Original Research Paper
K. Sultan Shah; M. H. Bin Mohd Hashim; K. Sh. Bin Ariffin
Abstract
The particles within the rock samples are present in extensive ranges of shapes and sizes, and their characterization and analysis exist with a considerable diversity. The prior research works have appraised the significance of the particle shape types and their effects on the geotechnical structures ...
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The particles within the rock samples are present in extensive ranges of shapes and sizes, and their characterization and analysis exist with a considerable diversity. The prior research works have appraised the significance of the particle shape types and their effects on the geotechnical structures and deficiencies by evaluating the uncertainty-related rock particle shape descriptors (PSDs). In this work, the Monte Carlo simulation (MCS) is used in order to present a framework to integrate the inherent uncertainty associated with PSDs. A tabletop microscope is used to measure the primary particle shape distribution for the sandstone samples. An open-source processing tool, ImageJ, is used in order to analyze PSDs. The probabilistic distribution of PSDs is acquired using MCS according to the relative frequency histogram of the input parameters. Additionally, a probabilistic sensitivity analysis is performed in order to evaluate the importance of the input parameters in PSDs. The sensitivity analysis results demonstrate that the major axis and area are the most influential parameters involved. The simulation results obtained have revealed that the proposed framework is capable of integrating the inherent uncertainties related to the particle shape.
Original Research Paper
H. Dao; Th. L. Pham; N. Ph. Hung
Abstract
Blasting has become a crucial work in mining operation. However, it produces high-intensity seismic waves which cause some serious troubles such as injure people, fly-rock, cracking, breaking and reducing the lifetime of adjacent buildings. In Vietnam, there have been many conflicts between residents ...
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Blasting has become a crucial work in mining operation. However, it produces high-intensity seismic waves which cause some serious troubles such as injure people, fly-rock, cracking, breaking and reducing the lifetime of adjacent buildings. In Vietnam, there have been many conflicts between residents and government about the compensation policy for these damages. The solution is proposed, in which a similar explosion is made and an instantaneous concussion meter is used to record the magnitude of the generated shock wave. The results received from this operation will be used to determine the effects of mining blast. In fact, that is an incorrect method because just by changing the type of explosives, the order, the explosives, etc., the shock wave will be significantly reduced. Nothing is ensured that another explosion causing a shock wave amplitude will not occur in the future. To solve this problem, this paper presents an online seismic wave monitoring system operating 24/24h, to transmit the recorded signal to an independent server located around the boundary of the mine. On the basis of the mechanism of generating explosive waves and the recording mechanism of shock waves, the authors have built a program to store records according to the permissible influence of Vietnam Standard and Circular 32/2019/TT- Vietnam Board of Directors.
Original Research Paper
M. Kamran
Abstract
Drillability is one of the significant issues in rock engineering. The drilling rate index (DRI) is an important tool in analyzing the drillability of rocks. Several efforts have been made by the researchers to correlate and evaluate DRI of rocks. The ensemble learning methods including the decision ...
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Drillability is one of the significant issues in rock engineering. The drilling rate index (DRI) is an important tool in analyzing the drillability of rocks. Several efforts have been made by the researchers to correlate and evaluate DRI of rocks. The ensemble learning methods including the decision tree (DT), adaptive boosting (AdaBoost), and random forest (RF) are employed in this research work in order to predict DRI of rocks. A drillability database with four parameters is compiled in this work. A relationship between the input parameters and DRI is established using the simple regression analysis. In order to train the model, different mechanical properties of rocks incorporating the uniaxial compressive strength (UCS), Brazilian tensile strength (BTS), brittleness test (S20), and sievers’ J-miniature drill value (Sj) are taken as the input variables. The original DRI database is randomly divided into the training and test sets with an 80/20 sampling method. Various algorithms are developed, and consequently, several approaches are followed in order to predict DRI of the rock samples. The model performance has revealed that RF predicts DRI with a high accuracy rate. Besides, the Monte Carlo simulations exhibit that this approach is more reliable in predicting the probability distribution of DRI. Therefore, the proposed model can be practiced for the stability risk management and the investigative design of DRI.
Original Research Paper
F. Khorram; O. Asghari; H. Memarian; A. Hoseein Morshedy; X. M. Emery
Abstract
The key input parameters for mine planning and all subsequent mining activities is based on the block models. The block size should take into account for the geological heterogeneity and the grade variability across the deposit. Providing grade models of smaller blocks is more complex and costly than ...
