JOURNAL OF ANALYTICAL AND NUMERICAL METHODS IN MINING ENGINEERING
Year:2016 | Volume:6 | Issue:11 |Papers Count:9

In this paper, Graphical Evaluation and Review Technique (GERT) network analysis technique used in exploration project management for anomaly separation methods and a suitable model will be created by combining two methods of fractal geometry and U spatial statistics. In mineral exploration project (according to situation of geology, geological structure and mineralogical at mineralization area and because of probabilistic nature of them), Fatal mistakes can happen when starting exploration activity for anomaly separation. Spatial invariance and frequency distribution of samples are the most characteristics of geochemical data to determine the isotropy or anisotropy variation. Since these projects consist of various uncertain and probable activities that may be repeated frequently, we can model those processes as stochastic networks such as GERT network. Therefore, in mining activities GERT networking is applied frequently, and certainly led to increase the accuracy and performance of the process. This study is mainly focused in the Cu-Au Northern-Dally porphyry deposits that are exposed within the Urumieh-Dokhtar Magmatic Arc. The concentration–area (C-A) fractal model (based on Fractal dimensions) and moving average technique (U special statistic; based on window size ore search radius) have been used for decomposition and separation of anomalous patterns of geochemical data. So the probability of performing a lot of activities already in fractal geometry, reproducibility of a set of activities in U-spatial statistic, or probability of select one of these methods according to exploration project just interpreted with GERT networking. The result of combining these networks is implemented and show similar result with high overlapping to recognize anomaly area. With step by step implementation of possible activities for each method, Au and Cu show high overlapping in different populations. This finding implies to the precision and accuracy of fractal and U- spatial statistics. Third population with highest dimension and maximum degree of populations break-point in fractal geometry shows that values >560 ppb for Au and >1700 ppm for Cu are distinguished as anomalous data. While, U- spatial statistics indicate the value higher than average+ one standard division (Ū+S) equal to 1.47 (>500 ppb) for Au and equal to 1.45 (1650 ppm) for Cu are the threshold value for anomaly population.

Summary: Spectral Induced Polarization (SIP) is widely used for environmental and hydrogeophysics, but one major limitation concerns the electromagnetic (EM) coupling effect. In this study, an overview of the mutual impedance of a polarizable multilayered homogeneous half-space is done (it consist both of electromagnetic coupling and the Spectral Induced Polarization effects). Then, the effect of electrode array parameters and the subsurface electrical resistivity on mutual impedance response is investigated. The results show the EM coupling effect can be seen at frequencies less than 10 Hz. It will increase with increasing frequency of excitation current and the conductivity. So by choosing the optimal arrangement for current cable, SIP can be surveyed using electrode arrays such as Schlumberger electrode array (with higher signal to noise ratio) and the EM coupling effect is also reduced as much as possible. Introduction: Induced polarization (IP) is the main geophysical method in mineral deposits prospecting. Spectral induced polarization (SIP), an extension of the IP method, in the past few decades has been used extensively in mineral prospecting and increasingly in environmental investigations, hydro-geophysics, archaeo-geophysics, bio-geophysics. SIP measurements are very sensitive to the low frequency capacitive properties of rocks and soils. One of the major limitations of SIP method is the EM coupling effect. In SIP method, the amplitude and phase components of the earth’s resistivity are measured in a frequency range (typically 0.001 Hz to 10 kHz). At low frequencies, the inductive coupling effect may affect the spectrum ohmic responses and normal polarization effect of the subsurface material. In SIP, there are three types of the EM coupling effect: the first is the removal of the EM coupling effect from SIP field data. In the second type, the mutual impedance of the earth is calculated using Cole-Cole equation as IP dispersion of the earth. SIP data and mutual impedance are compared using an inversion algorithm in order to recover the earth IP parameters. In this method, since the SIP method employs alternative fields using grounded wires, it should be characterized as an EM method. The third uses a current cable arrangement in order to reduce the EM coupling effects from SIP data. Due to the increasing application of SIP method during the recent years, investigating and finding solutions to its limits is necessary. Because in this method, time-varying current signal is used, electromagnetic coupling occurs between the Earth, current cable and potential cable and electrical response affected by this phenomenon. So the calculation of earth's mutual impedance response and the separation of earth's electrical and electromagnetic responses are necessary. Methodology and Approaches: In this study, an overview of the electromagnetic coupling effect on the Spectral Induced Polarization data and calculating this effect on the total response using linear dipole-dipole electrode array with dipole arbitrary length on a polarizable multilayered homogeneous half-space is done. Then, the effect of electrode array parameters and the subsurface electrical resistivity on mutual impedance response is investigated. We used CR1D mod code in order to calculate the mutual impedance of the earth (it consists both of SIP and electromagnetic response of the earth). At the end, the effect of current cable arrangement on electromagnetic coupling and mutual impedance response is investigated.Results and Conclusions: The results show that the electromagnetic coupling effect can be seen at frequencies less than 10 Hertz. The induced impedance response will increase by increasing the survey's dipoles length as well as increasing the distance between the two consecutive dipoles. So we can conclude, when electrode array is pole-dipole, pole-dipole and linear Schlumbeger, the electromagnetic coupling effect will be much larger when electrode array is dipole-dipole; if the rectangular arrangement is chosen for current cable, the Schlumberger electrode array with low signal to noise ratio is used for SIP survey. On the other hand, the EM coupling effect will increase with increasing frequency of excitation current and the conductivity. So by choosing the optimal arrangement for current cable, SIP can be surveyed using electrode arrays such as Schlumberger electrode array and the EM coupling effect is also reduced as much as possible.

