Int. Journal of Mining & Geo-EngineeringInt. Journal of Mining & Geo-Engineering
http://ijmge.ut.ac.ir/
Tue, 26 Sep 2017 11:54:48 +0100FeedCreatorInt. Journal of Mining & Geo-Engineering
http://ijmge.ut.ac.ir/
Feed provided by Int. Journal of Mining & Geo-Engineering. Click to visit.Determination of the height of destressed zone above the mined panel: An ANN model
http://ijmge.ut.ac.ir/article_62147_8211.html
The paper describes an artificial neural network (ANN) model to predict the height of destressed zone (HDZ) which is taken as equivalent to the combined height of caved and fractured zones above the mined panel in longwall mining. For this, the suitable datasets have been collected from the literatures and prepared for modeling. The data were used to construct a multilayer perceptron (MLP) network to approximate the unknown nonlinear relationship between the input parameters and HDZ. The MLP proposed model predicted values in enough agreements with the measured ones in a satisfactory correlation, in which, a high conformity (R2=0.989) was observed. To approve the capability of proposed ANN model, the obtained results are compared to the results of the conventional regression analysis (CRA) method. The calculated performance evaluation indices show the higher level of accuracy of the proposed ANN model compared to CRA. For further evaluation, the ANN model results are compared with the results of available models and in-situ measurements reported in literatures. Comparative results present a logical agreement between ANN model and available methods. Obtained results remark that the proposed ANN model is a suitable tool in HDZ estimation. At the end of modeling, the parametric study shows that the most effective parameter is unit weight whereas elastic modulus is the least effective parameter on the HDZ in this study.Wed, 31 May 2017 19:30:00 +0100Combined application of computational fluid dynamics (CFD) and design of experiments (DOE) to ...
http://ijmge.ut.ac.ir/article_62148_8211.html
Combining the computational fluid dynamics (CFD) and the design of experiments (DOE) methods, as a mixed approach in modeling was proposed so that to simultaneously benefit from the advantages of both modeling methods. The presented method was validated using a coal hydraulic classifier in an industrial scale. Effects of operating parameters including feed flow rate, solid content and baffle length, were evaluated on classifier overflow velocity and cut-size as the process responses. The evaluation sequence was as follows: the variation levels of parameters was first evaluated using industrial measurement, and then a suitable experimental design was constructed and the DOE matrix was translated to CFD input. Afterwards, the overflow velocity values were predicted by CFD and cut-size values were determined using industrial and CFD results. Overflow velocity and cut-size were statistically analyzed to develop prediction models for DOE responses; and finally, the main and the interaction effects were interpreted with respect to DOE and CFD results. Statistical effect plots along with CFD fluid flow patterns showed the type and the magnitude of operating parameters effects on the classifier performance and visualized the mechanism by which those effects occurred. The suggested modeling method seems to be a useful approach for better understanding the real operational phenomena within the fluid-base separation devices. Furthermore, individual and interaction effects can also be identified and used for interpretation of nonlinear process responses.Wed, 31 May 2017 19:30:00 +0100Prediction of fragmentation due to blasting using mutual information and rock engineering ...
http://ijmge.ut.ac.ir/article_62149_8211.html
One of the key outcomes of blasting in mines is found to be rock fragmentation which profoundly affects downstream expenses. In fact, size prediction of rock fragmentation is the first leap towards the optimization of blasting design parameters. This paper makes an attempt to present a model to predict rock fragmentation using Mutual Information (MI) in Meydook copper mine. Ten parameters are considered to influence fragmentation. On the other hand, Rock Engineering System (RES) is employed for sake of comparison between different methods. To validate the results, six blasting scenarios are selected out and compared with results of both models. The coefficients R2, RMSE and MAE were used in an attempt to assess the performance of presented models. The values of the coefficients R2, RMSE and MAE considering two methods of MI and RES for 30 blasting cycles are calculated as (0.81, 10.7, and 9.02) and (0.75, 11.87, and 9.61), respectively, implying the better capability of MI model to predict fragmentation.Wed, 31 May 2017 19:30:00 +0100Estimation of coal proximate analysis factors and calorific value by multivariable regression ...
