determined with up to 3 parallel line and 7 series of cells. In other words from 21 cells with 4 minutes residence time, volume and total recovery are obtained 4 m3 & 94.34%. These results correspond with the results of a laboratory cell with 28 minutes Retention time and Plug flow.