فصلنامه مهندسی معدن
پیاپی 50 (بهار 1400)

With the increase in complexity of mineral deposits, understanding the grade variability is of high significance in getting enough information about the deposit, preventing financial losses and identifying optimized plans during and after exploitation. Likewise, mineralogical variability, grade, alteration, … can highly effect metal recovery. Modeling these parameters is seriously substantial in order to have an optimized exploitation of the mine and to minimize the risks and costs. This study used the dataset of 91 drill holes from Sari Gunay epithermal gold deposit located in north-west of Iran to model gold grade and the recovery resulted from leaching tests. Initially, the oxide and sulphide zones were distinguished using Indicator Kriging and Simulation. Then the gold grade and recovery in each zone were modeled with the application of sequential Gaussian simulation and the developed block model. The grade-recovery curve was then drawn to estimate the total tonnage amount of the deposit which was related to the sulphide zone in more than 70%. Then with the help of recovery simulation data, the grade×recovery was considered a preferable parameter in depicting the curve and estimating the reserve.

Concrete is now widely used in civil engineering industry. Concrete structures have shown weak performance against tensile and bending forces, unlike their high compressive strength. To improve their bending and tensile behaviour, they are enforced by different materials such as fibers. In this paper, the impact of volume ratio of two polymeric fibers, namely Korta Wave Blend (KWB) and Korta Blend (KB) manufactured by Sirjan-nano Company, was statistically investigated on the mechanical properties of fine-grained concrete. Samples having 0, 0.5, 1, 1.5 and 2% volume ratio of each polymeric fibers were prepared and uniaxial compression, indirect tensile (Brazilian) and triaxial compression tests were carried out. Mechanical properties of mixtures including uniaxial compressive strength (UCS), Elastic modulus, tensile strength and triaxial compressive strength at different confining pressures were measured for each volume ratio. Using the results of triaxial compression tests, the cohesion and friction angle were calculated for each volume ratio. Results of uniaxial compression tests showed that the KWB fiber has lower impact on the increase in the UCS compared to that of KB fiber. The impact of increase in the KWB volume ratio on the Elastic modulus was not statistically significant while the increase in the KB volume ratio up to one percent resulted in a statistically significant increase in the Elastic modulus. Results of indirect tensile tests showed that the presence of KB fibers in the concrete results in a significant increase in the tensile strength. Based on the results of experiments and undertaken statistical analyses using analysis of variance, 1.5% and 2% volume ratios were selected as optimal ratio for KWB and KB fibers, respectively.

The abandoned lead mine of Shahroud Gholleh Kaftaran at 4km northeast of the Chah Mousa mine contains significant resource of processing tailings left in the area. These tailings could be exploited with significant resource of over 50,000 tons with a copper oxide content of 0.95%. In this study, copper recovery from Gholleh Kaftaran mine processing tailings has been studied by agitated leaching and iron cementation methods. In the leaching experiments, pH and particle size had the greatest effect on copper dissolution, respectively, while solid percent and time had lower effect. In the coarser particles, the pH of the solution is not as effective as finer particle sizes as liberation and exposure of the malachite play the key role, here. The optimum conditions for pH 1, particle size of -106 microns, time of 150 min, and solid percentage of 30 were determined. The leaching recovery of 91.7% was achieved. Also, the effect of pH, temperature and time parameters on copper cementation was examined. The optimum condition of cementation was achieved at pH 1, time period of 30 minutes and ambient temperature. The efficiency of cementation in these conditions was 98.6%. The cemented copper powder was 96.9% pure with minimal iron impurities. The results of this research work demonstrates the potential of mine or processing plant tailings for extraction of their valuable contents.

