JOURNAL OF ANALYTICAL AND NUMERICAL METHODS IN MINING ENGINEERING
Year:2017 | Volume:6 | Issue:12 |Papers Count:9

Summary: Ventilation is one of the most important safety issues in mining operations. Proper analysis of mine ventilation network requires a detailed understanding of air movement in different parts of the mine. Ventilation analysis in medium and large underground mines is complicated and requires numerical modellings to be done. Among the approximation methods of network analysis is the node – loop method which is also known as linear theory method. In Hardy - cross and Newton-Raphson methods, initial guesses are used based on the continuity equations of nodes that are difficult for the large networks and time consuming. The advantage of the node-loop method is that it doesn't need to consider the initial guessing for node equations. Another advantage of this method is the higher speed of convergence for second-order equations. Initially, this method was used in electricity and water distribution networks, but it seldom has been used in mine ventilation network. In this paper, the fundamentals of ventilation network equations and node - loop method are explained. Then the use of this method for solving the equations in mine ventilation is discussed. Network equations are introduced by matrix forms based on branches flow rates. The governing equations for the network and the method for linearization are introduced, followed by a numerical example of mine ventilation network. Finally, Pabdana mine ventilation network has been analyzed by the node-loop method. In this case study, air distribution was calculated in different parts of the mine with good convergence not using initial guess.Introduction: Ventilation is one of the most important safety issues in mining operations. Proper analysis of mine ventilation network requires a detailed understanding of air movement in different parts of the mine. Ventilation analysis in medium and large underground mines is complicated and requires application of numerical methods.Methodology and Approaches: The node-loop method for ventilation network is used in this paper. The practical application of this method is for modeling and analysis of mine ventilation networks. The governing equations and the linearization method are introduced. The advantage of the node-loop method is that there will be no initial guessing for implementing solution. The structured matrixes used are made so that to fit comprehensive ventilation conditions in mines, which includes simultaneous application of fans and natural ventilation.Results and Conclusions: The node-loop method is shown as an alternative method for mine ventilation networks. The use of this method for solving the equations in mine ventilation is discussed. Network equations are introduced by matrix forms based on branches flow rates. A numerical example of mine ventilation network is followed to better introduce the method. It has also been shown that in this method the speed of convergence is higher for the second-order equations. Finally, Pabdana mine ventilation network has been analyzed by the node-loop method. In this case study, air distribution was calculated in different parts of the mine with good convergence. The operational point of fans is also obtained. The method can be introduced for mine ventilation design and analysis.

Summary: One of the most important methods in unsupervised datamining is clustering  that when applied on variables leads to dimension reduction. Among all of them, fuzzy clustering methods are preferred because of special features and better flexibility in partitioning groups.  In this study, FANNY algorithm proposed by Kauffmann and Rousseuw has been applied in variable clustering of the  geochemical stream sediments that have a compositional nature. Referring to the extensive recent researches and novel methods presented in opening  compositional data, another definition of distance is needed for them to be transformed isometrically to the euclidean space to be interpretable with classical operations. In this case study after preparation of geochemical stream sediments data of Anar region in Kerman, first the exploratory dendrogram of the simplex space was plotted and 4 clusters were obtained. Then using fanny algorithm, clr-transformed variables were clustered. It showed an acceptable conformity with the dendrogram results. In case of determining the balances of SBP manually instead of default and with a prior knowledge, the results of exploratory dendrogram would be more precise.Introduction: Geochemical exploration based on stream sediment analysis, is one of the most important methods in assessing mineral potentials in prospecting brownfield areas. Different statistical methods have been developed to identify the pattern of groups of associated geochemical elements in the last decades. In this research, stream sediments data clustering of Anar exploratory region have been analyzed with a particular perspective of the closed nature of geochemical datasets using two known methods, fuzzy clustering and exploratory dendrogram.Methodology and Approaches: First, using R software compositions-package, exploratory dendrogram of compositional data was calculated and plotted based on ward criterion and default sequential binary partition balances in simplex space. Due to applying this method, 4 clusters were detected. Then by applying  fanny algorithm (cluster package) –one of the most flexible ones in fuzzy clusterings –on clr- transformed data, 4 clusters with the best silhouette were determined. The fuzzification degree was selected in a way that would be near to crisper methods like dendrogram in order to compare the results.Results and Conclusions: Although different methods applied on transformed compositional data, their similar results showed very good conformity with lithology and geological structures. It presented a good separation in simplex space. If the balances in SBP are to be defined manually, the reduced dimensions of the variables would be more informative.

