V. Bohanek, M. Dobrilović, B. Stimac Tumara, S. Stankovic
Shaped charges are widely used in many different fields. The two main users of shaped charges are the military, where shaped charges are used as a weapon against armoured targets, and the oil industry, to perforate wells. Very often, shaped charges are the subject of scientific research focused on optimising shaped charge parameters and increasing the efficiency of shaped charges. Considering a significant number of parameters affecting the penetration depth, the optimization of shaped charge parameters is a complex process. This paper describes research on the efficiency of small handmade shaped charges. In this research, two methods are used, the first one involves simulations with numerical software and the second one is site testing. AUTODYN software was used for the numerical simulations. One of the simulations was focused on the shape and velocity of the shaped charge jet and the second on the penetration of the jet into the target material. On-site efficiency of shaped charges at different standoff distances was tested. The experimental result was compared with the AUTODYN simulation result for hand-made shaped charges placed at a distance of 90 mm from the target material. The results of the simulations agree very well with the results of the site tests. Some advantages and disadvantages of each approach are also observed.
{"title":"The efficiency of a small sized hand-made shaped charge","authors":"V. Bohanek, M. Dobrilović, B. Stimac Tumara, S. Stankovic","doi":"10.17794/rgn.2022.2.7","DOIUrl":"https://doi.org/10.17794/rgn.2022.2.7","url":null,"abstract":"Shaped charges are widely used in many different fields. The two main users of shaped charges are the military, where shaped charges are used as a weapon against armoured targets, and the oil industry, to perforate wells. Very often, shaped charges are the subject of scientific research focused on optimising shaped charge parameters and increasing the efficiency of shaped charges. Considering a significant number of parameters affecting the penetration depth, the optimization of shaped charge parameters is a complex process. This paper describes research on the efficiency of small handmade shaped charges. In this research, two methods are used, the first one involves simulations with numerical software and the second one is site testing. AUTODYN software was used for the numerical simulations. One of the simulations was focused on the shape and velocity of the shaped charge jet and the second on the penetration of the jet into the target material. On-site efficiency of shaped charges at different standoff distances was tested. The experimental result was compared with the AUTODYN simulation result for hand-made shaped charges placed at a distance of 90 mm from the target material. The results of the simulations agree very well with the results of the site tests. Some advantages and disadvantages of each approach are also observed.","PeriodicalId":44536,"journal":{"name":"Rudarsko-Geolosko-Naftni Zbornik","volume":null,"pages":null},"PeriodicalIF":1.3,"publicationDate":"2022-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"68150752","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
V. Kostenko, O. Zavialova, Yu.P. Novikova, Оlha Bohomaz, Ya. Krupka, T. Kostenko
The objective of this paper is to substantiate the method of construction and design parameters of explosion-proof stoppings for the quick and safe remote sealing-off of the sources of complex fires and explosions in coal mines. A new method was designed for the remote erection of explosion-proof stoppings in mine workings and a mathematical model of mass transfer through the body of a stopping made of discrete material. Tactics were improved for the containment of underground fires and explosions due to rapid remote erection of explosion-proof stoppings. The technology of the quick erection of stoppings made of rocks crushed by an explosion for sealing-off of the emergency sections of the mine has been proposed. A computational model and a method for calculating the parameters of explosion-proof stoppings erected by the method of directed explosion have been created. The results of the calculations open the possibility to prepare the means of containment of dust explosions in advance and to improve the tactics of safe containment of explosions and fires.
