جستجوی مقالات مرتبط با کلیدواژه « d modeling » در نشریات گروه « مهندسی معدن »

In this research, the importance of the parameters affecting the oil wellbore stability has been investigated. This study has been performed by the finite element method and modeling in the Phase 2 software. “Maximum total displacement” is considered as the representative of wellbore stability. The impact of each parameter on the wellbore stability was investigated by changing the values of the parameters. Finally, pore pressure and drilling mud pressure were recognized as the most important parameters affecting the wellbore stability.

The main purpose of this research is to analyze and model the audio-magnetotelluric (AMT) data to study the regional structure and deep groundwater of the Sena- the Shonbe aquifer system in central Zagros. We used challenging methods to determine the dimensionality of the regional structure, evaluate the degree of inherent distortion caused by small-scale, near-surface inhomogeneities, quantify these effects and remove them from MT measurements, and retrieve the main features of the regional geoelectric structure (e.g., its strike direction). Data were collected at 19 stations along the profile in the southeast of the folded belt (SFB) of the Zagros folded belt. First, the regional subsurface structure was classified using impedance and MT tensors rotational invariants (Bahr and WAL invariants). Then, the phase tensor method was used to estimate the strike direction of the regional geo-electric structure. The results of Bahr and WAL invariants confirm regional 1D and 2D structures with local galvanic distortion at most periods. Rotating the data into the strike direction of the regional structure, isotropic two-dimensional inversions of the different polarizations of the impedance data and tipper vectors were performed. The computer program used for this purpose uses the nonlinear conjugate gradient (NLCG) algorithm to minimize the cost function, which consists of data misfit and model roughness. Several numerical tests were performed to determine the optimal values of the parameters regulating this algorithm: τ, α, β, and H/V ratio. Finally, interpretations related to the resulting electrical resistivity cross-section are provided.

Short term mine scheduling aims to provide a constant amount of material to the milling facility. Among the available approaches, mathematical modeling is reliable in determining an optimum solution. Cut and fill mining is conducted in mineral reserves with weak surroundings. In this paper, a new mathematical model is introduced to production scheduling of drift and fill mining method while the special constraints of cut and fill mining is considered. The model is capable to consider mining operation in several levels. The model is applied for stope sequencing in Anguran mining project. The data from the +2721, +2733 and +2737 levels are used for production scheduling and stope sequencing. The Anguran underground project is a cut and fill mining project. In this mine the levels are separated into 2 northern and southern panels. The results show that simultaneous mining of +2721 and +2737 levels is capable of reaching the predetermined production level with a maximum deviation of 2.4%.

Pipe jacking is a scientific, economic and environmental solution for the construction of underground facilities that performs a key role in the implementation of projects. In this method, simultaneously with the excavation operation by the shield, the pipes are jacked using hydraulic jacks. Ground deformation during pipe jacking operations is one of the main challenges that its analysis is necessary for safety purposes and project design. Several factors affect the pattern of ground deformation during pipe jacking operations. The effect of each parameter and their sensitivity must be determined so that the ground deformation can be controlled with proper design. The study of displacement patterns in the field of layers based on numerical simulation of finite elements and finally, the analysis of their sensitivity is a subject that has been the subject of limited studies in this field. In this study, modeling details such as a conical excavation shield, increased gradient of grout injection pressure and excavation plate pressure have been considered to be close to the real state. The displacement values at the ground surface and the crown of the pipeline are analyzed. In this study, numerical simulation has been performed using the PLAXIS finite element numerical software and considering a case study. The results of numerical modeling were calibrated with the results obtained from field and theoretical studies, and then the effect of each parameter on the pattern of ground deformation as well as estimating the quantity of uplifts and their exact location were investigated. In the next step, the relationship between each parameter and ground subsidence was estimated and finally, the effect of each of the different factors was measured using sensitivity analysis and the sensitivity index of each was determined. The results show that the most sensitive factor to subsidence is the diameter of the excavated space and the least important factor is the face excavation pressure. Most subsidence occurs at the end of the excavation shield due to the conical nature of the shield and the stress relaxation. Finally, according to the results, it was determined that the relationship between the internal friction angle and the elastic modulus with the ground surface settlement is linear but indirect. The relationships of other parameters were also evaluated nonlinearly.