On The Sechahoon iron ore mine located in Yazd Province, since most of iron ore deposit is placed at the bottom of water table, a complete study about the hydrogeology around open pit of mine is necessary. In this regards, by using surface geological data and the existing sections, and use information from boreholes drilled in the area build a three-dimensional geological model and compared with the water table and geoelectric data were examined. Survey data Lugeon and Lufran tests to determine the hydrodynamic coefficients of the layers, survey data on precipitation and evaporation, check fractures and faults in the flow channels in the formation of hard preparation of data for entry into the numerical model. Geology modeling output entered to the numerical model as aquifer geometry. Due to inside the mining area in the watershed Sechahoon and determination of the amount of water entering to the mine was initially modeled catchment area at steady state. The amount of water input and output of the mine area was determined using the catchment model. These models were made at steady state by Feflow 6.2. Due to the complexity of a heterogeneous environment, the results of numerical modeling of catchment at steady state with 61% correlation between model and Measuring water table is acceptable. Water inflow in the open pit mining is the southeast and the northwest part of it is outflow. Given the general trend north-south fault zone, the rate of change of the water table in the extreme east-west and north-south direction is lower. Also, considering the highest amount of flux is in line with faults and fractures of region, the water table isoline in many parts of model are closed.

Summary: In this research, stability analysis and probability assessment of the further failure for Angooran lead and zinc mine have been investigated. To investigate its geomechanical properties precisely, main joints and available faults were appraised and some samples of the mine limestone zone were prepared to determine strength properties of rocks using laboratory tests. Then, the 3DEC code was used to construct a three dimensional model. According to the initial displacements from the software and geomechanical properties of the eastern wall and its concave shape, this wall was supposed to be stable. Further analyses were focused on the western wall. For stability analysis of the western wall, the model was constructed based on different cohesions and internal friction angles. It was observed that the magnitudes of displacements were higher than in the eastern wall. So, statistical analysis was performed on the toe of the wall and the probability of the failure calculated to 35.2 percent, according to the obtained displacements.Introduction: Slope stability is one of the major and determiner parameters in the economy and safety of open pit mines. Failure and consequently rupture of the slope caused no compensable economic and humanity losses. So, probability assessment of the further failure for presentation of damages and additional costs is of prime importance. In this research, stability analysis and probability assessment of the further failure for Angooran lead and zinc mine have been investigated.Methodology and Approaches: To investigate geomechanical properties precisely, main joints and available faults were appraised and some samples of the mine limestone zone were prepared to determine strength properties of rocks using laboratory tests. Then, the 3DEC code was used to construct a three dimensional model. According to the initial displacements from the software and geomechanical properties of the eastern wall and its concave shape, this wall was supposed to be stable. Further analyses were focused on the western wall. For stability analysis of the western wall, the model was constructed based on different cohesions and internal friction angles.Results and Conclusions: In this research, field and laboratory studies were carried out in order to achieve accurate data of Angooran lead and zinc open pit mine. According to the obtained displacements of the model, probability of heavy failure was evaluated. ...

