فصلنامه مهندسی معدن
پیاپی 48 (پاییز 1399)

This study was carried out to obtain the optimal mechanism and conditions for the separation of fine particles (-38 µ) of quartz (float) from hematite (depression) by direct carrier flotation. In this study, first, the type and size of carrier particles were determined to adsorb pure quartz particles on the surfaces of these particles. Then, the effect of various factors such as the type and concentration of collector and pH on floating particulate matter on the carrier particles was investigated using several experiments. In order to select carrier particle, the effect of pyrite and calcite on the selective collection of quartz particles was tested. According to the results of experiments, calcite particles in the size of (+75 –106) micron were selected as suitable carriers for the adsorption and collection of fine quartz particles and then their floating. It was also found that the preparation of calcite particles with the collector, before adding them, had a positive effect on the adsorption of fine quartz particles. Experiments showed that the best conditions for calcite particles to float at pH = 11.5 with presence of dodecyl amine collector at a concentration of 1.5 kg / ton. After investigating the effect of process variables on the responses obtained, optimization of the operating the aim was to maximize grade and recover quartz in the flotation float concentrate. In the optimum condition, carrier size (+75 -106) micron and amount of 34% quartz was obtained. The optimum results showed that the quartz recovery in the concentrate was about 71% and its grade about 81% of a synthetic feed with a ratio of 40% hematite and 60% quartz.

The study area is the Yeganlly and Qinranjeh area, southwest of Zarshuran gold mine, 35 km away from Takab city, West Azarbaijan province. The study area is located on the southwest edge of the mine. Only 17 borehole data were available for this study and were evaluated. Geophysical data includes 17 parallel profiles with a length of about 735 meters with a 30 meter distance electrode and a polar-bipolar mapping array according to the topography of the area. The objective of introducing and presenting a method for simulation and single-multivariate estimation using the most widely used methods, such as usual cracking, ordinary cokriging, sequential simulation, sequential coexistence simulation, in order to reproduce more precisely the initial region variables and Secondary will be. Geophysical data was constructed of a so-called sulfide factor. After normalizing, for each variable, the variography chart was drawn and estimated using the Kriging method according to the variogram in the borehole coordinates. Then, by normalizing the data in the specimen, analysis of the main components on the variables was performed using SPSS software. The output of this part was two factors that the fact that the amount of gold mineralization was high was introduced as a mineralization factor. Now, with two existing factors, namely, the sulfide factor (geophysical factor) and the gold mineralization factor in the studied area, the combined interactions between the built-in block models were combined with the estimation and simulation; ultimately, validation was also performed by evaluating and estimating two boreholes Isolated randomly using other specimens at the end. It was found that according to the evaluated results, when estimating the gold grade when using sulfide factors and mineralization in coking, the gold monorangle estimation by conventional Kriging estimation is closer to the real values of gold.

The main objective of this research is to present a stable and optimal design of the ultimate slope of the eastern wall of Shadan Gold-Copper open pit mine based on the calculation of minimum factor of safety (1.20) by numerical modeling method under different conditions of slope geometry. Numerical modeling was performed using finite difference method (FDM) and FLAC3D software which is capable of calculating the factor of safety (FOS) by shear strength reduction method. Therefore, a set of 3D numerical models in different scenarios were investigated by varying the geometrical properties of the pit slope (width, height and face angle of bench, pit depth and overall slope angle). Based on the analysis carried out during the different scenarios, finally the fifth scenario with minimum safety factor of 1.20 was introduced as the proposed pattern. According to the initial design (first scenario) with a safety factor of 1.39, in the fifth scenario by decreasing the benches width from 6.8 m to 5 m and increasing their height from 10 m to 12 m which increases the slope angle of the bench face (from 70 degrees to 73 degrees) and overall slope angle (from 43 degrees to 52 degrees), safety factor of the ultimate slope was reduced to a minimum of 1.20. The maximum impact of the change in the safety factor is related to shear strain and horizontal displacement in the model such that the maximum shear strain (1.12 e-2 m) and the maximum horizontal displacement (-25.75 cm) are related to the fifth scenario with minimum safety factor (1.20). Whereas, the maximum vertical displacement (29.63 cm) is related to the first scenario model (FOS = 1.39) with the maximum slope height (pit height) of about 219 m, which shows the least influence on the value of the safety factor.

In deriving the convergence –confinement method curves for a tunnel, convergences of side wall, roof and floor may be different, because of the weight of the failed or plastic rock mass. In this paper, a semi-analytical method of the ground response curve and the lining characteristic curve for a tunnel excavated in an elastoplastic strain-softening rock mass, considering axial-symmetric condition, is proposed to study the effects of the weight of the plastic or failed region developed around tunnels. In the proposed method, Mohr–Coulomb yield criterion and plastic potential function are used for the ground medium. The gravity loading is considered as a radial body force being applied to the ground medium which is not the same for different directions. Two flexible and inflexible lining theories are presented for considering the concrete lining stiffness. In flexible lining theory, the influence of the lining is considered as a uniform internal pressure; while, inflexible lining theory, the lining is taken as a thick-walled cylinder. By combining these two theories the concrete lining stiffness can be modelled. The derived differential equations cannot be integrated analytically; thus, they are solved by invoking finite difference approximations. Several illustrative examples are given to demonstrate the performance of the proposed method and to examine the effects of the gravity loads. The results obtained by the proposed method show that the gravity loads may affect the tunnel convergence, especially when the plastic zone is wide.

Using the Cement Paste Backfill (CPB) is developing in the underground excavations. In this study, the potential of tailings in the preparation of CPB and the effective factors on its strength and slump were studied using the design of laboratory results. The studid CPB is consisted of the tailings of the Lead and Zinc Anguran mine. Heavy media waste (Hmw) as a coarse mass, leach tailing (Lt) as a fine aggregate and Portland cement type 1 as a binder were used to make the CPB. In order to minimize the number of experiments and provide an appropriate combine, the design of the experiments was carried out based on the Response Surface Method (RSM). The results of the design and laboratory tests showed that the increase of the Lt/Hmw ratio is more effective than the other components on the CPB’s compressive strength and slump. Increasing the Lt/Hmw, significantly increases the compressive strength and decreases the slump. Also, with increasing the Lt/Hmw, the peak strength recorded in stress-strain graph is increased, which is, less effective at higher values. As the ratio increases, the wave velocity increases, also. Hmw has a positive effect on paste slump, but decreases compressive strength. The increase of 13% of the Hmw reduces the compressive strength by 2.7 times and increases the slump by more than 4 times. Increasing the cement amount increases the compressive strength of the samples, but its effect is less than the Lt/Hmw. Water reduction has been accompanied by a reduction in the water-to-cement ratio, which accelerates the curing of the samples and increases the compressive strength of the CPB samples. In order to optimize the process, according to the compressive strength and target slump, the values 3.72 and 27.89 percent and the ratio of 0.82 for cement, water and Lt/Hmw, respectively are suggested.