Pile movement is one of the rock blasting outcomes that, considering the type of haulage machines, has a direct effect on the efficiency of the loading process. In this study, using UDEC discrete element software, the pile movement of fragmented material caused by the blasting operation is modeled. Since UDEC is not capable of modeling the whole process of rock blasting, to accurately model the pile movement of fragmented material, the damping coefficients must be changed in a way to allow the move freely out of the split blocks after the blast, be modeled. The numerical modeling results show that implementing a negative exponential function with three (the initial, threshold, and power) eigenvalues, as the fish-function to the damping coefficient, can model the results pile movement. With the help of this damping function, three blasting blocks with one and two rows of blast holes were modeled. The results of these modeling show that the pile movement for the two rows of blast holes depends on the inter-row delay time, and for the delay times of 17 ms and 50 ms, the maximum horizontal movement of the pile was 30 m and 55 m, respectively. These values show good agreement with the values measured in an actual blast operation. The results of this study show that by changing the negative exponential function eigenvalues defined for damping, the velocity of the fragmented blocks, the displacement, and the geometry of the pile, could be modeled. This shows the capability of the discrete element method in the modeling of the results of rock blasting.

With the advent of big data in geosciences, exploration studies have entered new dimensions. Big data means high resolution image information. Since these data in geosciences have a very large volume and variety, it is necessary to use big data analysis approaches in this field. In this study, the application of support vector machine in machine vision in the field of mineral potential exploration is investigated. In recent years, image classification has attracted a lot of attention in machine vision, whose processes include pre-processing and segmentation, feature extraction and related class identification. In this study, geological maps and remote sensing images are used to model the exploration of minerals potentials, and Alexnet architecture is used to automatically extract features, and field information is used to learn the algorithm. In the next step, support vector machine is used for modeling in order to identify structure factors in the occurrence probability of minerals potentials. Algorithms and evaluation indicators are programmed in MATLAB environment at each stage. The accuracy obtained using this method is 71% on the test data. According to the previous study conducted by the authors in identifying mineralization structures, the average accuracy of image data classification using convolutional neural network algorithms is 65%, the spectral angle mapper method in identifying alteration zones is 70% and applying filters in identifying faults is 28%. As can be seen, the method used in this research is highly accurate. Its advantages include reducing costs and speeding up the decision-making processes.

Due to the lack of a suitable model for estimating tunnel face pressure in the serviceability limit state, a comprehensive research study is conducted for Tehran metro tunnels. In this context, by using numerical modeling with Plaxis 3D V20 software, as well as by performing validation and sensitivity analysis, and by considering the parameters affecting the surface settlement in the area of Tehran soils, a new method for estimating tunnel face pressure is provided in the serviceability limit state. This method is based on the statistical analysis of the results of 80 numerical models whose range of parameter values is adjusted according to the range of Tehran soil parameters.

Methodology and Approaches:

In this research study, Plaxis 3D V20 software is used for numerical modeling. In the modeling stages, in order to make the modeling results closer to reality, the step-by-step construction process of tunnel excavation has been followed. In order to validate and check the correctness of the 3D numerical modeling, the data of the Southern Extension Tehran Metro Line 6, as well as the results of instrumentation and monitoring, have been used. In the end, multiple regression analysis has been used to investigate the combined effect of effective parameters on the tunnel face stability number using the results of numerical modeling.

In the validation of numerical modeling, in geological sections whose settlement is less than 8 mm, modeling in an undrained state provides more consistent results with the actual settlement information. In the geological sections whose settlement is more than 8 mm, modeling in a drained state provides more consistent results with the actual settlement information. A new empirical formula for the estimation of the tunnel face stability number has been obtained using multiple regression methods in the drained state. The determination coefficient of this formula is 68%. Also, three formulas for estimating the stability number were obtained using simple regression formulas.