{"title":"SUBSTANTIATING THE PARAMETERS OF QUICKLY ERECTED EXPLOSION-PROOF STOPPING","authors":"V. Kostenko, O. Zavialova, Yu.P. Novikova, Оlha Bohomaz, Ya. Krupka, T. Kostenko","doi":"10.17794/rgn.2022.4.12","DOIUrl":"https://doi.org/10.17794/rgn.2022.4.12","url":null,"abstract":"The objective of this paper is to substantiate the method of construction and design parameters of explosion-proof stoppings for the quick and safe remote sealing-off of the sources of complex fires and explosions in coal mines. A new method was designed for the remote erection of explosion-proof stoppings in mine workings and a mathematical model of mass transfer through the body of a stopping made of discrete material. Tactics were improved for the containment of underground fires and explosions due to rapid remote erection of explosion-proof stoppings. The technology of the quick erection of stoppings made of rocks crushed by an explosion for sealing-off of the emergency sections of the mine has been proposed. A computational model and a method for calculating the parameters of explosion-proof stoppings erected by the method of directed explosion have been created. The results of the calculations open the possibility to prepare the means of containment of dust explosions in advance and to improve the tactics of safe containment of explosions and fires.","PeriodicalId":44536,"journal":{"name":"Rudarsko-Geolosko-Naftni Zbornik","volume":null,"pages":null},"PeriodicalIF":1.3,"publicationDate":"2022-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"68153244","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Hani Al Khalaf, Gabriella Federer Kovacsne, Nagham Alhaj Mohammed, F. Remeczki
The main objective of this study is to enhance the poor performance of oil well cement in terms of mechanical properties by using pure polypropylene fibers. Polypropylene fibers were added in increasing concentrations from 0 to 0.1%, 0.3%, 0.5%, 0.7%, and 0.9% by weight of cement (BWOC). Rheological parameters, density, fluid loss, permeability, porosity, compressive strength, tensile strength, and flexural strength were all tested. A new method for measuring the tensile strength of cement samples in the presence of a casing is also evaluated in this research. In addition, the interfacial bonding shear strength, which represents the strength of cement adhesion to the casing, was measured using a new laboratory procedure. The influence of adding polypropylene fibers on rheology, density, and fluid loss can be ignored, according to the results of the experiments. The permeability and porosity of cement samples increased as the proportion of polypropylene fibers increased, according to the findings. Further, an increase in polypropylene fibers concentration up to 0.3% BWOC led to improving the mechanical properties at different curing times. The bonding strength of the casing cement interface improved with increasing polypropylene fibers concentration up to 0.5% BWOC.
{"title":"IMPROVING MECHANICAL PROPERTIES OF OIL WELL CEMENT USING POLYPROPYLENE FIBERS AND EVALUATING A NEW LABORATORY METHOD FOR MEASURING THE CASING CEMENT BONDING STRENGTH","authors":"Hani Al Khalaf, Gabriella Federer Kovacsne, Nagham Alhaj Mohammed, F. Remeczki","doi":"10.17794/rgn.2022.5.3","DOIUrl":"https://doi.org/10.17794/rgn.2022.5.3","url":null,"abstract":"The main objective of this study is to enhance the poor performance of oil well cement in terms of mechanical properties by using pure polypropylene fibers. Polypropylene fibers were added in increasing concentrations from 0 to 0.1%, 0.3%, 0.5%, 0.7%, and 0.9% by weight of cement (BWOC). Rheological parameters, density, fluid loss, permeability, porosity, compressive strength, tensile strength, and flexural strength were all tested. A new method for measuring the tensile strength of cement samples in the presence of a casing is also evaluated in this research. In addition, the interfacial bonding shear strength, which represents the strength of cement adhesion to the casing, was measured using a new laboratory procedure. The influence of adding polypropylene fibers on rheology, density, and fluid loss can be ignored, according to the results of the experiments. The permeability and porosity of cement samples increased as the proportion of polypropylene fibers increased, according to the findings. Further, an increase in polypropylene fibers concentration up to 0.3% BWOC led to improving the mechanical properties at different curing times. The bonding strength of the casing cement interface improved with increasing polypropylene fibers concentration up to 0.5% BWOC.","PeriodicalId":44536,"journal":{"name":"Rudarsko-Geolosko-Naftni Zbornik","volume":null,"pages":null},"PeriodicalIF":1.3,"publicationDate":"2022-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"68154262","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Mohammad Shami-Qalandari, M. Rahmanpour, S. M. Mahdi Mirabedi
Uncertainty-based stope boundary optimization is a complex part of underground mine planning, especially in mass mining projects and notably block caving. Besides, grade variation and grade uncertainty are significant sources of error in mining projects. This paper presents a procedure to determine a resilient block-cave stope boundary considering the ore grade uncertainties. The procedure applies the floating stope algorithm, the maximum upside/minimum downside, and the value at risk for design evaluation. The floating stope algorithm is customized for block caving and is used to determine the stope boundary over some simulated grade models. The idea fits into a multi-criteria decision-making problem. Finally, the most resilient stope boundary is selected by considering several criteria and the TOPSIS method. According to the results, the resilient stope boundary covers an area where the mineable reserve is 977 Mt with an average copper grade of 0.51%.