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The key input parameters for mine planning and all subsequent mining activities is based on the block models. The block size should take into account for the geological heterogeneity and the grade variability across the deposit. Providing grade models of smaller blocks is more complex and costly than larger blocks, but larger sizes cannot represent areas with high spatial variability accurately. Hence, a unique block size is not an optimal solution for modeling a mine site. This paper presented a novel algorithm to create an adaptive block model with locally varying block sizes aiming to control dilution and ore loss in Sungun porphyry copper deposit of Iran with a complex geometry characterized by multiple dikes. Three grade block models with different block sizes and simulated by direct block simulation are the inputs of algorithm. The output is a merged block model, assigning the smaller blocks to the complex zones, such as ore-waste boundaries, and larger blocks to the continuous and homogeneous zones of the ore body. The presented algorithm is capable to provide an accurate spatial distribution model with a fewer number of blocks in comparison to the traditional block modeling concepts.
Short Communication
M. Adil; S. Raza; I. Amin
Abstract
Despite the slope stability measures, rock falls are witnessed at section KM-37 of the Swat motorway (M-16), Khyber Pakhtunkhwa, Pakistan. The geotechnical data analysis of the site reveals that although the chances of plane/slope failures are reduced from 43% to 23% with the help of the existing design, ...
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Despite the slope stability measures, rock falls are witnessed at section KM-37 of the Swat motorway (M-16), Khyber Pakhtunkhwa, Pakistan. The geotechnical data analysis of the site reveals that although the chances of plane/slope failures are reduced from 43% to 23% with the help of the existing design, still there are possibilities of rock fall at the sight, which has also been witnessed during the field visits. The rock fall hazards are assessed through field tests and simulation, and significant stabilization measures are suggested. The rock fall tests are conducted, and then using the data obtained, the rock fall simulation is carried out using GeoRock 2D®. From a combination of the kinematic analysis and rock fall simulation, the hazard level along the slope ranges from moderate to high. The reason for this is the increasing velocity of the falling boulder and the impact of energy at the bottom of the slope. This is an indication of the risk, as the most hazardous area is at the toe of the slope, where the highway road is the main element at risk. Rock boulders of different shapes and sizes are released from a couple of benches in order to check their impacts on the highway. Based on the simulation, it is concluded that the spherical shaped boulders are released from higher benches covering more horizontal distances and reaching the highway with a higher bouncing heights at the toe of the slope than the cylindrical shaped boulders. The maximum bounce height of 7 m has been recorded at the toe of the slope. In order to reduce the impacts of energy and bounce heights of the boulders striking the slope surface, certain mitigation measures are suggested like a ditch of a specific size filled with sand or fine debris at the toe of the slope. Draping wire mesh on the slope surface and a retaining wall or fence would be greatly helpful and economical to reduce the rock falling hazards along the road side at section KM-37 of the Swat motorway.
Original Research Paper
N. Hajkazemiha; M. Shariat; M. Monavari; M. Ataei
Abstract
Mining and mineral industry have important role in supporting sustainable development of countries. Many countries rely on the income derived from natural resources, but the exploitation of the natural resources may impact the environment and destroy the ecosystem. Mining activities usually affect the ...
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Mining and mineral industry have important role in supporting sustainable development of countries. Many countries rely on the income derived from natural resources, but the exploitation of the natural resources may impact the environment and destroy the ecosystem. Mining activities usually affect the surrounding lands and ecosystems. The natural, social, and economic environments are part of this ecosystem that are directly involved in these activities. In order to reduce environmentally destructive effects of mining on ecosystem, some important measures must be taken to minimize the negative impacts of mining and related industries. In this paper, for the first time in Iran, a study was conducted to define and categorize the reclamation criteria in three largest iron ore mines. During this research, an attempt was made to establish, define and evaluate forty reclamation criteria. Since the number of criteria is high, to adopt the best practice in mine reclamation program, these criteria should be prioritized. The defined criteria ranked by mining experts, mining managers and related university professors according to their experience and knowledge. The raw collected data were evaluated, processed by Delphi-Fuzzy process and finally analyzed using the Multi-Criteria Decision Making (MCDM) method. The prioritized criteria can provide the authorities with a guideline to start reclamation planning based on the mining and environment requirements and budgeting and also to make the most fruitful, effective and low-cost decisions.
