نشریه مهندسی منابع معدنی
سال نهم شماره 2 (Summer 2023)

The pore geometry and topology properties of rocks are significant for a better understanding of the complex hydrologic and elastic properties. If the complexity of porous media is considered, reliable results can achieve. In three-dimensional imaging of cavities, these complexities are taken into account. In this study, by conducting different methods deep understanding from some sandstones pore space is undertaken. Three series of 2D micro-computed tomography sandstones binary images have been considered, each of them imagined as a 3D binary image. Using novel skeletonization and pore-throat partitioning algorithms some network properties have been evaluated and compared for three cases. Those properties are pore and grain size distribution, throat length frequency, and coordination number frequency. Also, geometric measures in 2D and 3D have been considered using Minkowski functionals. The area, the perimeter and the 2D Euler number of 2D binary images and the volume, the surface area, the mean breadth also known as integral of the mean curvature, and the 3D Euler Number of 3D binary images are considered.

In deep mines with combined mining potential, optimization hauling systems as the technological phase with the largest share in the total operation costs are essential from the aspect of achieving the profitability of the mining project. In this study, using a hybrid semi-quantitative approach, the impacts of haulage systems in large-scale and deep open-pit mines with combined mining potential were evaluated on mining options. According to the results of evaluating the use of the haulage system in the Sungun copper mine, the most appropriate haulage system was selected in-pit crushing and conveying system, truck-shovel, battery trolley, and trolley assist, respectively. Also, the use of the modern haulage system in the Sungun copper mine had a direct impact on the following mining options, respectively, with the intensity of -11.03, 32.94, 11.73, 17.06, and 15.07. (a) independent underground mining, (b) independentopen-pit mining, (c) simultaneous mining, (d) sequential mining, and (e) combinations of simultaneous and sequential. The obtained results indicate that the use of a modern and suitable haulage system for the mine leads to the desire to continue mining with the open-pit method, which leads to an increase in OTD.

As near-surface mineral resources are being depleted, mining operations are focused on deepening. Rising environmental concerns prefer underground mining methods because their footprint is less than that of surface mining methods. Among the underground mining methods, block caving is a method with low operating costs and comparable production rate to open-pit mines. Mine design and planning optimization is performed to ensure the optimal use of mineral resources with minimal possible extraction costs. Stope boundary optimization is vital in the underground mining planning process, and numerous algorithms have been proposed in that regard. The floating stope algorithm is the most widely used algorithm which is presented for those mining methods where selective mining is possible. This paper tries to apply the floating stope algorithm for stope boundary optimization in the case of block caving. In that regard, a framework is discussed to determine the input parameters of the floating stope algorithm that are suited for block caving including minimum block size, floating ranges, and cutoff grade. These parameters are defined to customize the floating stope algorithm for the block caving method. Then the customized algorithm is applied to optimize the boundary of the underground block caving stope. Then, the corresponding undercut level is determined using the “effective cross-section” heuristic. The procedure is applied in the Songun copper mine. Based on the results, the minable reserve is 617 million tons with an average copper grade of 0.53%.

The abrasivity of materials is of vital importance in selecting an affordable excavation method in the early stages of a tunneling project. The amount of specific energy and the Mode I and Mode II stress intensity factors in the eroded disc is more than the non-eroded disc. Vickers hardness number rock (VHNR), rock abrasivity index (RAI), Cerchar abrasivity index (CAI), LCPC abrasivity coefficient, and Norwegian University of Science and Technology (NTNU) abrasion test are among the methods for estimating rock abrasivity. Correlations were proposed in this study for estimating the CAI of sandstone and tuff. To achieve reliable comprehensive results, various kinds of sandstone and tuff with different geological properties were selected. Sandstone and tuff samples were collected from different regions. Various tests were then carried out on prepared rock specimens to determine the uniaxial compressive strength (UCS), tensile strength, longitudinal waves velocity, Schmidt hammer rebound hardness, and the equivalent quartz content (EQC). Two correlations were presented by analyzing the experimental results with the help of SPSS and Excel. The first correlation estimated the CAI of sandstone based on the UCS and EQC with a coefficient of determination (R2) of 0.81. Moreover, using data analysis in Excel, another correlation was proposed to estimate the CAI of tuff. The second correlation estimated the Schmidt hammer rebound hardness of tuff with an R2 of 0.88.

Although the flotation separation of sulfides and their electrochemical interactions have been examined in some investigations, study the direct relationship between the flotation kinetics of sulfides and their galvanic interactions during the process yet has not been addressed. To fill this gap, an extensive study was conducted to explore the effect of galvanic interactions for chalcopyrite and pyrite on their flotation kinetics when they are wetting ground by three different grinding media types (steel, chromium, and ceramic). Assessment of the flotation test results indicated that there was no galvanic interaction between the ceramic grinding balls and chalcopyrite. The galvanic interactions were mostly related to the grinding of chalcopyrite by steel balls. EDTA analysis showed that by increasing the amount of iron oxy/hydroxy and their precipitations on the surface of chalcopyrite, the recovery of chalcopyrite was decreased. Furthermore, increasing the pyrite content in the flotation of chalcopyrite increased the flotation rate constant and then decreased it. Flotation tests demonstrated that grinding chalcopyrite by ceramic media type, which has lower electrochemical activity in comparison with the other considered media, can be resulted in a higher flotation rate constant and ultimate recovery. Grinding the mixture of chalcopyrite and pyrite by steel or chromium media can show almost the same effect on the flotation rate constant and ultimate recovery. In general, the experimental results showed that by increasing the galvanic interaction, the flotation recovery and flotation kinetics were decreased.

One of the inseparable components of the grinding process in tumbling mills is the grinding media used in them. Despite the simplicity of grinding media shapes in a tumbling mill, their effect on breakage performance as well as on the mill power draw has remained a complex problem. A large share of energy consumption in mineral processing plants is related to grinding operations, so the study of power consumption in this sector is very important. This study compares the effects of conventional rods (simple rods) and grooved rods on the mill power draw in a dry rod mill at various mill speeds and grinding media filling. The results of the study showed that with an increase in grinding media weight and mill speed, power consumption was increased for both types of grinding media studied. The specific power rate decreased with increasing the speed and media filling. By increasing mill speed, the sensitivity of the specific power draw to the grinding media filling was increased. The specific power draw of grooved rods at low and medium speeds was shown to be more than that of simple rods, but at speeds above 60% of the critical speed, the specific power draw of the grooved rods was lower than that of the simple rods. Using an empirical model, the experimental and model values were compared. The results showed that the prediction of the mill power draw using the presented empirical model, in the range of low and medium speeds is more reliable. Therefore, using this model at low speeds is perfectly valid. However, as speed increases, its credibility decreases.