{"title":"DETERMINING A RESILIENT STOPE BOUNDARY FOR UNDERGROUND MASS MINING PROJECTS","authors":"Mohammad Shami-Qalandari, M. Rahmanpour, S. M. Mahdi Mirabedi","doi":"10.17794/rgn.2022.5.9","DOIUrl":"https://doi.org/10.17794/rgn.2022.5.9","url":null,"abstract":"Uncertainty-based stope boundary optimization is a complex part of underground mine planning, especially in mass mining projects and notably block caving. Besides, grade variation and grade uncertainty are significant sources of error in mining projects. This paper presents a procedure to determine a resilient block-cave stope boundary considering the ore grade uncertainties. The procedure applies the floating stope algorithm, the maximum upside/minimum downside, and the value at risk for design evaluation. The floating stope algorithm is customized for block caving and is used to determine the stope boundary over some simulated grade models. The idea fits into a multi-criteria decision-making problem. Finally, the most resilient stope boundary is selected by considering several criteria and the TOPSIS method. According to the results, the resilient stope boundary covers an area where the mineable reserve is 977 Mt with an average copper grade of 0.51%.","PeriodicalId":44536,"journal":{"name":"Rudarsko-Geolosko-Naftni Zbornik","volume":null,"pages":null},"PeriodicalIF":1.3,"publicationDate":"2022-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"68155404","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Zahra Jalili, A. Bahrami, M. Ghadri, B. N. Akhgar, F. Kazemi
Iron-bearing minerals are the most important interfering compounds that are found with bauxite reserves. The element iron has adverse effects on bauxite applications, including the use of bauxite in refractory soils. The purpose of this research is to investigate the possibility of iron removal from low-grade bauxite ores to utilize them in refractory industries. For achieving this purpose, iron removal tests were performed on bauxite samples with an alumina to silica modulus of 0.73. After determining the appropriate iron removal method among the magnetic separation, calcination, and leaching (with H2SO4 and HCl) processes, optimal separation conditions were determined by tests that were designed using the Taguchi method. According to leaching results, using HCl for raw feed (un-calcined) provided the best result for iron removal. During this test, Fe2O3 grade decreased from 5.14% to 0.08%, and the alumina to silica modulus increased to 0.75. Calcination of the concentrate obtained from this test has led to favorable results in reducing the Fe2O3 grade (0.04%) and increasing the Al2O3 grade. Afterwards, in tests designed by the Taguchi method, the effect of parameters such as time, process temperature, HCl concentration, and feed grain size on iron removal from bauxite by HCl leaching processes are discussed. According to the results, the best efficiency of iron removal for a feed grain size of 250 µm is achieved in the following conditions: 30% HCl, process temperature of 25°C, and process time of 120 minutes. In this case, iron removal efficiency and Fe2O3 grade in process concentrate are 92.78% and 0.56%, respectively.