Original Research Paper
M. Shenavar; M. Ataee-pour; M. Rahmanpour
Abstract
The uncertainty-based mine evaluation and optimization have been regarded as a critical issue. However, it has received less attention in the underground mines than in the open-pit mines due to the diversity of the underground mining methods, and the underground mining parameters' complexity. The grade ...
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The uncertainty-based mine evaluation and optimization have been regarded as a critical issue. However, it has received less attention in the underground mines than in the open-pit mines due to the diversity of the underground mining methods, and the underground mining parameters' complexity. The grade and commodity price uncertainties play essential roles in mining projects. Mine planning by not incorporating these uncertainties is accompanied by risks. The evaluation and risk assessment of the mine plans is possible through evaluating the mineable reserve in the presence of such uncertainties. In the present work, we evaluate the effects of grade and commodity price uncertainties on the underground mining stope optimization and the resultant mineable reserve. In this regard, the stope boundary is studied both deterministically and stochastically in the presence of the grade and price uncertainties. For this purpose, in this work, we implement the conditional simulation in order to generate equally probable ore reserve models. Furthermore, we optimize the stope boundary using the floating-stope algorithm in each realization. Several decision support criteria including the 'mineable reserve,' 'metal-content,' 'profit,' and 'value-at-risk' are defined to assist the decision-maker in uncertain conditions. Finally, a procedure is defined in order to consider two types of uncertainty sources simultaneously in underground mining. It will guide the decision-maker toward the most appropriate stope boundary that best fits the mining company's requirements. The procedure is implemented in a bauxite mine, and the optimal stope boundary is determined concerning the different criteria.
Original Research Paper
M. Fathi; A. Alimoradi; H.R. Hemati Ahooi
Abstract
Scientific uncertainties make the grade estimation very complicated and important in the metallic ore deposits. This paper introduces a new hybrid method for estimating the iron ore grade using a combination of two artificial intelligence methods; it is based on the single layer-extreme learning machine ...
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Scientific uncertainties make the grade estimation very complicated and important in the metallic ore deposits. This paper introduces a new hybrid method for estimating the iron ore grade using a combination of two artificial intelligence methods; it is based on the single layer-extreme learning machine and the particle swarm optimization approaches, and is designed based on the location of the boreholes, depth of the boreholes, and drill hole information from an orebody, and applied for the ore grade estimation on the basis of a block model. In this work, the two algorithms of optimization clustering and neural networks are used for the iron grade estimation in the Choghart iron ore north anomaly in the central Iran. The results of the training and testing the algorithms indicate a significant ability of the optimized neural network system in the ore grade estimation.
Original Research Paper
S. Najafi Ghoshebolagh; A. Kamkar Rouhani; A.R. Arab Amiri; H. Bizhani
Abstract
As many gold deposits are associated with sulfide zones, and the direct exploration of gold deposits using the geophysical methods is very difficult due to its low amount in the sub-surface, the direct exploration of sulfide zones by the geophysical electrical resistivity and induced polarization (IP) ...
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As many gold deposits are associated with sulfide zones, and the direct exploration of gold deposits using the geophysical methods is very difficult due to its low amount in the sub-surface, the direct exploration of sulfide zones by the geophysical electrical resistivity and induced polarization (IP) methods may lead to the indirect exploration of gold deposits. The gold deposit in the Kervian area is located in the Kurdistan shear zone, and is directly related to the sulfide, silica, and carbonate alteration units. After acquiring the resistivity and IP data, 2D modeling of the data is made in order to indirectly identify the gold-bearing zones in the surveyed area. As some of the identified geophysical anomalies indicating the sulfide zones may not be associated with the economic amounts of gold, in order to obtain an exploration pattern for the gold deposit in the studied area, a combination of the geophysical data modeling and interpretation results with the geological information and other exploratory data is used to reduce the uncertainty in identifying the gold-bearing zones in the studied area. Thus, modeling and interpretation of the geophysical data lead to identify the sub-surface anomalies as the locations of possible gold mineralization in the area, and then the drilling points are suggested in the area. Considering the geological studies and chemical analysis of the samples taken from the drilled boreholes crossing some of the geophysical anomalies, we conclude that the geophysical anomalies occurring inside the phyllite and carbonate units in the area can contain an economic amount of gold, and thus are recommended as the top priority for further exploration.