http://ijmge.ut.ac.ir/article_62150_8211.html
The proximate analysis is the most common form of coal evaluation and it reveals the quality of a coal sample. It examines four factors including the moisture, ash, volatile matter (VM), and fixed carbon (FC) within the coal sample. Every factor is determined through a distinct experimental procedure under ASTM specified conditions. These determinations are time consuming and require a significant amount of laboratory equipment. The calorific value is one of the most important properties of a solid fuel and its experimental determination requires special instrumentation and highly trained analyst to operate it. This paper develops mathematical and ANFIS models for estimation of two factors of proximate analysis based on the other two factors. Furthermore, the estimation of calorific value of coal samples based on proximate analysis factors is performed using multivariable regression, the Minitab 16 software package, and the ANFIS, Matlab software package. The results indicate that ANFIS is a more powerful tool for estimation of proximate analysis factors and calorific value than multivariable regression method. The following equation estimates the calorific value of coal samples with high precision: Calorific value (btu/lb)= 12204 - 170 Moisture + 46.8 FC - 127 AshWed, 31 May 2017 19:30:00 +0100Experimental and Numerical Investigation of Rock Dynamic Fracture
http://ijmge.ut.ac.ir/article_62151_8211.html
Rapid development of engineering activities expands through a variety of rock engineering processes such as drilling, blasting, mining and mineral processing. These activities require rock dynamic fracture mechanics method to characterize the rock behavior. Dynamic fracture toughness is an important parameter for the analysis of engineering structures under dynamic loading. Several experimental methods are used for determination of dynamic fracture properties of materials. Among them, the Hopkinson pressure bar and the drop weight have been frequently used for rocks. On the other hand, numerical simulations are very useful in dynamic fracture studies. Among vast variety of numerical techniques, the powerful extended finite element method (XFEM) enriches the finite element approximation with appropriate functions extracted from the fracture mechanics solution around a crack-tip. The main advantage of XFEM is its capability in modeling different on a fixed mesh, which can be generated without considering the existence of discontinuities. In this paper, first, the design of a drop weight test setup is presented. Afterwards, the experimental tests on igneous (basalt) and calcareous (limestone) rocks with single-edge-cracked bend specimen are discussed. Then, each experimental test is modeled with the XFEM code. Finally, the obtained experimental and numerical results are compared. The results indicate that the experimentally predicted dynamic fracture toughness has less than 8 percent difference with calculated dynamic fracture toughness from extended ﬁnite element methodWed, 31 May 2017 19:30:00 +0100A genetic algorithm approach for open-pit mine production scheduling
http://ijmge.ut.ac.ir/article_62152_8211.html
In an Open-Pit Production Scheduling (OPPS) problem, the goal is to determine the mining sequence of an orebody as a block model. In this article, linear programing formulation is used to aim this goal. OPPS problem is known as an NP-hard problem, so an exact mathematical model cannot be applied to solve in the real state. Genetic Algorithm (GA) is a well-known member of evolutionary algorithms that widely are utilized to solve NP-hard problems. Herein, GA is implemented in a hypothetical Two-Dimensional (2D) copper orebody model. The orebody is featured as two-dimensional (2D) array of blocks. Likewise, counterpart 2D GA array was used to represent the OPPS problem’s solution space. Thereupon, the fitness function is defined according to the OPPS problem’s objective function to assess the solution domain. Also, new normalization method was used for the handling of block sequencing constraint. A numerical study is performed to compare the solutions of the exact and GA-based methods. It is shown that the gap between GA and the optimal solution by the exact method is less than % 5; hereupon GA is found to be efficiently in solving OPPS problem.Wed, 31 May 2017 19:30:00 +0100Numerical Analysis of the Primer Location Effect on Ground Vibration Caused by Blasting
http://ijmge.ut.ac.ir/article_62153_8211.html
