فصلنامه مهندسی معدن
پیاپی 11 (بهار 1390)

During the drilling of Nousoud tunnel in the west of Kermanshah Province (Iran), much hydrocarbon seepages spilled from the fractures and walls of the tunnel. In order to evaluate and assess hydrocarbon source rock potentiality, a detailed geochemical study was carried out on Pabdeh, Gurpi and Ilam Formations in Nosoud tunnel and Garu Formation in Pataqe#1 and Imam Hassan#1 wells in the west of Kermanshah. A total of 22 cuttings and 9 core samples were subjected to geochemical investigations. The result of the primary assessments using Rock-Eval pyrolysis technique, vitrinite reflectance measurements elemental, clay minerals, chemical analysis and molecular (biomarkers) studies (GC, GC-MS), showed that Pabdeh Formation (lithologically composed of marl and argillaceous limestone) has poor potential for hydrocarbon generation. Maturity of the studied formation is in the early phase of catagenesis and exhibits Types II and III kerogen. Pabdeh formation was deposited in marine anoxic environment. Whereas, Gurpi formation in Nosoud tunnel and Garu formation in Pataqe#1 and Imam Hasan#1 wells exhibit fair potential for hydrocarbon generation and their maturity is in the peak and late phase of catagenesis. These formations have mixed Type II and III kerogen which were deposited in marine anoxic environment and are lithologically composed of shale and argillaceous limestone. Having reservoir characteristics and carbonate lithology, Ilam formation doesnot seem to be a potential source rock (high measures of TPI & S1 plus worthless measures of S2). The findings of this study showed that Gurpi formation along the tunnel and Garu formation in more depths are good sources for hydrocarbon seepages in Nousoud tunnel and the neighboring areas.

Coal mining changes the original geochemical equilibrium of rock bodies and by changing the oxidantion condition of the area; it may cause the release of elements from the coal and ambient rocks into the environment. In the present study, the effects of mining activities in Tazareh Mine Complex, located on 70km North West of Shahrood, were investigated. Concentrations of As, S, Cu, Fe, Hg, Sb, Pb, Zn, Sr and Se in the water resources, tailings and the coals excavated from the main tunnel of the mine were determined to find out the distribution of these elements in the groundwater. The coal in this region shows a high value of enrichment factor for Cu, Pb, As, Hg and Se (22.55, 77.01, 17.86, 44.64, 61.95, and 486.40, respectively). The tailing and face have much less enrichment factor for the above mentioned elements compared and the coal in the region. In terms of correlation among the elements, high correlations between Fe and Pb (0.929) and also Zn and Hg (0.980) were detected. Heavy elements in very low concentrations (3.1 and 2501 ppb for Cu and Sr, respectively and less than the detection limit for Pb, Zn, Fe, As, Sb, Hg and Se) were detected in the mine drainage due to Natural Alkaline Mine Drainage (NAMD) with pH=7.6. Mining, however, caused an elevation in the concentration of S, Sr, Cu, As and Se (430000, 8505, 3.7, 1.5 and 3 ppb, respectively) in the groundwater. S, with a rise of 9.4 times in the downstream groundwater comparing to the upstream groundwater, showed the highest increase.

The tailing dam of the Sarcheshmeh copper mine (Kerman, Iran) contains elevated concentrations the heavy metals. Therefore, the sediments of the Sarcheshmeh copper mine were analyzed in order to determine the contamination of heavy metals and the contamination intensity. In fact, the aim of this research was to evaluate the rate of heavy metals contamination (Co, Mo, Zn, Cr, Mn, Ni, Pb, Ti and Fe) in the sediments of Sarcheshmeh copper mine, which conduce to the tailing dam. In this paper, the contamination indices comprising contamination factor, pollution load index, enrichment factor and geoaccumulation index were used to evaluate the heavy metals distribution in the sediments of the area. The amounts of Enrichment Factor (Cobalt: 0.95, Copper: 16.63, Molybdenum: 3.84, Zinc: 1.95, Chrome: 0.87, Manganese: 1.27, Nickel: 0.36, Lead: 1.62, Titanium: 0.83 and Iron: 10.01) and the concentrations of heavy metals were evaluated by considerable number of samples. With respect to the calculation of Geoaccumulation Index for the heavy metals, the metals like Cu, Zn and Fe (Zn>Cu>Fe>Mo>Pb>Mn>Cr) stood in the pollutant limit. Correlation coefficient and hierarchical analysis were used to determine the source of sediments, dispersion pattern of metals and the environmental evaluation for the present situation. The results obtained from the geochemical studies, correct multivariate statistical analysis and calculation of contamination indices, enrichment factor, geoaccumulation index, contamination factor and the pollution load index verified the high concentrations of these metals. The results of the factor analysis and hierarchical analysis (rate of heavy metals limit) on the sediment samples of the study area are completely consistent with the results of the calculation of the Contamination Factor for the sampling stations.

Simulation techniques are used to evaluate and optimize the mineral processing circuits. In this research, comminution softwares including COMSIM and BMCS and MODSIM were used to simulate the performance of Se-Chahun ball mill circuit. First the samples were taken from the ball mill circuit, in order to determine the size distribution, solid percent and flowrate of the feed and products. Then breakage and selection functions of the ball mills fresh feed samples were determined using BFDS software. Also, the parameters of the breakage function empirical model and Austin selection model were determined. The residence time distribution of the ball mill circuit was measured using salt tracer. Then those parameters of the hydrocyclone models of Plitt and Nagswararao were determined. Finally, the ball mill circuit was simulated using the above-mentioned three softwares. The comparison of the simulation results with the measured data of the plant showed that all the softwares could predict the circuit performance with high accuracy, although the MODSIM was superior.

