نشریه روش های تحلیلی و عددی مهندسی معدن
پیاپی 40 (پاییز 1403)

Correctly predicting the behavior of the ground during tunnel excavation compared to what will happen in reality is a very challenging matter, especially in urban tunnels. On the other hand, the faster this prediction is and without the need to spend more money, the more valuable it will be. In the present study, the goal is to investigate the effectiveness of a hypo-plastic model to predict the results of physical modeling in the laboratory. For this purpose, the behavior of the surrounding environment of a tunnel in sandy soil was simulated using a hypo-plastic behavioral model, and the resistance characteristics of the studied soil were validated based on the triaxial test results. At the same time as simulating the tunnel excavation process, the settlement of the ground surface and stress changes in the soil above the tunnel were measured for different values of soil densities and tunnel depths. The results of this research showed a good agreement with the results of physical and theoretical modeling. Based on the results of this research, the hypo-plastic model can predict the behavior of loose granular soils. Convergence of the tunnel leads to disturbance of the stress field around the tunnel, and due to the phenomenon of soil arching around the tunnel, the stress distribution deviates from the linear state. Under the same conditions, although the loosened zone above the tunnel expands with the increase of the tunnel depth, the settlement of the ground surface decreases.

An authentic understanding of formation pore and fracture pressures is essential to define a safe and optimum mud window in drilling oil and gas wells. This investigation is a challenge in formation pressure studies in the South Azadegan field, which is typically carbonated with very low traces of shale beds, except in the Kazhdumi Formation. The wells drilled in this field hinged on the geological information and pore pressure alterations, can be categorized into three classes; Gachsaran, Pabdeh, and surface formations containing marl. These parameters directly affect the selection of the casing shoe depth and the well schematic. Correspondingly, target reservoir formations, i.e., Sarvak, Kazhdumi, Gadvan, and Fahliyan, and well profiles are other parameters that can classify wells in terms of drilling. It is necessary to analyze and model all upper formation pressures to obtain more precise results to investigate the pore pressure profile in these formations. Effective pressure log data reveals an increasing trend in formation pressure with depth in all wells. Besides, there are a few effective pressure-velocity data pairs in the total data of the Fahliyan Formation of Azadegan wells. With the small number of effective pressure-velocity data pairs in the total data of the Fahliyan Formations of Azadegan wells and the very low correlation coefficient of the Bowers relation for the wells of the Fahliyan Formations, it was necessary to separate this formation into two upper and lower parts. So the modeling has been performed by constructing compressional velocity-effective pressure cubes. This research was based on the data gathered from various drilled wells in this region and the interpretation of seismic data. Also, the effective, pore and formation fracture models have been determined from the integrated geostatistical models validated with the pressure-volume fractal model. The most heightened correlation between the final velocity and effective pressure cubes corresponds to the Ilam with 0.71 and the lower Fahliyan Formations with 0.86, which signifies the model's accuracy with the original data. Based on the final pressure cubes of the formation, the maximum pore pressure of 10,000 psi in the Gadvan to Upper Fahliyan Formations and the maximum fracture pressure of 13,000 psi in the lower Fahliyan to Gotnia Formations have been obtained. In this research, an innovation has been made to study the formation pressures utilizing fractal pressure-volume (P-V) methods. Also, for the construction of the final formation pressure cube model in the entire area of the South Azadegan field, for the first time, the combination of geostatistical methods of sequential Gaussian simulation (SGS) and co-kriging with the acoustic impedance (AI) cube obtained from seismic inversion has been used together. Computation of the Logratio matrix resulting from the fractal pressure-volume model revealed the maximum overall accuracy (OA) in the dominant limestone intervals as 0.74 at the depths of 2000-3000 meters, corresponding to the Sarvak to Asmari Formations. The results exhibit the high correspondence of the pore pressure cube model, obtained by sequential Gaussian simulation (SGS) combined with co-kriging and acoustic impedance inversion...

Concretes frequently contain joints and microcrack fractures, and the failure mechanism of these fractures is highly dependent on the pattern of crack coalescence between pre-existing flaws. Determining the non-persistent joints' failure behavior is an engineering challenge that incorporates several factors, including the ratio of the joint surface to the total shear surface, normal stress, and the mechanical characteristics of the concrete. This paper aims to utilize grey wolf optimizer (GWO) and gene expression programming (GEP) algorithms for the prediction of the crack coalescence stress (CCS). For this purpose, 8 input parameters affecting the CCS including jointing coefficient (JC), normal stress (σn), uniaxial compressive strength (σc), tensile strength (σt), Poisson's ratio (υ), modulus of elasticity (E), cohesion strength (C) and internal friction angle (φ) were selected based on the results of 450 direct shear tests conducted on specimens including 2 sets of non-persistent joints made of gypsum, cement, and water. The GWO and GEP techniques were then implemented. Three performance indicators of determination coefficient (R2), root mean square error (RMSE), and mean absolute error (MAE), were employed for the training and testing phases to evaluate the efficiency of the suggested models. The R2 values for GWO and GEP for the training phase were 0.962 and 0.938, respectively, while for the testing phase were 0.996 and 0.981, indicating that the GWO algorithm is more efficient than GEP. Moreover, the findings reveal that the GWO algorithm exhibits lower RMSE and MAE values in both the training and testing phases compared to the GEP method. However, it can be professed that the two methods used have high reliability and accuracy. Also, based on the GEP method, a formula was derived and presented for prediction of CCS. At last, according to the sensitivity analysis, it was found that the normal stress (σn) and jointing coefficient (Cu) have the greatest and least influence on CCS, respectively...