Summary: The aim of this research is stability analysis of coal pillars in inclined coal seams (the variable pillar width and the variable seam dip) using the finite difference method software (FLAC2D). This aim is achieved by assessing the vertical and shear stresses distribution and their influence on the coal pillar.Introduction: In some mining method such as longwall, room and pillar and stope and pillar, the design of mine is done in such a way that the pillars are left in the seam gradient. Therefore in this case the effect of seam dip must be considered on the stability of pillar. Pillars in dipping strata are under in compression and shear load and therefore require consideration of a failure criterion that accounts for compression and shear load. The stability analysis of coal pillar can be performed by empirical, analytical, statistical and numerical methods.Since the existing empirical methods developed to pillar design have some limitations, the application of numerical methods was widely increasing to optimize pillar size in all mining methods. Applying numerical methods, it is possible to consider seam dip on the stability of coal pillar.Methodology and Approaches: In this study, six numerical models were analyzed in FLAC2D software for 30, 45 and 60 degree steeply coal seams with 10 and 15 m pillar width. It should be noted that 90 m width are considered for stopes in all numerical models. Moreover, exploitation has been started at the first stope and then continued to the second stope. In each step of the analyses, the model is run to equilibrium before creating the second stope.Results and Conclusions: The numerical modeling result on 30, 45 and 60 degree steeply coal seams with 10 and 15 m pillar width showed that the vertical stresses on the pillar decreased by increase of coal seam dip and coal pillar width. Moreover, the shear stresses increased by increases of coal seam dip. Finally, according to the numerical modeling result the pillar width of 15 m on a dip of 30 degree is stable.

Underground coal mining has always known as one of the most hazardous mining activities. The risk of possible incidents in these mines may cause the irreparable damages such as death or personal injury, damage and loss of equipment or interrupting the production process of mines. For this reason, the risk analysis has a very important role in underground coal mines. Hazards identification is the first step of a risk analysis process. In this research by using a combination of library efficiency and expert judgment, the most important hazards in lonwall coal mining have been identified. The prioritization of identified hazards is done by using fuzzy TOPSIS. For this aim the likelihood, severity and reaction was considering as a main criteria and vulnerability and detection as the sub criteria. The results show that the severity and reaction by weight of 0.416 and 0.293 respectively has the highest and lowest impact on the hazard ranking. The proposed model was used in Tabas longwall coal mine. Results show that the roof fall at the panel face and gates by similarity index of 0.832 and 0.823 is the most important known hazards. Also, the subsidence and flooding by similarity index of 0.492 and 0.482 has the minimum level of similarity index. To determine the sensitivity of the achieved ranking, a sensitivity analysis was conducted. The results show that the proposed model has no sensitivity to the weight of decision criteria.