Summary: Modelling and simulation have increased in the study of rock engineering in the past decades. Numerical simulation is an important tool for analysis that is impossible to do in the laboratory. The main reasons for using numerical modeling in laser drilling which can be mentioned are lack of access to high confining pressure in the existing laboratory condition, increase in the cost of drilling in large diameter, differentiation mechanical and thermal stresses and strain caused by the laser in the laboratory, as well as important secondary effects in laser drilling on rock. In this study, a Finite Element Method (FEM) is used for understanding the thermal and mechanical stresses caused by the ND: YAG laser drilling in the reservoir rocks. For this purpose, ABAQUS code was employed to analyse the thermal and mechanical stresses. A numerical model of a core rock was simulated and thermal properties of a reservoir rock such as thermal conductivity, heat capacity and density were imported into the code. By entering drilling rate to the model, tests carried out in the lab were simulated and after conformity with them, high confining pressures were imposed.Introduction: Laser perforating is a new scientific approach to the generation of uniform holes in oil and gas reservoir wells at a selected pitch to improve the permeability of rocks. Thermal stress generated by differential thermal expansion of minerals and high-temperature gradient, breaks the bonds between the grains. In this range of temperature, physical and chemical changes occur that are associated with the process of spallation. Hence, Laser rack spallation is a complicated phenomenon depending on many factors. Using experimental studies to comprehend this phenomenon is merely expensive and time-consuming. Since there are not enough techniques to appraise some of the factors, they should be studied in the laboratory. On the other hand, numerical modelling provides simulative action of the factors which are difficult to be considered by experimental research. Many researchers have been examined the laser cutting process. In previous studies, researchers focused mainly on some factors to improve the cutting quality and assess the thermal stress levels around the cutting section. However, these studies were limited mainly laser cutting of rock and has not been examined the thermal and mechanical stress analysis in detail.Methodology and Approaches: The finite element model has been used to simulate the thermal and mechanical stresses induced by laser drilling ND: YAG. For this investigation, some samples have been taken from a hydrocarbon reservoir in Ahvaz. For this purpose, ABAQUS software was used and thermal properties of reservoir rocks, such as thermal conductivity, density and heat capacity were considered.Results and Conclusions: Results of the numerical study show that the model has good agreement with the lab tests. Around the drilled holes, thermal stress induced by the laser is lower than the mechanical stress caused by confining pressure. And the distribution of the stress concentration has a high correlation with the amount of confining pressure.

Knowing the amount of existing water in clay-like material not only provides the means to predict the drying time more accurately, but also can help in better process control reducing time and energy. In addition, it is possible to predict occurrence of defects such as crack and distortion.The current research; employs infrared imaging technology to record temperature changes during a controlled drying process of several clay-like material samples. Transient heat transfer and equations of semi-finite object are used to study the moisture and its changes during drying process. Comparing the experimental data with analytical values shows that the semi-finite model and thermal imaging can be used to evaluate the moisture content of clay-like objects. Thermography; being a non-contact digital method is significantly quicker than traditional mechanical methods, hence; it can be employed to visualize the distribution of moisture on the surface of the objects without mechanical intervention.

Summary: Anisotropy is an important feature of sedimentary and metamorphic rocks. This character affects opening stability and must be considered in design. So many laboratory tests are done to consider the influence of anisotropy on mechanical behavior and failure strength of such rocks.Introduction: Numerical modeling is an effective tool in design of structures and stability analyses. Because of computational complexity and the difficulty of determining the necessary elastic constants, it is usual for only the simplest form of anisotropy, transverse isotropy, to be used in design analyses. The peak strengths developed by transversely isotropic rocks in triaxial compression vary with the orientation of the plane of isotropy, foliation plane or plane of weakness, with respect to the principal stress directions.Methodology and Approaches: In this study the behavior of a transversely isotropic rock under triaxial loading is considered by using distinct element method due to its potential to modeling failure process of anisotropic materials and because of its ability to monitoring failure of these rocks under uniaxial and triaxial conditions. The bonded-particle discrete element method with embedded smooth joints was applied to model the mechanical behavior of transversely isotropic rock with systematic verifications. Particle Flow Code 2D (PFC2D) developed by Itasca was applied in this study to employ the bonded-particle DEM. The bonded particle model was adopted to construct isotropic rock without weak planes, which was calibrated based on elastic modulus and strengths that have the least effect of weak planes. Then, the smooth joint model was inserted to create the weak cohesive planes to simulate the behavior of the equivalent anisotropic continuum.Results and Conclusions: The results showed that the bonded-particle DEM model with embedded smooth joints was able to simulate the transversely isotropic rock. In this Research, some samples made by PFC were loaded under confining pressure in varying layering angle (0 to 90). Results showed that the distinct element method is able to model transversely isotropy and is in a good accordance with experimental data. Also it’s indicated that the peak strength of transversely isotropic rock is related to angle of anisotropy and its variation versus to layering angle show U-shape curves with unequal shoulder which has a minimum value in 30 degree of layering and a maximum value in zero. Results indicated that increase of confining pressure doesn’t change the failure mode of transversely isotropic rocks, unevenness ratio and depth ration. This study pave the way for further applications, and the bonded-particle DEM model can be further employed effectively in rock engineering applications, particularly in transversely isotropic rock formations.