Blasting operation is one of the most important and costly operations in the mining process. Blasting is the beginning of the rock comminution system in the mine. The dimensions of the blasted product will play a significant role in the ability of stone crushing and grinding, for this reason, to produce a product with suitable dimensions, it is first necessary to obtain sufficient knowledge of the physical, mechanical, and chemical conditions of mineral blocks. In this research, by studying 26 iron ore blocks of the Chogharat mine, after the blasting operation, the physical, mechanical, and chemical characteristics of the ore blocks were taken. In the following, after blasting operation, by taking pictures from surface of the exploded block, an image analysis of the dimensions of blasting product was carried out. In the next step, stone samples were taken from the surface of the fired block to conduct geomechanical and chemical tests. After conducting the tests, the relationship between the physical, chemical, and mechanical characteristics of the tested stones with the dimensions of the Blast products (D50) was investigated. The characteristics examined in this study include uniaxial compressive strength, modulus of elasticity, Poisson's ratio, indirect tensile strength, cohesion, internal friction angle, and percentage of silica, iron, and iron oxide in the Blasted block. Finally, using univariate and multivariate linear regression statistical analysis, equations to estimate the dimensions of the product (D50) resulting from the blasting using the physical, mechanical, and chemical characteristics of the rock masses of the explosive product. With coefficients of determination (R2) 92.48% for D50 were predicted...

Considering the widespread applications of perforated concrete pipes containing fluid flow in civil engineering, providing a suitable mathematical model for analyzing their stability and dynamic performance is essential. In this regard, a buried concrete pipe is formulated, taking into account the permeability of concrete materials and the surrounding soil, reinforced with silica nanoparticles. The structure is modeled using cylindrical shell elements and by employing the theory of elasticity. To calculate the force induced by the fluid flow inside the pipe, the Navier-Stokes equation is utilized. The influence of nanoparticles in the pipe is modeled using a mixing model, and the soil bed is simulated using vertical springs and shear layers. Finally, by applying Hamilton's principle, the governing equations of the structure are extracted. The Bezier finite element method is employed for structural analysis, and the effects of parameters such as the volume fraction of nanoparticles, concrete permeability, soil bed, fluid inside the pipe, and geometric parameters are investigated. The results of the analysis indicate that with an increase in the volume fraction of nanoparticles from zero to 3%, the maximum frequency and critical fluid velocity increase by 35% and 38%, respectively. Additionally, as the concrete permeability increases from zero to 6.0, the maximum frequency and critical fluid velocity decrease by 26% and 18%, respectively. These findings can contribute to the improvement and optimization of the design of concrete pipes containing fluid flow, enhancing our understanding of the dynamic behavior of these structures...

In this research, some options contracts of European and Asian types have been defined for construction stones in Lorestan. The Black-Scholes formula has been used for pricing European options and the Monte Carlo simulation method has been used to calculate the prices of Asian options. The calculation of option prices shows that Asian options have a lower price compared to European options, making them more attractive to investors.

A numerical solution based on the finite difference method is presented in this study which employs time-dependent parameters of surrounding rock mass of a circular tunnel. Applying the solution, the effect of time on induced stress and displacement is investigated. Moreover, the impact of support installation under time-dependent deformation of the surrounding mass is studied for various plastic behaviors.

Singularity is the characteristic of various non-linear phenomena, such as hydrothermal processes in the Earth's crust, which produce deposits with high metal concentrations. The final result of these processes is the appearance of fractal or multi-fractal features, and several methods exist to identify these features. The singularity distribution mapping method is one of the multi-fractal analyses developed based on the singularity index and as a tool for separating anomalies from the background or for separating local anomalies in a region. In this study, the multi-variable singularity mapping method was used to determine geochemical anomalies to establish the relationship between various elements in the Qara Cher exploration area, located 42 km southwest of the city of Saqez in Kurdistan province. The database contains 1104 litho-geochemical samples with 10 analyzed elements, including Au, As, Ag, Cu, Sb, Sn, Bi, Mo, Zn, and Pb. Due to the compositional nature of the variables and subsequent false correlations in the closed system, principal components analysis (PCA) was applied to the data under isometric log ratio (ilr) transformation. The relationship between As and Cu on the first and second principal components shows the independent function of gold in the study area. The application of the singularity mapping method has highlighted some promising and potential areas for future explorations. These areas could be important for mineralization due to the presence of phyllic alteration, iron oxides, sulfide minerals, and high-grade gold cells. Based on the singularity mapping results, two different hydrothermal mineralization systems of intermediate (mesothermal) to high thermal and epithermal to mesothermal are proposed, respectively; for the southern and northern parts of the Ghare Char area. Nevertheless, due to the mesothermal (orogenic) gold mineralization systems in the known Kervian and Ghlgholeh gold deposits, located in the vicinity of the Qareh Char area, and also the high concentration of As and Sb in these deposits, the possible presence of orogenic gold mineralization is more compared to the other types. Therefore, it is recommended to use the exploration criteria of the orogenic gold deposits for further exploration in the Qareh Char area.