Original Research Paper
M. Taghvaeenejad; M.R. Shayestefar; P. Moarefvand
Abstract
At different stages of mining, we always face a degree of uncertainty. Some of these uncertainties, such as the amount of reserve and grade of the deposit, are due to the inherent changes in the deposit and directly affect the technical and economic indicators of the deposit. On the other hand, the heavy ...
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At different stages of mining, we always face a degree of uncertainty. Some of these uncertainties, such as the amount of reserve and grade of the deposit, are due to the inherent changes in the deposit and directly affect the technical and economic indicators of the deposit. On the other hand, the heavy costs of the exploration sector often limit the amount of exploratory information, which necessitates the use of accurate estimation methods. In this work,we examines the modeling and estimation results using the conventional and simple kriging methods and the effects of the diverse indicators used in the classification of mineral storages or the parameters defining these indices. 127 exploratory boreholes with an average depth of 95 m are used to build the block model of the deposit in the Data Mine software. After the statistical studies, the 3D variographic studies are performed in order to identify the anisotropy of the region. A grade block model is constructed using the optimal variogram parameters.Then, using various methods to estimate the block model uncertainty including the kriging estimation variance, block error estimation, kriging efficiency and slope of regression, the mineral reserves are classified according to the JORC standard code. Based on different cut-off grades, the tonnage and average grade are calculated and plotted. In this work, an innovative quantitative method based on the grade-number and grade-volume fractal model is used to indicate the classification of mineral reserves. The use of fractal patterns due to the amplitude of the variation is greater and more important than the standard and provides us with a better understanding of the deposit changes per block. The existence of a minimal difference between the use of the standard and fractal patterns in the slope of the regression method indicates less error and is a proof of more reliable results.
Original Research Paper
M. Talaei; A. Mousavi; A. R. Sayadi
Abstract
Nowadays due to the existence of the economic and geological uncertainties and the increasing use of scenario-based project evaluation in the design of open-pit mines, it is necessary to find an exact algorithm that can determine the ultimate pit limit in a short period of time. Determining the ultimate ...
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Nowadays due to the existence of the economic and geological uncertainties and the increasing use of scenario-based project evaluation in the design of open-pit mines, it is necessary to find an exact algorithm that can determine the ultimate pit limit in a short period of time. Determining the ultimate pit limit is an important optimization problem that is solved to define what will be eventually extracted from the ground, and directly impacts the mining costs, revenue, choosing mining equipment, and approximation of surface infrastructures outside the pit. This problem is solved in order to maximize the non-discounted profit under the precedence relation (access) constraints. In this paper, the Highest-Level Push-Relabel (HI-PR) implementation of the push–relabel algorithm is discussed and applied in order to solve the ultimate pit limit optimization problem. HI-PR uses the highest-label selection rule, global update, and gap heuristics to reduce the computations. The proposed algorithm is implemented to solve the ultimate pit limit for the nine real-life benchmark case study publicly available on the Minelib website. The results obtained show that the HI-PR algorithm can reach the optimum solution in a less computational time than the currently implemented algorithms. For the largest dataset, which includes 112687 blocks and 3,035,483 constraints, the average solution time in 100 runs of the algorithm is 4 s, while IBM CPLEX, as an exact solver, could not find any feasible solution in 24 hours. This speeding-up capability can significantly improve the current challenges in the real-time mine planning and reconciliation, where fast and reliable solutions are required.
Original Research Paper
H. Haghgouei; A. Reza Kargar; M. H. Khosravi; M. Amini
Abstract
In many engineering constructions, the foundations should be built adjacent to each other. Therefore, the effect of interfering of close foundations should be considered in the design stage. In this research work, the effect of interference of closely separated foundations resting on a slope on the elastic ...
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In many engineering constructions, the foundations should be built adjacent to each other. Therefore, the effect of interfering of close foundations should be considered in the design stage. In this research work, the effect of interference of closely separated foundations resting on a slope on the elastic settlement is investigated by considering a semi-analytical solution. The distribution of stress due to the footing pressure in the slope is computed by a proposed Airy stress function, and then by employing the finite difference scheme, the displacement of the footings is calculated. The results obtained show that by increasing the distance between the foundations, the interference influence on the ratio of settlement will be diminished. However, this behavior is highly linked to the slope characteristics. For a slope with a height of 10 times of footing width, beyond an S/B ratio larger than 10, the effect of interference is not tangible, and the footings behave like an isolated foundation. By decreasing the slope height, this behavior will occur at a lower S/B.