Summary: There are many factors which affect the interaction between non-level crossing tunnels such as excavation sequence, excavation method, lining thickness, the distance between tunnels, the length of unsupported span, soil properties and etc. The excavation sequence is one of the most important factors which should be determined before construction of their intersections, especially in urban areas as it has many effects on surface subsidence and other negative aspects of tunneling. The main purpose of this study is determining the best excavation sequence for non-level crossing tunnels in urban areas. For this purpose, the intersection between lines 6 and 7 tunnels of Tehran subway has been considered and the best alternative for a sequence of their excavation was determined by 3D numerical models by MIDAS GTS NX, numerical finite element software. Both tunnels have an equal diameter and are excavated by TBM-EPB machines. This software has good capabilities for modeling of mechanized excavation of tunnels. To achieve the above-mentioned objective, three scenarios, and five alternatives were considered and in each scenario, the effect of excavation sequence on the results of the model such as surface subsidence, total displacement, axial and shear forces on lining has been investigated by numerical models. The results show that the best scenario is the excavation of upper/shallow tunnel at least 10 times of diameter earlier than lower/deeper tunnel.Introduction: First of all, assumptions considered are intended. Then, literature was reviewed and the project is introduced precisely. Finally, the 3D model by finite element software was made, and all scenarios and alternatives of excavation sequences were investigated. According to results the best scenario is the excavation of upper/shallow tunnel at least 10 times of diameter earlier than lower/deeper tunnel.Methodology and Approaches: Because there are various factors affecting the interaction of non-level crossing tunnels, so the best method for investigating these, are numerical models. And because the medium that tunnels are constructed in is a continuum, the finite element method for solving the problem is used. And due to 3D nature of the problem, 3D modeling is used.Results and Conclusions: As mentioned before, the best scenario is the excavation of upper/shallow tunnel at least 10 times of diameter earlier than lower/deeper tunnel. Other researchers also believe to the results obtained. So suggestion for feature studies is: the investigation should be focused on only the scenarios that shallower tunnel is excavated first.

Due to technological progress and consequently the development of numerical methods in solving problems, numerical methods have found a special place in various sciences especially rock mechanics. Numerical methods can be used according to the type of medium used as a combination that so-called hybrid methods. According to studies on slope stability analysis, displacement discontinuity method for crack growth and discontinuous deformation analysis method for modeling large displacements as combination was found suitable. Hence first by providing flowchart of how the combination of these two methods, with geometrical modeling using random disks method and infinite joints method in the program coding in the Mathematica environment, to crack growth in the geometrical model created by random discs coded in the Mathematica program deals and finally, stability analysis was conducted in the DDA and UDEC software. It is worth mentioning, the case studies used in this study was tectonic block 4 Choghart and according to the comparison be made can clearly capabilities discontinuous deformation analysis method than the discrete element method in modeling large displacements observed. It is worth mentioning that crack growth creates geometric model is different and follow different results in the slope stability analysis.