{"title":"Leaching for iron removal from low-grade bauxite ore to access refractory instruction","authors":"Zahra Jalili, A. Bahrami, M. Ghadri, B. N. Akhgar, F. Kazemi","doi":"10.17794/rgn.2022.1.6","DOIUrl":"https://doi.org/10.17794/rgn.2022.1.6","url":null,"abstract":"Iron-bearing minerals are the most important interfering compounds that are found with bauxite reserves. The element iron has adverse effects on bauxite applications, including the use of bauxite in refractory soils. The purpose of this research is to investigate the possibility of iron removal from low-grade bauxite ores to utilize them in refractory industries. For achieving this purpose, iron removal tests were performed on bauxite samples with an alumina to silica modulus of 0.73. After determining the appropriate iron removal method among the magnetic separation, calcination, and leaching (with H2SO4 and HCl) processes, optimal separation conditions were determined by tests that were designed using the Taguchi method. According to leaching results, using HCl for raw feed (un-calcined) provided the best result for iron removal. During this test, Fe2O3 grade decreased from 5.14% to 0.08%, and the alumina to silica modulus increased to 0.75. Calcination of the concentrate obtained from this test has led to favorable results in reducing the Fe2O3 grade (0.04%) and increasing the Al2O3 grade. Afterwards, in tests designed by the Taguchi method, the effect of parameters such as time, process temperature, HCl concentration, and feed grain size on iron removal from bauxite by HCl leaching processes are discussed. According to the results, the best efficiency of iron removal for a feed grain size of 250 µm is achieved in the following conditions: 30% HCl, process temperature of 25°C, and process time of 120 minutes. In this case, iron removal efficiency and Fe2O3 grade in process concentrate are 92.78% and 0.56%, respectively.","PeriodicalId":44536,"journal":{"name":"Rudarsko-Geolosko-Naftni Zbornik","volume":null,"pages":null},"PeriodicalIF":1.3,"publicationDate":"2022-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"68148244","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The development of solid expandable tubular (SET) technology and products (open hole liner, open hole clad, cased hole liner, liner hanger, internal casing patch, etc.) has enabled operators to plan well design in a new way and solve various problems that arise during drilling and exploitation on land and offshore. By including an expandable open hole liner, monobore open hole liner or monobore openhole clad in well design, it is possible to achieve a slim hole design and/or resolve unwanted situations that occur during the drilling of problem zones with minimal hole size reduction and reach hydrocarbon reserves which cannot be achieved economically by conventional technology. By installing an expandable cased hole liner or internal casing patch in production wells to cover the intervals of a corroded casing or to close old perforations, it is possible to extend the life cycle of a production well and increase the final hydrocarbon recovery and speed up the return on investment. The aim of this paper is to systematically review the relevant literature and give an overview of solid expandable tubular technology and its applications in the petroleum industry, as well as the cementing technology of open hole expandable liners. The available data for 21 case studies of SET application in onshore and offshore wells were analyzed in detail. Based on an extensive review of the literature and analyzed data, it can be concluded that SET technology is being successfully applied worldwide and that expandable liners with a diameter of 114.3 mm to 339.72 mm are being run in wells to ever greater depths (up to 5166 m) and in ever more extreme downhole conditions.