The project management involves time management, cost, quality and risk of the project. Each project has time constraints, cost and quality. Since each of these constraints have a potential for risk, therefore, project risk management is essential. Increasing the cost and expanding the scale of projects on the one hand and increasing the uncertainty and risk of projects on the other hand has made risk management and assessment important. The purpose of risk management and assessment is to identify and evaluate accidental events that can have a positive or negative impact on project goals. In this study, a hybrid model for managing and evaluating the risks associated with tunneling operations using Multiple-criteria decision making methods is presented. After identifying the risks and performing the Delphi process, Risk Breakdown Structure (RBS) was used to categorize the risks , Analytical Hierarchy process (AHP) has been used for risk weighting, and VIKOR multiple-criteria decision making has been used to determine the risk ratings. The results showed that among the risks, the risk of manpower, Economic risk and management Risk were classified as critical risks.

In geochemical exploration studies, different anomaly separation methods, such as fractal methods and U-spatial statistics from the group of structural techniques, have been proposed for data interpretation and separation of anomalous zones. In this study,, these methods, were studied the spectral properties of U-values related to porphyry copper mineralization in Zafarqand region. The signals in the geochemical data and their variables indicate the status of the data variability in the location. To determine the variability of the U-statistics and to analyze its different frequencies, a new method was introduced and applied as the fractal method of the power spectrum– area of U-statistics. In this method, the U- statistics power spectrum data were divided into 5 different category, each of which belong to different frequency spectra. Multivariate principal component analysis method was used to determine the type of background or anomaly of these categories. Principal component analysis method was performed on the power spectrum matrix for the U values of all elements and for each category, separately. The results showed that Cu mineralization factor is present in frequency categories 1, 2 and 3 which also show low power spectrum values. These categories can be considered as categories of anomaly. The categories 4 and 5, based on principal component analysis, do not show a well mineralization effect. Therefore, these categories can be considered as background. Background frequency categories were filtered out of the anomaly categories and excluded from the data. Finally, the residual power spectrum was transferred to the location domain using the inverse Fourier transform and the anomaly map was obtained. In this map, the values are of parameter U and the location of the anomalies is well marked on it. The drilling results on these anomalies indicate the existence of deep mineralization.

According to the traffics of tunnels, the ventilation inside these underground structures is very important. A proper ventilation causes the contaminants from combustion of vehicles to decrease and provides better circumstances for breathing for the people in this limited space. The significant role that ventilation system plays in case of fire and dispersion of large volume of smoke inside the tunnel is another substantial reason for the necessity of utilizing appropriate ventilation system in the tunnel. In this research, the best ventilation system for Alavi tunnel, Shaid Rajaei town, Hormozgan is proposed. Using different standards, the necessity of utilizing mechanical ventilation system in there is determined and considering the advantageous of using longitudinal ventilation system, this ventilation approach is selected for Alavi tunnel. The required air flow and pressure drop to ventilate this tunnel are 155 m3/s and 93 Pa, respectively. Finally, according to the calculations, two jet fans from two separate company, Novenco and Korfmann is considered for the ventilation of Alavi tunnel. To compare these two jet fans better in case of fire, the tunnel is simulated separately for each jet fan in both normal and fire mode using Fluent software package. As a result, by comparing the outcomes from the software and considering the technical properties of each jet fan, the one from Novenco Corporation is proposed to use in Alavi tunnel.

In this paper, the fracture behavior of U-notched rock specimens under pure mode I loading has been investigated by means of a new criterion. The proposed approach is based on the maximum tangential stress (MTS) criterion which states that the onset of fracture takes place when the maximum tangential stress at the critical distance from the notch border attains a critical value. Due to the relatively large critical distance in quasi-brittle materials such as rock, the classical MTS criterion which considers only the first or singular terms of the stress series expansion around the notch border cannot provide an accurate estimation for the onset of fracture in rock-type notched samples. Therefore, it is proposed in this paper that the tangential stress component is determined directly form finite element (FE) analysis. Since the proposed approach is a combination of MTS criterion and the FE method, it is named the MTS-FEM criterion. In order to evaluate the MTS-FEM criterion, the experimental results reported in the previous studies for U-notched samples were employed. The comparison between the fracture loads predicted by MTS and MTS-FEM criteria and those reported in the previous studies revealed that the MTS-FEM criterion not only can provide more accurate estimates than the MTS criterion, but also in good agreements with the experimental results (less than 13%).