Mine and deposit are the one of the major part of economic fundamentals in any country. Sistan and Bloochestan located in the south-east of Iran has the noticeable and mineable deposited. Chromite's reserve is the considerable potential for development in this province.By attention to the reserve of Chromite in Sistan and Beloochestan province Manufacturing and running a mineral processing plant for Chromite is necessary. This research is carried out for Site selection of Mineral processing plant for Chromite in Sistan and Beloochestan province.The research method in this article is practical by looking to aims and surveying based on the data collection methods. The research were carried out by using of Groups AHP and SAW methods and BORDA combined method. By helping of fifteen members of university and industrial expert in mining technology, also by data collection of government offices, For selected the best selection eight criteria were investigated after nomination the suitable selection.Zahedan was selected by Groups AHP and SAW methods. It is using of the multiplied Borda method for the better judgment and multiplied these methods. Finally Zahedan was recognized as the best place for manufacturing and running a mineral processing plant for Chromite.

Summary: The dominant mechanism in the High Pressure Grinding Rolls (HPGR) is compressive breakage. A laboratory scale experiment could be implemented to study the compressive mechanism. In the present research, for the first time in Iran, the piston and die device consists of controllable hydraulic press (P&D test) were utilized at Golgohar complex to study the compression breakage. This test was applied to investigate the edge recycle effect on the HPGR performance. Introduction: The usage of HPGR in the iron mineral processing plants is extending in Iran. Edge product of the HPGR is coarser than the central product that is not favorable for downstream processes. It is imaginable that the HPGR performance could be controlled by separating and circulating the edge materials. Before any mechanical changes in the industrial HPGR machine at the 4th train of iron concentrate plant in Golgohar, it was necessary to investigate the edge recycle effect fundamentally. From operational point of view, the HPGR in pilot scale is required for feasibility study, investigating the variables and predicting the associated operational advantages of any changes. The pilot plant scale of HPGR is not available at Golgohar complex. Also, conducting the pilot scale experiment requires a significant amount of samples, which is costly and time-consuming. In both cases, fundamental and operational researches, the simple, available and knowledge-based laboratory tests are required. In addition, the laboratory tests play an important role in understanding and prediction of variable behaviors in industrial scales. Methodology and Approaches: A laboratory method was developed to study the effect of the edge product recycling. After designing and constructing of the piston and die system, compressive breakage tests were conducted at the pressure of 1730 bars using samples taken from the feed of the 4th train of the concentrate plant. For separating the central product from the edge product of the experiments, a punch system was designed and constructed. To obtain the effect of edge product circulation, this material was mixed with the fresh feed at the ratio of 0.8. The sample was compressed at the same pressure. The D50 of the product was reduced by 25% with the edge product recycle. Particles from test product were studied using optic microscope and scanning electron microscope (SEM). Also a numerical method (trapezoid formula) was implemented to calculate the compressive breakage specific energy. Results and Conclusions: Study of piston and die test cake product particles using optic microscope and scanning electron microscope (SEM) showed that just a few numbers of particles have surface micro cracks. Therefore, circulating the edge product will increase probability of particle breakage or crack creation. Finally a flowsheet was proposed which allows circulating the edge product of the industrial HPGR at the 4th train of the concentrate production of the Golgohar complex. Also the compressive breakage specific energy was obtained by a numerical method named trapezoid formula using force-displacement graph. This graph was attained from piston and die test data.

Hydraulic fracturing is one of the most well-known methods in stimulation and enhanced recovery in oil and gas reservoirs. Determination of propagation path of hydraulic fractures (HFs) and created fracture network have a dominant role in increasing permeability of the reservoir. Reservoirs contain many natural fractures (NFs). Understanding the interaction behavior of the HF and NFs controls the fracture network created by the HF propagation. In this paper, a higher order displacement discontinuity method is uaed, the numerical model is verified by several analytical well-known problems in fracture mechanics. Three main behaviors may be named for the interaction of HF and NFs i.e. arrest, crossing, and opening. Two well-known interaction criteria are introduced. Then an algorithm is introduced to determine interaction of HF and NF. The algorithm and its implementation in a numerical model were tested against experimental results. Using higher order displacement discontinuity method the interaction of HF and NFs is investigated in various conditions. Results showed that the possibility of crossing for higher angle of intersection is higher. Also the HF energy reduces after each NF crossing. It means that HF has lower chance for crossing NFs after previous crosses.