Original Research Paper
M. Hosseini Nasab; M. Noaparast; H. Abdollahi
Abstract
In this research work, the bio-leaching of Co and Ni from an iron-rich laterite ore is assessed using the acidophilic heterotrophic (Delftia acidovorans)and autotrophic (Acidithiobacillus ferrooxidans) bacteria. The metabolic products of the acidophilic bacteria play an important role in bio-leaching. ...
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In this research work, the bio-leaching of Co and Ni from an iron-rich laterite ore is assessed using the acidophilic heterotrophic (Delftia acidovorans)and autotrophic (Acidithiobacillus ferrooxidans) bacteria. The metabolic products of the acidophilic bacteria play an important role in bio-leaching. The results obtained from the indirect bio-leaching indicate the highest nickel recoveries of up to 83.65% and 80.18%, respectively, by the supernatants of Acidithiobacillus ferrooxidans and Delftia acidovorans, both measured at 90 °C for 3 h with a stirring speed of 370 rpm and S/L of 0.1, while the corresponding cobalt recovery rates have reached 86.93% and 83.94%, respectively. The iron dissolution rates in these conditions for the two studied bacteria are 64.34% and 54.41%, respectively. The nickel and cobalt extractions by the indirect bio-leaching of Delftia acidovorans are, respectively, 29.84% and 23.75% higher than those for the direct bio-leaching, performed at 30 °C and 150 rpm of an incubator shaker for 30 days. For the indirect bio-leaching, the chemical control has a larger influence on the dissolution rate of the iron-rich laterite compared to the diffusion control. The activation energies of nickel and cobalt in the chemical control model are 40.07 and 39.08 kJ/mol, respectively.
Original Research Paper
V. Sarfarazi; H. Haeri; M. Fatehi Marji
Abstract
The tensile strength of the anisotropic rock-like material specimens is meastred directly in the laboratory using a new device converting the compressive loading to that of the tensile before the rock breakage. The specially prepared concrete slabs of dimensions 19 cm * 15 cm * 15 cm with a central hole ...
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The tensile strength of the anisotropic rock-like material specimens is meastred directly in the laboratory using a new device converting the compressive loading to that of the tensile before the rock breakage. The specially prepared concrete slabs of dimensions 19 cm * 15 cm * 15 cm with a central hole of 7.5 cm in diameter are tested experimentaly. The specimens are located in the compressive-to-tensile load converting device, and tested under a compressive loading rate of 0.02 MPa/s by the universal testing machine. The cubic slab samples are made in three different configurations to have the directions of 0°, 45°, and -45° with respect to the applied loading direction. In order to compare the direct tensile strength of the concrete samples with that of the indirect measuring tests, some Brazilian tests are also carried out on the concrete disc specimens prepared in the laboratory. By comparing the direct and indirect testing results of the concrete tensile strength, it can be concluded that the direct tensile strength values are somewhat lower than those of the indirect ones. The tensile strength values for the three different configurations of the concrete specimens are nearly the same.
Original Research Paper
H.R. Pasand Masoumi; A. Abdollahipour; Kh. Baghernia
Abstract
Determination of the optimum soil conditioning parameters in the earth pressure balance-tunnel boring machines (EPB-TBMs) plays an important role in reaching an optimum thrust force and advance speed. Silty-clay (CL-ML) in line 1 of the Ahwaz metro project is used in order to find the conditioning parameters ...
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Determination of the optimum soil conditioning parameters in the earth pressure balance-tunnel boring machines (EPB-TBMs) plays an important role in reaching an optimum thrust force and advance speed. Silty-clay (CL-ML) in line 1 of the Ahwaz metro project is used in order to find the conditioning parameters of slumps with different water contents and foam agents. The results obtained are a quantitative comparison between the parameters with different soil conditioning and water contents. Hence, the test results can be used to determine the most economical and technical conditioning parameters for a special condition of soil. The optimum quantity of foam expansion ratio (FER), foam injection ratio (FIR), percent ratio between the surfactant agent and the water volume (Cf), and cost for foam in this soil (based on the soil conditioning production cost) are 10, 157%, 2.07, 248 units, respectively. Soil conditioning with the optimum parameters obtained are tested in a TBM in two stages during excavation of 140 rings. This results in a lower soil conditioning cost and almost 40% higher advance speed.
