نشریه مهندسی منابع معدنی
سال سوم شماره 1 (بهار 1397)

A geochemical evidence map is one of the most important informative layers in minerals potential mapping. In this research, In order to overcome the disadvantages of discrete evidence maps, we used the continuous fuzzy method to produce geochemical evidence maps. The Varzaghan 1:100,000 sheet map that is located in arasbaran metallogenic belt and hosted the Sungun porphyry-skarn copper deposit was studied. In this study, we have used 1067 stream sediment samples as primary data that was studied by Geological Survey of Iran. At first, the catchment basins for each sample have been drawn and the signature of samples have been allocated to corresponding basins. In addition, the signature elements of porphyry copper deposits like Cu, Mo, Ag, Au, As, Pb and Zn have been used to detecting the potential mineralized areas in the region. In the interest of fuzzifying the maps of each signature elements that mentioned, Large and logistic fuzzy functions have been used. Following to fuzzifying, the geometric average method has been applied and then prediction-area plots was used to validate the results. It has been shown that fuzzification by Large function is better as it can predict the 80 percent of mineral occurrences by utilizing 20 percent of the study area

Due to the increasing demand for more production rates and output from oil reservoirs, the re-activation of oil wells in Iran is a vital task. Oil production reduces overtime because of a decrease in reservoir's pressure and also as a results of the closure of cracks and microscopic holes. Hydraulic fracture, as a method for stimulating oil reservoirs related to various factors, including characteristics of the environment in which the fracture grows. Mechanical properties of layers has been recognized as one of the most effective parameters on the progress of hydraulic fracture and its geometry. In this study, the primary rock was considered as non-cracked. In this research, numerical modeling was done by ABAQUS software in 21 different cases for which the effect of each input parameters on the hydraulic fracture pressure was investigated by performing sensitivity analysis. The input parameters were well's data and included Young's modulus, minimum and maximum horizontal stress, vertical stress, tensile strength, Poisson''s ratio and pore pressure. The required data is obtained from the excavated wells in carbonate rocks in Iran. The results showed minimum horizontal stress has the highest impact on the hydraulic fracture pressure. Finally, using SPSS software and by performing multivariate regression analysis, a formula was made using the numerical modeling data to estimate the hydraulic fracture pressure. The results of statistical analysis corroborate the precision of regression line and consequently the suggested formula. In this formula, the parameters such as minimum horizontal stress, the difference between minimum and maximum horizontal stresses, pore pressure and tensile strength, have the most effect on the hydraulic fracture pressure respectively. Using the presented formula in this study, the hydraulic fracture pressure in carbonate wells with different properties could be obtained. Gaining this pressure will help to determine the proper pump and case to reduce operating costs.

Basically, in the chain of the decorative stone industry, the cost of transporting the excavated rock from mine to the rock cutting factories, and then shipping of the processed plate and slab stone to the market places has a major impact on the finished product price. In this research, firstly, each of the decorative stone chain components including mines, rock cutting factories and consumer markets in Iran was divided into 10 main poles. Then, the linear programming model for minimization of total transporting tonnage and distances of raw rock from poles to processing poles and processed slab from mine to trade materials and transferring processed rocks from factories to market poles were defined. The constraints of the model were defined based on the proportion of production capacities in poles throughout the production chain. After solving the model with the GAMS software, the optimal delivery tonnage between the poles as scenario 1 was calculated. Also, two separate scenarios have been defined in terms of 20 percent increase in production capacity of mine poles and 20 percent increase in consumption and processing capacity poles. The second scenario reduces the average shipments per unit product by 3.9 %, but it has no positive impact on the utilization ratio of the production capacity in mine and factory poles. The third scenario improves the utilization rate of the mines poles, however increases the total shipment of the raw material from the mine to the factory by 28%, and also increases the average distance per unit product along the chain by 8.2%. This scenario could lead to increasing the unit production cost and reducing the competitiveness of the final product.

In order to achieve maximum recovery and minimum absorption level of radiation in underground uranium mines specific measures must be taken. One way to achieve this goal is to employ the backfilling method using hydraulic concrete fills, in particular in the tunnel cut and fill method. The backfill is a material which is used to fill the excavated underground stopes to provide support and safety for the mining operations. In this research various mixes of hydraulic concrete fillers were prepared at the laboratory scale. The underground mine waste rock, open pit waste rock, natural river sand, and barite sand were used as backfilling main ingredients and representative samples of each mix design were prepared for the laboratory tests. Moreover, large scale samples of concrete hydraulic fills were cast at varying thicknesses in in the vicinity of uranium ore to enable examining the radiation level. The test results demonstrate that the use of hydraulic concrete fills can provide safety and stability to mining activities.

It is now generally accepted that froth appearance is a good indicative of the flotation operation conditions. Image analysis technology now offers a viable means of monitoring and control of the flotation process. In this paper, the relationship between the operational variables (i.e. gas flow rate, froth depth, slurry solids%, frother/collector dosage and pH) and the froth features (i.e. bubble size, froth velocity, froth colour and froth stability) in the column flotation was discussed during desulfurization of an iron ore using response surface methodology.Image analysis techniques have been developed and used successfully to characterize froth. Results of the CCD experiments showed that the flotation variables have different effects on the froth features. The effect of pH and the interaction of the effect of the pH and collector dosage have a significant impact on all mentioned froth features. The results show that the process state can be accurately deduced from the froth surface appearance, providing a convenient way to quantify changes in parameters as a function of the process control.