Ground vibration is one of the undesirable results of blasting operations. Different methods have been proposed to predict and control ground vibration that is caused by blasting. These methods can be classified as laboratory studies, fieldwork and numerical modeling. Among these methods, numerical modeling is the one which saves time and cuts costs since it takes into account the basic principles of mechanics and provides step by step time-domain solutions. In order to use numerical analysis in predicting the results of blasting operations, the accuracy of the output must be verified through field test. In this study, ground vibration caused by blasting in a field operation in Miduk Copper Mine was recorded using 3-components seismometers of the Vibracord seismograph and analyzed by Vibration-Meter software. Propagation of the waves caused by blasting in the mine slope was modeled using discrete element logic in the UDEC numerical software and compared to the results of the field test. Having tested the accuracy of the results obtained, the effect of primer location and the direction of detonation propagation in the blast hole on the rate of ground vibration caused by blasting was investigated. The results show that by changing primer location from the bottom of the hole to its top, the rate of ground vibration caused by blasting increases.Wed, 31 May 2017 19:30:00 +0100A Numerical Analysis on the Performance of Counterweight Balance on the Stability of Undercut Slopes
http://ijmge.ut.ac.ir/article_62154_8211.html
One of the important parameters in undercut slopes design is the determination of the maximum stable undercut span. The maximum stable undercut span is a function of slope geometry, the strength parameters of the slope material, condition of discontinuities, underground water condition, etc. However, the desired production capacity and therefore the size of excavating equipment will sometimes ask for a wider undercut span. The influence of arching phenomenon in geo-material on the stability of undercut slopes is investigated earlier. It is believed that due to arching effect, some load transfer from the undercut area into stationary remaining side toes leads to a more stable slope. However, the transferred load may result in ploughing failure of side toes. One technique for preventing the ploughing failure is the use of counterweight balance on side toes. In this study, the influence of counterweight size on the stability of the undercut slopes was investigated through a series of numerical model tests using FLAC3D software. It was concluded that there is a meaningful relationship between the counterweight balance size and the maximum stable undercut span where increasing a counterweight size results in a wider stable span. Finally, the numerical results were compared with pre-conducted physical modeling test and a nonlinear relationship was proposed between the counterweight size and the maximum stable undercut span.Wed, 31 May 2017 19:30:00 +0100Prediction of structural forces of segmental tunnel lining using FEM based artificial neural network
http://ijmge.ut.ac.ir/article_62155_8211.html
To judge about the performance of designed support system for tunnels, structural forces i.e. peak values of axial and shear forces and moments are critical parameters. So in this study, at first a complete database using finite element method was prepared. Then, a model of artificial neural network (ANN) using multi-layer perceptron was developed to estimate lining structural forces. Sensitivity analysis showed that among input variables, the cover of the tunnel is most influencing variable. To prove the efficiency of developed ANN model, coefficient of efficiency (CE), coefficient of correlation (R2), variance account for (VAF), and root mean square error (RMSE) calculated. Obtained results demonstrated a promising precision and high efficiency of the presented ANN method to estimate the structural forces of tunnel lining composed from concrete segments instead of alternative costly and tedious solutions.Wed, 31 May 2017 19:30:00 +0100Numerical probabilistic analysis for slope stability in fractured rock masses using DFN-DEM approach
http://ijmge.ut.ac.ir/article_62156_8211.html