Original Research Paper
H. Ebadi; P. Pourghahramani; B. Nemati akhgar
Abstract
Structural changes of mechanically-activated ilmenite during milling by a planetary mill are monitored and determined as a function of the milling time. The maximum specific BET surface area of 10.76 m2/g is obtained after 150 min of milling. The results obtained indicate that agglomeration of the particles ...
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Structural changes of mechanically-activated ilmenite during milling by a planetary mill are monitored and determined as a function of the milling time. The maximum specific BET surface area of 10.76 m2/g is obtained after 150 min of milling. The results obtained indicate that agglomeration of the particles occurs after 45 min of milling. The maximum X-ray amorphization degree of ca. 95% has been calculated after 150 min of milling. Estimation of the stored energy reveals that the X-ray amorphization degree has a dominant contribution to the excess enthalpy of the activated materials. The surface-weighted crystallite size in the ground ilmenite reaches 4.45 nm, which corresponds to the volume-weighted crystallite size of 8 nm and 11.18 nm obtained by the Williamson-Hall and Rietveld methods, respectively. After 150 min of mechanical activation, the root mean square strain, , increases to 0.78%, which corresponds to the strains of 1.43% and 1.04% obtained from the Williamson-Hall and Rietveld methods, respectively. Reduction in the crystallite size leads to the contraction of the ilmenite unit cell after 150 min. The reaction rate constant of the ilmenite dissolution increases by over 58 times after 150 min of milling. Activation energy of the dissolution reaction decreases from 57.45 kJ/mol to 41.09 kJ/mol after 150 min of milling.
Case Study
M. R. Shahverdiloo; Sh. Zare
Abstract
Hydraulic fracturing (HF) and hydraulic testing of pre-existing fractures (HTPF) are efficient hydraulic methods in order to determine the in-situ stress of rock mass. Generally, the minimum (Sh) and maximum (SH) horizontal principal stresses are measured by hydraulic methods; ...
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Hydraulic fracturing (HF) and hydraulic testing of pre-existing fractures (HTPF) are efficient hydraulic methods in order to determine the in-situ stress of rock mass. Generally, the minimum (Sh) and maximum (SH) horizontal principal stresses are measured by hydraulic methods; the vertical stress (SV) is calculated by the weight of the overburden layers. In this work, 37 HF and HTPF tests are conducted in a meta-sandstone, which has about 10% inter-layer phyllite. The artesian circumstance, considerable gap between the drilling and hydraulic tests in the long borehole, no underground access tunnel to rock cavern at the early stages of projects, and a simplified hypothesis theory of HF are the main challenges and limitations of the HF/HTPF measurements. Due to the instability in the long borehole, the drill rig type and borehole length are revised; also TV logger is added to the process of selection of the test’s deep. The HF/HTPF data is sequentially analyzed by the classic and inversion methods in order to achieve an optimum number of hydraulic tests. Besides, The SH magnitude in the inversion method is lower than the classic method; the relevant geological data and the faulting plan analysis lead to validate the SH and Sh magnitudes and the azimuths obtained by the classic method. The measured SH and Sh magnitudes are 7-17 MPa and 4-11 MPa, respectively; the calculated vertical stress magnitude is 6-14 MPa at the test locations. Indeed, the stress state is (SH > SV > Sh), and SH azimuth range is 56-93 degrees.
Original Research Paper
M. Azadi; M. Abedi; Gh. H. Norouzi Baghkameh
Abstract
< p>Attenuation of the signal received from sources causing anomalies and reduction of data resolution are the negative features of airborne measurements. Using a stable downward continuation method is a practical way to address these shortcomings. In this study, we investigated the efficiency ...
