International Journal of Mining and Geo-Engineering
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University of Tehran,正常發行
選擇卷期
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In this research, the dissolution of chalcopyrite was investigated under atmospheric pressure, with a sulfate medium at low temperatures, in 30°C to 50°C. In the galvanic interaction between chalcopyrite and pyrite, pyrite is used as a leaching catalyst. Effects of different parameters such as temperature, stirring speed, pyrite to chalcopyrite ratio, particle size, and solution potential were examined. Results showed that maximum copper recovery in low temperature was achieved after 24 hours, under the following condition: stirring speed of 800rpm, pyrite to chalcopyrite ratio of 4, solution potential of 440mV, temperature of 50°C, and particle size of -38 microns. In addition, kinetic studies indicated that chalcopyrite dissolution with pyrite followed the shrinking core model, and the reaction was controlled by the surface reaction. Activation energy (Ea) was calculated as 88 kJ/mol.
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In the present study, an investigation was carried out on Parvadeh coal mine in Tabas, Iran, to survey the effect of fractures on unusual methane gas emission in coal mines. This coal mine was chosen to be investigated because of its high methane gas content in the coal body and available data from sensors in desired locations. Gas concentration monitoring programs were carried out at the mine site and a large amount of data were collected and analyzed. It is revealed that there is a good correlation between excavating the fracture-bearing faces and high methane gas emission events at the mine site. High gas emissions have been observed before, during, or after excavating the fracturebearing faces. When gas content is high and all boundary conditions are met, rockbursts, faults movement and also mining activities can trigger unusual gas emission, and sometimes the gas gushes are violent enough to fit into the category of gas outbursts. Since the fracture generation is happening before the increase of gas concentration in the air, a sensitive and highly accurate microseismic monitoring system can be used to detect locations of rock fracturing, thus provide an effective means to issue warnings of high gas emission in the working area.
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In this research, the zinc extraction from a low grade zinc concentrate produced from the accumulated flotation tailings was investigated using the bioleaching process. Zinc content was initially upgraded to 11.97% through flotation process. Bioleaching experiments were designed and carried out by a mixed culture of Acidithiobacillus ferrooxidans, Acidithiobacillus thiooxidans, Leptospirilium ferrooxidans, as well as a mixed moderate thermophile bacteria in the shake flasks. The effect of two bacteria types, the indigenous bacteria accompanied by concentrate sample and added mixture of bacteria, were evaluated. The term of indigenous bacteria refers to the bacteria which initially exists in the natural concentrate sample. The results showed that more than 87% and 94% of Zn was dissolved in the bioleaching condition of mesophile and moderate thermophile bacteria, respectively. Comparing the bioleaching and leaching tests indicate that mesophile bacteria improves the Zn extraction by 36%, in which the contribution of concentrate indigenous bacteria (test condition of non-inoculation) and added mesophile mixed bacteria were equal to 34% and 66%, respectively. In addition, moderate thermophile bacteria improves the sphalerite leaching up to 38% in which contribution of the concentrate indigenous bacteria and added moderate thermophile bacteria were about 50% separately.
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Application of truncated gaussian simulation on ore-waste boundary modeling of Golgohar iron deposit
Truncated Gaussian Simulation (TGS) is a well-known method to generate realizations of the ore domains located in a spatial sequence. In geostatistical framework, the geological domains are normally utilized for stationary assumption. The ability to measure the uncertainty in the exact locations of the boundaries among different geological units is a common challenge for practitioners. As a simple and informative example of such a boundary, one can consider the boundary between ore and waste materials in an ore deposit. This boundary addresses the percentages of the ore and the waste and also affects the future economy of mine and all precedent mine designs and mine plans. Deterministic approaches, based on interpretation of geological phenomenon, provide just one scenario of ore-waste variation, and do not offer a model for uncertainty of boundaries. On the other hand, geostatistical simulations, based on stochastic models, can measure the uncertainty of such a boundary. Through different techniques for spatial simulation of the categorical data (geological domains), truncated gaussian simulation has been proved to be versatile when geological units have sequential geometries and/or there are few number of indicators (ore and waste). This study addresses the application of TGS for conditional simulation of ore and waste domains in Golgohar iron ore deposit. Separation of the ore and waste domains has affected the ore tonnage estimation and resource evaluation. Various simulations can be considered as the spatial realizations of ore and waste. TGS can generate realizations of the domains and measure the uncertainty of ore-waste boundary. The accuracy of results was checked through performance evaluation section and different scenarios (e.g. best, average and worst). The best scenario is the one with the most accuracy that is calculated from confusion matrix. The scenario No. 44 with 96 million cubic meters tonnage has an accuracy over 86 percent that is proposed as the best scenario for future planning and mine design.
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Tunneling through cities underlain by soft soil, is commonly associated with soil movement around the tunnels and subsequently surface settlement. The predication of ground movement during a tunnelling project and optimum support pressure could be based on analytical, empirical or the numerical methods. The commonly used Earth Pressure Balance (EPB) tunneling machines, make use of the excavated soil in a pressurized head chamber to exert a support pressure to the tunnel face during excavation. This face pressure is a critical paramater in EPB tunnelling because the varying pressure can lead to the total failure and collapse of the face. The objective of the present study was to evalute the critical supporting face pressure and grout pressure by observation of the vertical deformation and horizontal displacement of soil body during tunneling. The face pressure and grout pressures were varied to see how they might influence the magnitude of surface settlements/heave. A numerical model using PLAXIS-3D Tunnel software package was developed to analyze the soil movement around the tunnel which can involves different geotechnical conditions. The ground surrounding the tunnel was found to be very sensitive to the face pressure and grout pressure in terms of surface settlementand the possibility of collapse in the body of soil.