A hydrocyclone unit in a mineral processing circuit can be selected based on different procedures. Because of the coal nature, selecting a hydrocyclone in the coal washing circuit is a complicated process. The third correction factor (particle density) plays an important role in this area. In the present research, the underflow of Zarand Coal washing thickeners as hydrocyclone feed was monitored. Then the third correction factor of hydrocyclone was modified. Finally, the hydrocyclone diameter was calculated as 37 cm.

In Aghdareh gold processing plant, grinding circuit product size has a significant effect on downstream gold leaching process. Therefore, the performance optimization of hydrocyclone package in order to decrease the size of overflow stream to less than 70 μm (present value) will considerably increase the gold recovery. In this research, optimization of Aghdareh’s hydrocyclone package performance was done by application of Plitt’s model and its calibration and simulation of classification process. Two plant sampling campaigns were carried out to collect samples from the streams around the hydrocyclone package. Screen analysis tests were performed to obtain particle size distributions (PSD). Then, measured PSD and flow rates of various streams were adjusted using NorBal data reconciliation software. Then, BMCS (BMCS-based Modular Comminution Simulator) was used to predict the PSD of overflow and underflow streams for the first sampling campaign and also calibrating Plitt’s model to operating Aghdareh hydrocyclone package. Then, BMCS simulation predictions based on the calibrated Plitt’s model were validated using the second sampling campaign. The simulations showed that by using vortex and spigot internal diameters equal to 75 and 70 mm, respectively and with 6 operating hydrocyclones, the P80 of the overflow product can be decreased to 68.5 μm. Also, simulations by using vortex and spigot internal diameters equal to 94 and 53, respectively with 6 operating hydrocyclones showed that the separation sharpness, m, can be increased from 1.18 to 2.81 which indicates a 2.38 times increase in classification accuracy.

Due to uncertain nature of tunneling projects, risk assessment can be considered as one of the most important managerial aspects in which resource allocation optimization is almost satisfied. Evaluation, ranking and clustering of the risks, which is performed on the basis of some specific criteria, provides a proper environment in responding to the possible risks. In this paper, identifying risks and their respective criteria of the risks of tunneling activities in Seymareh dam project (Iran), importance of each of the risks was determined using Elimination and Choice Translating Reality (ELECTRE) method. The collection and aggregation of the expert judgments were performed on basis of group decision-making and weighted average technique, respectively. According to the obtained results, the project risks are classified in 8 clusters and the most critical cluster involve economic, owner and technical risks.

Mapping the geometrical parameters of natural fractures is very important in evaluation of hydrocarbon reservoirs. Since subsurface feature properties differ from fracture parameters detected from outcrops, the best way for modeling the fractured reservoir is using imager tools. Imager tools such as Formation Micro Imager (FMI), with appropriate resolution in detecting even small-scale discontinuity features, may help conceptualization of fractured reservoirs. The FMI presents virtual images from the walls of well based on the differences in electrical resistivity between the formation and the drill mud. One of the important applications of FMI log is detection of open and close natural fractures. In this study, using recorded data of open fractures in a well, firstly the best fitted density functions for the geometric parameters of fractures were recognized. Using the distribution function of geometric parameters of fractures and Monte Carlo process, a numbers of Discrete Fracture Network (DFN) models were generated. The most realistic DFN models fitting with the mapped fracture patterns in the well were identified using William-Watson (W-W) statistical test. The results of this research may be used for numerical modeling of fluid flow into DFN, studying of permeability tensor and modeling of production rate in deep hydrocarbon reservoirs.

With regard to the types of risks existing in tunnels, geotechnical risks play an important role in the selection of tunneling method and machine types. Also, in order to prevent some geological and geotechnical hazards during tunneling, selecting the most appropriate tunneling machine is very important. In this research study the main geotechnical hazards of tunneling by Roadheader with their common mitigation measures were specified. At present, three Roadheaders are excavating the three drifts of the Tabas coal mine in Iran. Hence, the above drifts were used in this research study. The risk assessment matrix method in these tunnels showed that there is a lower risk of tunneling by Roadheader than utilizing the drilling and blasting method. The determined geotechnical risk assessment also showed that the transverse cutter head is more suitable in comparison to a longitudinal cutter head for such tunnels. Then by using an instantaneous cutting rate model, the cutter head power of the Roadheader was determined. According to the model, a light weight Roadheader with a cutter head power of about 80-110 Kw and 40 ton weight are suitable. Finally, the four types of manufactured Roadheaders which their specifications were similar to the determined ones were selected.

Nowadays, convergence-confinement method is one of the most important methods in determining support systems for both underground circular and non-circular spaces. Selecting an appropriate constitutive model including elastic-perfectly plastic, elastic-brittle-plastic and elastic-strain softening models has a significant role in the application of this method. In some cases, the difference of displacements resulting from choosing different constitutive models is more than 100%. In this research, we attempted to investigate the effect of different constitutive models on the ground reaction curve and plastic zone made around a circular opening. It has been supposed that a rock mass is initially carries an elastic behavior and undergoes an isotropic pressure,. The failure criterion used here is non-linear Hoek-Brown yield criterion. The problem is solved in a stepwise procedure proposed by Brown et al (1983), in which rock mass strength parameters change in a stepwise method from the peak to the residual values. Finally, a sensitive analysis is performed on the Hoek-Brown strength parameters.