Summary: Mining production planning is a very vital subject of mine design process. One of the most important issues in mine production planning is the cutoff grade which is simply a grade used to distinguish between ore and waste. Waste materials may either be left in place or sent to waste dump. Ore is sent to the mill for further processing. Lower cutoff grade causes higher amounts of ore to be processed and subsequently lower amounts of waste materials to be dumped resulted in fluctuations in the cash flow of a mining project. The main goal of the long-term production planning is to determine strategies to implement the cutoff grade and short-term production planning. One of the most important aspects of mine design is to determine the optimum cutoff grade. The optimum cutoff grade leads to maximize the profit or the Net Present Value (NPV). Maximizing of NPV is a non-liner programing problem that has been considered in the recent decades. The main factors involved in the Lane algorithm are the capacities of each part of the mine (e.g. extraction capacity of mine, refinery plant, and market), time value of currency and distribution grad of deposit. Since Lane algorithm calculation steps are very time consuming, In this study a novel technique namely Imperialism Competitive Algorithm (ICA) is used to determine the optimum cut-off grade. The results show that optimum cut-off grade obtained by ICA is more accurate and faster than other simulation algorithms. In this paper a novel optimization algorithm based on imperialist competitive algorithm (ICA) is used to determine the optimum cut-off grade in the open-pit mines.Introduction: One of the important aspects of open-pit mine design is determination of cutoff grade, by definition cutoff grade is the grade at which the mineral reserve ca no longer be mined and processed at profit. A cutoff grade is used to assign the destination of material exploited from the mine. This destinations are: (1) to mill, (2) to the waste dump and (3) to the stockpiles. In this paper, determining the optimal cutoff grade of ore to maximize the NPV due to mining limitations, concentration and refining is described by using ICA algorithm.Methodology and Approaches: The ICA algorithm starts with an initial population. Each population in ICA is called country. Countries are divided in two groups: imperialists and colonies. In this algorithm the more powerful imperialist, have the more colonies. When the competition starts, imperialists attempt to achieve more colonies and the colonies start to move toward their imperialists. So during the competition the powerful imperialists will be improved and the weak ones will be collapsed. At the end just one imperialist will remain. In this stage the position of imperialist and its colonies will be the same. In this paper the cutoff grade of hypothetical deposit is calculated using ICA algorithm. This algorithm has 40 country, 6 imperialist and 34 colony. Finally the results is validated by dichotomous method.Results and Conclusions: One of the important parameters of open-pit mine design is determination of cutoff grade. In this paper imperialist competitive algorithm is used to optimize the cutoff grade. Since the roulette wheel mechanism is not used In the ICA algorithm and only a probability density function (PDF) is needed to reach the answer, the ICA algorithm converges faster and better to the optimum point compare with other algorithms.

Summary: This study has been performed with the aim of investigation of dynamic loading effect on permeability of rock mass. The method is 2D numerical modeling that because of discontinuous nature of rock mass and also existence of fracture networks in it, the modeling has been carried out by Discrete Fracture Network-Discrete Element Method (DFN-DEM) conflation approach. Results show that dynamic loading changed the transmissivity of fractures and consequently increased the permeability of fractured rock mass.Introduction: Dynamic loading is a phenomenon that may be applied to rock mass in nature and even leads to changes in some of its geo-mechanical properties such as permeability. The variation in the amount of fluid flow from which the predicted value in a sensitive project such as underground power stations, hydrocarbon fluid flow in its reservoirs and repositories of buried of nuclear waste can cause damages and demolitions. Hence, investigation of dynamic loading effects on the permeability of rock mass is important. In previous studies, some research has been accomplished in the field of rock mass hydromechanics and interaction between static stress and fluid flow in rock mass. However, the lack of evaluation of stress form (static or dynamic) on permeability of rock mass has been felt.Methodology and Approaches: In this study hydro-mechanical numerical modeling has been carried out under static and dynamic stress conditions. All of geometrical and mechanical properties of the models have been for Sellafield site in Cambria, England. As previously mentioned, modeling has been performed by DFN-DEM conflation approach using UDEC. In order to realize results of the method, data from a real earthquake have been utilized as a dynamic boundary conditions. Modeling in this study has been conducted in two groups. Group 1 contains models which have been placed under fluid flow without dynamic loading (in static conditions). In the group 2, the same models have been put under dynamic loading and then under fluid flow conditions.Results and Conclusions: The results show that in contrary with the previous consideration, at least dynamic loading changes the transmissivity of fractures and therefore violates the permeability of fractured rock masses. Despite the fact that in our case study, fracture stiffness is relatively high, calculated permeability of rock mass is greater by 26% at dynamic loading compared with the static loading condition. The major reason is that dynamic loading has caused successive moving the blocks and possible changes in their positions relative to the previous state.