فصلنامه مهندسی معدن
پیاپی 52 (پاییز 1400)

Rare earth elements are generally separated from the leaching solution by concentration as a by-product of the processing plants. Among the main problems of their separation and extraction is the low level of them in the leaching stage. This study aimed to recover available rare earth elements from leaching solution of the non-magnetic sample of the Gazestan iron ore. The solution under investigation contained low concentrations of the rare elements cerium, lanthanum, neodymium, and yttrium, along with significant impurities including ferric ions, calcium, and phosphorus. Therefore, the removal of impurities, especially iron, were investigated. In this regard, it was tried to precipitate rare earth elements as fractional. The two main methods examined, 1) fractional precipitation of rare elements, iron and phosphate, and 2) precipitation of rare elements and calcium while increasing the solution temperature and remaining iron in the solution. Finally, the results of the two methods showed that rare earth elements were concentrated effectively. The REEs concentrated around two to three times higher than their initial level in the concentration step. After that, the adsorption experiments were performed on a batch scale by the Dowex50 WX4 cationic resin. Some experiments were also considered to investigate the effect of temperature enhancement on the adsorption of REEs on resin from the concentrated solution. As the temperature increased, the adsorption of the REEs from the solution increased significantly. In this case, the removal of iron was around 98%. The maximum adsorption of cerium, lanthanum, neodymium, and yttrium on the resin was, 99.11%, 98.67%, 99.0%, and 97.27%, respectively.

A mine closure plan is implemented while mine’s deposit is totally exhausted. It is necessary to precisely identify and analyze these factors and their impacts on mine’s life. In this research, with the purpose of identifying and analyzing the factors affecting the premature closure of Chadermaloo Iron ore mine, a comprehensive risk closure model of Chadormalou mine was developed based on the Laurence’s closure risk model. With this respect, in order to assess the probabilities and consequences of broad and sub-issue closure risks, questionnaires have been provided and distributed through the seven experts in case study mine site and filled questionnaires based on experts’ judgment collected to obtain certain values of risks. In the next step, identification and ranking of the factors affecting the premature closure of surface mines was designed in a hierarchical structure in order to predict and take appropriate measures. The model at the level of criteria includes four main components consists of probability of occurrence, consequence, uncertainty of estimation and ability of the organization in responding to risk. The alternatives comprises risk factors in the social, political, economic, environmental, legal, technical, safety and health issues. Whole calculations were performed in accordance with Chang approach through Fuzzy Analytical Hierarchy Process (FAHP) to evaluate and rank relative and final weights of each criterion involved in premature closure risk assessment. The results of application of closure risk model to Chadormaloo mine demonstrated that the mine is classified as "moderate" from premature closure point of view. The closure probability of 30 percentage shows the mining activities are able to be continued. This implies more attention should be paid to eliminate or minimize the impacts of these issues within mine’s planning and design.

Long-term production scheduling in open-pit mines is a crucial issue in mining planning and determines the distribution of cash flow throughout the life of the mine. The purpose of the planning is to maximize the net present value by taking into account all operational constraints such as slope, mixing of different grades, mineral production, and extraction capacity. The uncertainties associated with model data play an important role in optimizing long-term production plans. Among the uncertainties, grade uncertainty plays a major role. In this paper, hybrid models are presented by the Lagrangian relaxation (LR) method, augmented Lagrangian relaxation (ALR) method, and firefly algorithm (FA) to solve the long-term production scheduling problem of open-pit mines with the assumption of deterministic and also considering the grade uncertainty. The firefly algorithm is used to update the Lagrange multipliers. The newly proposed approaches are based on optimizing Lagrangian multipliers and comparing them with the results of combined Lagrangian relaxation method and augmented Lagrangian relaxation with the Genetic Algorithm (GA), and the traditional sub-gradient (SG) method. For solving and validating the obtained model, Chadarmelo iron ore mine is considered as a suitable case study. The results of the case study show that the combined strategy (ALR-FA) can provide a near-optimal solution over other methods such that, over a given period, the net present value using the proposed hybrid approach is 20.11% higher than the traditional method is available. Also, the CPU speed of the proposed model is 4.7% more than the other methods.

Production planning in underground mines is still a manual process and there are no suitable tools for optimal production planning for these mines. It is impossible to achieve a real optimum result through manual programming because of the complexity of underground mines and production planning problems in these mines. Due to the increasing consumption of minerals on one hand and the depth of mineral reserves, on the other hand, efforts to achieve comprehensive production planning optimization methods in underground mines and especially large-scale production methods with high production rates are inevitable. Among the underground mining methods, sublevel caving is a common method for hard rock mining, and there are very few studies of long-term production planning for this method. In this paper, a new mathematical model with the aim of maximizing the net present value (NPV) is presented to optimize the production planning of the sublevel caving method. The technical and operational constraints of the sublevel caving method such as development constraints, production capacity, sublevels geometry, and storage access are included in this model. The proposed model was implemented on an economic block model and the maximum NPV was determined. A comparison of the results obtained with the results of manual planning shows a significant increase in NPV mining operations.

