فصلنامه مهندسی معدن
پیاپی 49 (زمستان 1399)

In this study, the feasibility of improving the flotation circuit performance of a phase 1 of Sungun copper plant was investigated. For this purpose, circuit performance was first monitored ., It was found that in the rougher stage the some copper exists in fractions greater than 106 and smaller than 38 microns was lost. Final concentrate analysis taken on different days showed that the copper grade decreased due to the iron content increasing. Mineralogical studies also confirmed the maximum presence of pyrite in the final concentrate. Field surveys of the flotation circuit showed that there are many technical problem in the circuit that affect on the flotation process. These drawbacks including the presence of thick tubes at the surface of the re-cleaner cell, the lack of a standard pattern of wash water distribution and jet spraying. Measurement of pH in different points of the circuit showed a decrease of pH below 11 and so hydrophobicity of pyrite caused. Measurement of operating variables in the circuit showed that the wash water rate and gas rate used in the circuit were higher and lower than the values suggested by the researchers and the designer, respectively. Due to the deficiencies identified in the performance evaluation phase, laboratory tests were designed and performed in two stages using mechanical flotation cell and column flotation cell. Adjusting the gas rate and the wash water rate at the laboratory scale at the intervals suggested by the researchers resulted in the increase in 3% grade and 10% recovery.

Hydraulic fracturing based on the use of guar gum water-base fluid with appropriate viscosity has been recognized as a viable solution for extracting oil and natural gas from the reservoir due to its unique benefits such as low cost and proppant carrying capacity. However, the lack of knowledge of reservoirs fractures has challenged field applications. Therefore, the purpose of this study was to investigate the effect of fluid injection rate on fracture pressure and geometry of fractures. To achieve this goal, a series of hydraulic fracturing experiments were performed on limestone rock samples using a guar gum water- base fluid. To investigate the effect of fluid injection rate, CT scan technology was also used to describe the geometric parameters of the fracture. The results of experiments show that with increasing fluid flow rate injected from 1 to 6 ml/min, breakdown pressure and fracture opening increase. As the volume of consumed fluid increases the breakdown time decreases. The findings of this study reveal that low guar gum-flow rates can create a better inter- connected fracture network than higher flow rates.

Traditional deterministic evaluation of geotechnical problems has long been considered insufficient since the uncertainties inherently associated with geotechnical materials cannot be considered explicitly. This is especially so for underground problems where not only the properties of rocks or soils but also the in situ stress conditions cannot be accurately estimated. This requires the development of reliability analysis for tunnelling problems. System reliability analysis of tunnelling problems is illustrated by using an iterative closed-form formulation for a circular tunnel reinforced by end-anchored rockbolts. Three performance functions, namely,the mobilized tensile force in the rockbolt, the maximum displacement and the plastic zone size of the tunnel, are considered. İn this paper, the RT software is applied to an iterative closed-form solution for a circular tunnel reinforced by rockbolts, which was proposed by Bobet and Einstein (2011). The developed surrogate models were implemented into the first-order reliability method (form), second order reliability method and Monte Carlo Simulation (MCS) to evaluate the stability of tunnels reinforced by rockbolts.

The influence of clay minerals on flotation performance has been extensively studied by making synthetic samples with different percentages of clays but the impact of a mixture of clays in an ore and the effect of available clays on the ore itself has not been studied. The presence of a combination of clay minerals in the feed of the Sungun Copper Concentration Plant causes various problems such as reduction of grade and recovery of final concentrate. It is evident that understanding the behavior of clays in flotation performance of this ore can be an effective step in improving plant operation for feeds with high percentages of clays. Therefore, in order to investigate the influence of clay minerals on the flotation performance of Sungun ore, the flotation behavior of two samples with different clay percentages was investigated in the rougher flotation step. The obtained results indicated that for the sample with low clay content, 6.12% of illite and 2% of kaolinite, there is a reduction in the recovery and froth bubble size. On the other hand for the sample with high clay content, 100.46% of illite and 2.36% kaolinite, the volume of froth decreased but there was not reduction in the final recovery. Illite had no effect on flotation process and observed difference was related to the percentage of muscovite mineral in two samples (6.62% and 11.13% for high and low clay samples, respectively). Increasing clay minerals to more than 10% increases pulp viscosity. The addition of kaolinite by 20% by weight reduced the number of large bubbles and discolored the foam, reducing the recovery from 81.25 to 71.43% and grade from 5.38 to 2.5%.

Large and complex underground projects comprise of many excavation parts and require a relatively long construction period. Design and construction of such projects need a thorough analysis of many information including borehole logs, cycle time, requirements of equipments, the arrangement of multiple excavation faces along the project’s time-line, and the arrangement of equipment allocation among multiple faces. The result of this analysis should yield an optimum construction time and the required strategies to manage this period. This paper explains some methods to conduct such analyses to evaluate a geological model, the details of a cycle time, the strategy to evaluate the total construction time and its optimum value, and the strategy to optimize the equipment allocation. The results of these methods are beneficial for the projects’ engineers to reach to a better evaluation in the design phase of a project (e.g. bidding time) and to plan a better construction management strategy during the construction phase.

Cross-gradient based joint inversion method is one of the very useful methods for reduction of non-uniqueness and elimination of lacks of reconstructed models using separate inversion. This method have also some deficiencies against its advantages. It needs too much time when the dimension of problem is large and sometimes it's not runnable. In this paper data space method, as a fast procedure for inversion of some matrices in inversion process, was represented and cross-gradient based joint inversion algorithm supported by this method was developed in MATLAB software. To investigate the capability of code, a synthetic model include three cubes with various dimensions and depth extend was used. At first the calculated gravity and magnetic anomalies of this synthetic model were separately inverted using data space inversion method. Then these synthetic gravity and magnetic data were jointly inverted using the improved 3D inversion algorithm along with smoothness constraint. The obtained results showed significant improvements in the output model with the same conditions of separate data inversion. These improvements were in delineation of location and depth estimating aspects and also capability of code performance to recover such number of model’s parameters. After validating of results, the proposed routine was applied for 3D joint inversion of the gravity and magnetic data of one Hematite area around Jalalabad iron mine in Zarand city (Kerman province). Comparison of the inversion results with those obtained by drilling, validates correctness and ability of the presented algorithm even when we encounters with deficiency of data.

Industrial development and their requirement for mineral caused the mines to put higher annual production capacities in their production plans. Large-scale production requires production planning that use the realistic and efficient operational objective and constraints into models. According to various effective parameters in the planning and their relation in the successful operation of block caving complicated the scheduling of such mines. In this study, by introducing drawpoints activity period constraints and the number of active drawpoints in each period of mine life is researched the control of the start period of drawpoints and the caving process in the mining area. For this purpose, the MILP model has been developed using MATLAB and solved in CPLEX software. Implementation of these models on 109 drawpoints on 13 periods of mine life showed that the proposed MILP models controlled drawpoints activity and maximize economic productivity. The resulted showed that the maximum difference in NPV calculated in different directions is 16%, so the models respected the objective function. The results of production scheduling for the drawpoint 65 showed that in SN direction start period was 1 and the lifetime 3 years, so 33% of its tonnage is drawn every year. However, in the NS, the start period was 8 and lifetime was 1 period; therefore, the activity period of the drawpoints related to the tonnage and grade and also the direction of caving.