Tunneling in urban areas by passing underneath several buildings causes subsidence due to stress relief and development of elastic and plastic deformations. If these subsidences are not controlled, the structures on the ground will be seriously damaged. Nowadays, several methods are used for tunnel analysis and design and for urban tunnels, which excavated in shallow and soft grounds, the best way is using numerical methods. Choosing the Appropriate behavioral model is one of the most basic steps in numerical analysis. tunnel excavation frequently uses the Mohr–Coulomb behavior model in numerical models.The Mohr-Coulomb elastic-plastic model is one of the most widely used models, used in cases evaluating the hardness of materials, independent of the surface tension. If the Mohr-Coulomb used for modeling of tunnel where in depth tunneling excavation is involved and where an increase in maximum ground surface settlement and decrease in the reliability of stability of tunnels can be seen, which may not be appropriate in some conditions. The more appropriate model should be used to solve this problem, one that can model the hardness of materials based on changes in the level of stress.In this study, the effect of different soil parameters on the ground surface settlement of Qom metro line A in Hardening Soil, Mohr–Coulomb and Drager Prager behavior models was investigated using the finite difference method. First, modeling of ground surface settlement was performed and the analysis results were compared with instrumentation data. Then, the effect of modulus of elasticity, friction angle, cohesion, Poisson's ratio and specific gravity parameters in different behavior models was investigated. The results of this research indicated that the Hardening Soil behavior model and the Drager Prager behavior model have the most and the least changes from the changes of soil parameters of Qom metro line A, respectively.

Despite the development of numerous excavation methods and reinforcement of tunnels, finding a proper method for stabilization of underground structures is a challenging task. The use of pre-reinforcement systems is an appropriate method to improve the status of the ground. In this study, the performance of umbrella system in Alborz tunnel in north of Iran has been investigated. Rock mechanics studies of tunnel running area have shown that parts of this tunnel have unstable capacity due to being located in weak zones. Therefore, the tunneling operation running is not possible in these areas. On this basis, umbrella pre-reinforcement system that can be used for loose and running ground are modeled numerically by Flac3D software. In this research, in addition to investigating the performance of umbrella system, the effect of geometrical parameters such as the angle of placement of pipes relative to the horizon and the distance between the umbrella system pipes was investigated. The criterion of investigating is the displacement occurred at the crown of the tunnel. The results of this study indicate that increasing the angle and decreasing the distance between pipes, cause an increase in stability and by using umbrella system, the vertical displacement of crown of the tunnel has decreased by 70 %.

Due to construction of high-rise buildings and construction of underpass intersections and also due acceleration of construction of high-rise buildings in most metropolitan areas, deep and shallow excavations always bring advantages and disadvantages for engineers. During the construction of underpasses that are located below the groundwater level, no problem can disrupt the project development process as much as the presence of water problem ،due to this problem in the Baghodrat martyr underpass project of Kerman city to reduce groundwater ،different methods were studied. Eventually Valid scientific documents, the use of pumping wells and guidance to the intended location for drainage and stabilization of the well by nailing were confirmed. In this research, first numerical modeling Baghodrat martyr underpass of Kerman city using finite element method using Plaxis2D software and by changing the mechanical properties soil including internal friction angle, adhesion and permeability of soil as well as outlet pumping discharge, the maximum vertical subsidence The edge of the pit was calculated and the necessary analysis was performed in this regard. The results showed that increasing the angle internal friction and adhesion and soil permeability coefficient reduced sedimentation and increasing pumping discharge increased soil sedimentation. Then, using multilayer prosthetic artificial neural network in MATLAB software and Plexis software data as network entrance, the values of ambient subsidence around the pit in other cases have been predicted. Finally, an artificial neural network with a correlation coefficient of 0.982 is obtained, which indicates the accuracy and power of accurate prediction of real values.