Due to existence of uncertainties in input geometrical properties of fractures, there is not any unique solution for assessing the stability of slopes in jointed rock masses. Therefore, the necessity of applying probabilistic analysis in these cases is inevitable. In this study a probabilistic analysis procedure together with relevant algorithms are developed using Discrete Fracture Network-Distinct Element Method (DFN-DEM) approach. In the right abutment of Karun 4 dam and downstream of the dam body, five joint sets and one major joint have been identified. According to the geometrical properties of fractures in Karun river valley, instability situations are probable in this abutment. In order to evaluate the stability of the rock slope, different combinations of joint set geometrical parameters are selected, and a series of numerical DEM simulations are performed on generated and validated DFN models in DFN-DEM approach to measure minimum required support patterns in dry and saturated conditions. Results indicate that the distribution of required bolt length is well fitted with a lognormal distribution in both circumstances. In dry conditions, the calculated mean value is 1125.3 m, and more than 80 percent of models need only 1614.99 m of bolts which is a bolt pattern with 2 m spacing and 12 m length. However, as for the slopes with saturated condition, the calculated mean value is 1821.8 m, and more than 80 percent of models need only 2653.49 m of bolts which is equivalent to a bolt pattern with 15 m length and 1.5 m spacing. Comparison between obtained results with numerical and empirical method show that investigation of a slope stability with different DFN realizations which conducted in different block patterns is more efficient than the empirical methods.Wed, 31 May 2017 19:30:00 +0100The role of catalyst in the passivation of chalcopyrite during leaching
http://ijmge.ut.ac.ir/article_62157_8211.html
In this work, we present as investigation of chalcopyrite leaching under different leach conditions for how liquidation and surface of chalcopyrite study using Scanning Electron Microscopy (SEM) to determine the composition of the passivation layer in the surface of chalcopyrite. The study of chalcopyrite dissolution were in H2SO4 solution systems at pH of 1.2, with 5% chalcopyrite concentrate in redox potential of 460 mV at 90°C. The tests were directed to study on the leaching of chalcopyrite in ferric sulfate solution to extract copper with adding pyrite, silver and silver coated pyrite. In these approaches, achieved recoveries were different. The results showed that, in the present of pyrite, the presence of the elemental sulfur layer formed around the chalcopyrite particles which hindered the complete dissolution of copper in chalcopyrite. Also, in the presence of silver, no commercial process has been developed which successfully as a catalyst to recover copper from chalcopyrite. Because, the precipitation of argentojarosite, which forms during the leaching process, limits the availability of silver ion in solution which may act as a catalyst. But syndicate of silver and pyrite to form of silver coated pyrite, causes dissolution increase. However, in the presence of the pyrite coated by silver, leaching was very rapid for the duration of the test, and complete copper extraction was achieved within 10 hours.Wed, 31 May 2017 19:30:00 +0100An Image Analysis-Based Methodology for Chromite Exploration through Opto-Geometric Parameters; ...
http://ijmge.ut.ac.ir/article_62158_8211.html
Traditional methods of chromite exploration are mostly based on geophysical techniques and drilling operations. They are expensive and time-consuming. Furthermore, they suffer from several shortcomings such as lack of sufficient geophysical density contrast. In order to overcome these drawbacks, the current research work is carried out to introduce a novel, automatic and opto-geometric image analysis (OGIA) technique for extracting the structural properties of chromite minerals using polished thin sections prepared from outcrops. Several images are taken from polished thick sections through a reflected-light microscope equipped with a digital camera. The images are processed in filtering and segmentation steps to extract the worthwhile information of chromite minerals. The directional density of chromite minerals, as a textural property, is studied in different inclinations, and the main trend of chromite growth is identified. Microscopic inclination of chromite veins can be generalized for exploring the macroscopic layers of chromite buried under either the surface quaternary alluvium or overburden rocks. The performance of the OGIA methodology is tested in a real case study, where several exploratory boreholes are drilled. The results obtained show that the microscopic investigation outlines through image analysis are in good agreement with the results obtained from interpretation of boreholes. The OGIA method represents a reliable map of the absence or existence of chromite ore deposits in different horizontal surfaces. Directing the exploration investigations toward more susceptible zones (potentials) and preventing from wasting time and money are the major contributions of the OGIA methodology. It leads to make an optimal managerial and economical decision.Wed, 31 May 2017 19:30:00 +0100