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< p>Attenuation of the signal received from sources causing anomalies and reduction of data resolution are the negative features of airborne measurements. Using a stable downward continuation method is a practical way to address these shortcomings. In this study, we investigated the efficiency of various stabilizers in achieving stable downward continued data. The purpose of this study is to select the most appropriate stabilizer(s) for this operation. We examined the various stabilizing functions by introducing them into the Tikhonov regularization problem. The results of research on synthetic airborne gravity and magnetic data showed that βL1 (the other definition of L1 norm) and SM (the smoothest model) stabilizers have the potential to be used in the stable implementation of the downward continuation method. These stabilizers performed better than the other in the three comparisons, including visual, quantitative (RMS error), and graphical comparisons. Also, by examining the airborne magnetic data related to the Esfordi district in Yazd province (Iran), it was found that in general the βL1 stabilizer is more suitable than the other stabilizing functions studied in this research.
Original Research Paper
Seyyed S. Ghannadpour; A. Hezarkhani
Abstract
In several uranium (U) prospecting projects in Iran, particularly Central Iran, the association and enrichment of rare earth elements (REEs) are known as the usual features. Sometimes the association of REEs and U with high economic perspective has caused that the relation between the rare earth and ...
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In several uranium (U) prospecting projects in Iran, particularly Central Iran, the association and enrichment of rare earth elements (REEs) are known as the usual features. Sometimes the association of REEs and U with high economic perspective has caused that the relation between the rare earth and radioactive elements is taken into consideration in other types of mineralization, and if there is any relation, radioactivity will be applied in the exploration of REEs. In the current work, sampling from Baghak anomaly in the Sangan mines is carried out based on the radioactivity and radiation measurement methods (as the optimal sampling pattern). In fact, the goal of this work is to survey the presence or absence of such a relation in a skarn mine, which is a different case study from Central Iran. In the case of presence, this will lead to a new exploration method and sampling pattern for REEs. The mineralogical studies (based on the optical and electronic microscopic observations), statistical investigations, and geochemical analyses are applied in this research work. The results obtained from the statistical studies show that the Baghak anomaly due to involving a significant amount of U, Ce, and La and a high concentration of REEs can be considered as one of the important mines. Spider diagrams and their geochemical investigations include the features that are typical of the subduction-related magmas in the calcalkaline volcanic arcs of the continental active margins. The chondrite-normalized REE pattern shows the enrichment of LREE, and a positive pattern close to flat HREE due to the entry of LREE ions into the allanites network. The mineralogical study results also confirm that REEs (especially Ce) are accumulated as a solid solution in the allanite minerals. Moreover, from the mineralogical, geochemical, and statistical analyses, it can be observed that in addition to the presence of such a relation in the mentioned mineralization (Central Iran mineralizations), there is an acceptable correlation between these elements in the Baghak iron-skarn mineralization. Eventually, it can be said that the idea and introduced method for the exploration of REEs in this work could present a new viewpoint to the decision-makers of this industry.
Original Research Paper
A. Majdi; M. Yazdani
Abstract
The hydraulic jacking refers to the process of crack growth of the pre-existing joints in the rock mass under grout pressure above the minimum in-situ stress. Thus it is essential to understand the resistance behavior of the joints and maximum grout pressure. This paper describes a novel method for determining ...
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The hydraulic jacking refers to the process of crack growth of the pre-existing joints in the rock mass under grout pressure above the minimum in-situ stress. Thus it is essential to understand the resistance behavior of the joints and maximum grout pressure. This paper describes a novel method for determining the hydraulic jacking occurrence in anisotropic rock mass based on the principle of fracture mechanics. This method is established on three stage developments: developing an equation in order to calculate the equivalent stress intensity factor at the joint tip, determining the fracture toughness by employing the Brazilian disc test with a loading rate of 0.1 MPa/s on the rock cored samples, and assessing the stability of joints using the maximum tangential stress criterion. By comparing the joint stress intensity factor and fracture toughness in the direction of rock anisotropy, the joint stability is evaluated. Then the maximum allowable grout pressure is analytically formulated as a function of fracture toughness in order to avoid the unwanted deformations in the joints (i.e. jacking) during grouting. In order to validate the proposed method, the data obtained from the boreholes used to construct water curtain at the Sanandaj Azad Dam in phyllite rocks are analyzed. Finally, it is concluded that the growth and expansion of the joints due to the instability under grout pressure leads to an increased cement take and the occurrence of hydraulic jacking. In addition, the proposed equation for computing maximum allowable grout pressure provides an acceptable agreement with the existing empirical rules and the results of the field data.