The porphyry copper deposit of Daralu is located 130 km south of Kerman province and in the metallogenicall zone of Dehaj-Sardouiyeh. The estimated Mineral storage of the deposit until 2019 is 294 million tons with an average grade of 0.35% Cu. The study of lithogeochemical zonality indicators is used to identify the type of deposit, determine the location and depth of the ore body. In this study, standard lithogeochemical zonality indicators that are used to identify the position of the world's porphyry copper deposits were compared with each other in the Daralu porphyry copper deposit. Among these indicators, the Cu/Mo zonality index and then the (Zn*Pb)/(Cu*Mo) show legal behavior Compared to other indicators, and their trend is steadily declining from surface to depth. Based on the numerical values of the zonality index (Zn*Pb)/(Cu*Mo) for the standard porphyry copper deposits, the ore body in Daralu deposit is located at an absolute height of 2950 to 2750 meters and the depth of the sub ore primary lithogeochemical haloes of the deposit were determined from 2750 to 2550 m. However, based on the numerical values of the Cu/Mo index, the final depth of the sub ore primary lithogeochemical haloes was estimated at 2425m, although the results of both indicators confirmed each other and overlapped. Also, by using the linear lithogeochemical productivity of the elements in different horizons, the lithogeochemical zonality sequence of the elements was calculated in the form of Mo-(V,Co)-Au-Ag-Ni-Pb-As-Sb-Cu-(Zn,Cd,Mn) from the depth to surface. The highest molybdenum value belonging to the absolute height of 2550 meters (the deepest part of the deposit) and the highest amount of lead were recorded at absolute height of 2950 meters (deposit surface). Indices and sequence of elements was determined that the supra ore is washed away and mineral mass is close to the surface.

A reliable estimation of the discontinuity orientation of a joint set is of great importance in rock mechanics studies and interpretations. Common approach for determination of the joint set orientation is based on deterministic approach without considering the reliability of calculations. Nowadays, statistical and probabilistic methods are widely used to investigate uncertainties in the input data as well as validating the output of calculations and outputs where the emphasis is placed on identification of unknowns in analyzes. In this study a new method was presented for calculating the representative discontinuity plane of a joint set based on the Monte Carlo simulation method and the results were then compared with the conventional method. Evaluation of deterministic and probabilistic methods were carried out using distinct element method which showed that the proposed method is more suitable compared to the conventional method due to enhanced reliability in calculation as well as simulating based on considering the statistical distribution function and sampling from them. This advantage can be clearly seen for orientations fall in the edge of hemisphere projection. Furthermore, results of this study showed that when the joints are located on one side of the stereonet, the conventional method has a reliability more than 98%. in determining the dip and dip direction of representative discontinuity plane of a joint set while for orientations fall in the edge of hemisphere projection the reliability is reduced to more than 95% for the dip direction and more than 87% for the dip.

Mechanized tunneling in hard rock is associated with various challenges and risks, one of which is the penetration rate of Tunnel Boring Machine and the occurrence of grinding and chipping in various conditions. When the strength of the rock is high and the amount of jointing is low, the penetration rate of the machine is reduced and instead of forming rock chips in the tunnel face. In these conditions, which is called grinding, tunneling is associated with wear and high consumption of cutting tools as well as a severe reduction in the efficiency of excavation operations. In this paper, the boundary between grinding and chipping processes is investigated and a criterion for determining the minimum normal force in different geomechanical conditions required to create chipping condition is presented. For this purpose, data related to Kerman Water Tunnel and Southern extension of Tehran Metro Line 6 tunnel are used. In this regard, by comparing the normal forces on the cutting tools and the resulting penetration rate, the threshold for changing conditions from the grinding phenomenon to chipping is determined. The results show that the amount of normal force required to be applied by the disc cutter to the rock mass to excavate under the chipping conditions for rocks with medium, high and very high uniaxial compressive strength are equal to 130, 210 and 225 kN, respectively. Moreover, by examining the data of Metro Line 6, the role of joints in providing the conditions for chips formation was investigated and the result showed that the boundary between grinding and chipping for medium strength rocks can be at RQD=75%. It was also found that with the penetration rate exceeding a certain threshold, a slight increase in normal force causes a significant increase in the penetration rate, which increases efficiency and reduces operating costs.