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Fractal and multifractal singularity are the techniques for detection of depletion and enrichment of elements in geochemical exploration. On the other hand, the index of vertical geochemical zonality (Vz) of Pb.Zn/Cu.Ag is a practical method for exploration of blind porphyry copper mineralization. In this study, these methods are combined for recognition, delineation, and enrichment of Vz in Jebal- Barez in southern Iran. The studied area is located in the Shar-E-Babak-Bam ore field in the southern part of the Central Iranian volcano–plutonic magmatic arc. The region has a semiarid climate, mountainous topography, and a poor vegetation cover. Seven hundred samples of stream sediments were taken from the region. Geochemical data subset represent a total drainage basin area. Samples were analyzed for Cu, Zn, Ag, Pb, Au, W, As, Hg, Ba, Bi by atomic absorption method. Prospectivity map for blind mineralization in this area was prepared. The results are in agreement with previous studies in the region. Kerver was detected as the main blind mineralization in Jebal- Barez which was previously intersected by drilled boreholes in the exploration process. In this research, it was demonstrated that employing the singularity method for zonality separation of geochemical anomalies, as opposed using the singularity of elements, improves prospectivity mapping.
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The microscopic and geomechanical properties of igneous building stones include the extent of alteration, presence of micro cracks, peak strength, porosity, proportion of detrimental minerals, etc. Porosity has reportedly a devastating impact on the peak strength of igneous rocks. The quartz diorite rock samples in this study were selected from five quarries in Natanz of Iran and were subjected to microscopic and geomechanical investigations. The extent of alteration and the detrimental minerals affecting the strength of the samples were identified from examination of thin sections. Therefore, the geomechanical tests on density, porosity, durability index, the Brazilian, and triaxial tests were conducted following the ISRM standards. The findings from microscopic studies revealed that compared to porosity, alteration has a more intense impact on rock’s peak strength. The results were compared to standard values and a qualitative correlation between strength and microscopic properties was detected revealing the importance of construction stones microscopic studies. The correlation thereupon may be adopted in the exploration, exploitation, and processing of construction stones to avoid heavy expenses and damages to the environment.
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In this research attempts were made to create a mortar with relatively high uniaxial compressive strength (UCS), easy casting, high flexibility, instant hardening, low cost and easy availability. The main use of this material is to physically model the mechanical behavior of jointed rocklike blocks. The effect of four parameters such as joint roughness coefficient (JRC), bridge length (L), bridge angle (γ) and joint inclination (θ) on UCS of non-persistent jointed blocks were studied. For this purpose, 35 cylindrical specimens with a broad range of plaster content (P) and cement content (C) in different ages were tested. In order to increase the strength of blocky specimens, some amounts of retardant and lubricant agents were used. The results demonstrated that the utilization of 3 wt.% (weight percent) lubricant MGAR106 and 0.05 wt.% retardant decreases water content by 12.5% and increases plaster and cement content by 8.3% and 4.17% respectively. Consequently, UCS of blocky specimens increased by 284.33%. In order to formulate the effect of P/C content and also the age of cylindrical specimens (A) on compressive strength (UCS), Multivariate Non-linear Regression (MNR) and Bayesian Regularized Artificial Neural Network (BRANN) models were employed. The results showed that BRANN approach is able to provide more precise predictions of the specimen UCS compared to the results from MNR model. Moreover, P/C content had more impact on UCS than the specimen age had. Finally the UCS tests on blocky specimens indicated that an increasing in JRC, bridge length or bridge angle results in a rise in UCS; moreover UCS would be in its minimum when joint inclination was 60°. Furthermore, the capability of produced material to model cracking behavior of jointed blocks was verified.
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In this research, first of all, the common problems in fragmentation analysis are reviewed with regard to the reliability and rapidity of the evaluation. Then, the available methods used for evaluation of blast results are described. The usual errors especially in recognizing rock fragments in computer-aided methods, and also, the importance of accurate determination of fragment sizes in image analysis methods are illustrated. After reviewing previous research work in this area, an algorithm is proposed for automated determination of rock particles’ boundary in Matlab software. This method can automatically determine the particles boundary in very short time. The results of proposed method are compared with those of Split Desktop and GoldSize software packages in two automated and manual states. Comparing the curves extracted from different methods reveals that the proposed approach is accurately applicable in measuring the size distribution of laboratory samples, while the manual determination of boundaries in conventional software packages is very laborious and time-consuming; and moreover the results of automated netting of fragments are very different from real values due to the error in separation of the objects.
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Reliable characterization of subsurface soil in urban areas is a major concern in geotechnical and geological engineering projects. In this regard, this research deals with development of a 3D geological engineering model for the subsurface soil of the city of Mashhad, Northeast Iran, using Sequential Gaussian Simulation (SGS) approach. Intense variability of soil in the study area has sometimes caused major problems in civil engineering projects of the city. Therefore, a better understanding of the soil-related problems is critical for current and future civil engineering work. The main objectives of this study were investigating the spatial variability of soil through variograms and then predicting the values of soil properties at un-sampled locations using SGS method. In this study, some geotechnical index parameters including percentage of fine-grained material, plasticity index, and liquid limit have been employed as input data. A database including the data of 1750 boreholes was built and the hard data were transformed into normal scores in order for them to be applicable as input data in SGS modeling. Maps related to the average of all realizations along with Coefficient of Variation (CV) were provided for each variable as well. Then the maps were interpreted according to the sedimentary environment of Mashhad.