{"title":"Application of Solid Expandable Tubulars in the Petroleum Industry","authors":"Nediljka Gaurina-Međimurec, Pavao Mesarić","doi":"10.17794/rgn.2022.1.14","DOIUrl":"https://doi.org/10.17794/rgn.2022.1.14","url":null,"abstract":"The development of solid expandable tubular (SET) technology and products (open hole liner, open hole clad, cased hole liner, liner hanger, internal casing patch, etc.) has enabled operators to plan well design in a new way and solve various problems that arise during drilling and exploitation on land and offshore. By including an expandable open hole liner, monobore open hole liner or monobore openhole clad in well design, it is possible to achieve a slim hole design and/or resolve unwanted situations that occur during the drilling of problem zones with minimal hole size reduction and reach hydrocarbon reserves which cannot be achieved economically by conventional technology. By installing an expandable cased hole liner or internal casing patch in production wells to cover the intervals of a corroded casing or to close old perforations, it is possible to extend the life cycle of a production well and increase the final hydrocarbon recovery and speed up the return on investment. The aim of this paper is to systematically review the relevant literature and give an overview of solid expandable tubular technology and its applications in the petroleum industry, as well as the cementing technology of open hole expandable liners. The available data for 21 case studies of SET application in onshore and offshore wells were analyzed in detail. Based on an extensive review of the literature and analyzed data, it can be concluded that SET technology is being successfully applied worldwide and that expandable liners with a diameter of 114.3 mm to 339.72 mm are being run in wells to ever greater depths (up to 5166 m) and in ever more extreme downhole conditions.","PeriodicalId":44536,"journal":{"name":"Rudarsko-Geolosko-Naftni Zbornik","volume":null,"pages":null},"PeriodicalIF":1.3,"publicationDate":"2022-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"68148367","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
V. Kostenko, O. Zavialova, S. Pozdieiev, T. Kostenko, Viktor Hvozd
The objective of this paper is to reveal the mechanism of creating conditions for the continuous explosion of coal dust by transferring seismic energy to coal dust located along the perimeter of a working. The ANSYS software package was used to model the movement of coal dust particles in the air under the influence of seismic waves caused by the action of an explosion. It was confirmed by modelling that seismic waves, provoked by an explosion, propagate in the rock mass at a higher velocity than the moving explosive front in the air of a working. The qualitative and quantitative behaviour of a layer of coal dust in the process of oscillation of the working walls under the influence of seismic waves during one second was described. The stage of dynamic loosening of the powder is supplemented by the initial period of the mechanism of explosion development, when there are no combustible concentrations of gas or coal traces in the air composition of the mine working before the incident. It is established that under the seismic influence at a distance of about 50 m from the hypocentre of the explosion, a layer of powder-like dispersed coal rises into the air forming a dust cloud, which is the initiator of further continuous development of the explosion spreading in a network of mine workings.
{"title":"Mechanism of development of coal dust continuous explosion in a network of mine workings","authors":"V. Kostenko, O. Zavialova, S. Pozdieiev, T. Kostenko, Viktor Hvozd","doi":"10.17794/rgn.2022.1.5","DOIUrl":"https://doi.org/10.17794/rgn.2022.1.5","url":null,"abstract":"The objective of this paper is to reveal the mechanism of creating conditions for the continuous explosion of coal dust by transferring seismic energy to coal dust located along the perimeter of a working. The ANSYS software package was used to model the movement of coal dust particles in the air under the influence of seismic waves caused by the action of an explosion. It was confirmed by modelling that seismic waves, provoked by an explosion, propagate in the rock mass at a higher velocity than the moving explosive front in the air of a working. The qualitative and quantitative behaviour of a layer of coal dust in the process of oscillation of the working walls under the influence of seismic waves during one second was described. The stage of dynamic loosening of the powder is supplemented by the initial period of the mechanism of explosion development, when there are no combustible concentrations of gas or coal traces in the air composition of the mine working before the incident. It is established that under the seismic influence at a distance of about 50 m from the hypocentre of the explosion, a layer of powder-like dispersed coal rises into the air forming a dust cloud, which is the initiator of further continuous development of the explosion spreading in a network of mine workings.","PeriodicalId":44536,"journal":{"name":"Rudarsko-Geolosko-Naftni Zbornik","volume":null,"pages":null},"PeriodicalIF":1.3,"publicationDate":"2022-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"68148736","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
During ore deposit development, vast networks of excavations are designed, and the volume of their intersections reaches 10%. At excavation intersections, the prediction of stress-strain state changes is complicated due to spatial geometry, the cross-coupling effect, construction sequence, etc. Mechanical properties of rocks, joint set parameters and the initial stress field also have a significant impact on stress redistribution. According to studies, up to 40% of the total number of failures in excavations occur during their intersections’ construction or reinforcing. Loads on the intersection support in accordance with existing methods are determined as for single excavations with an equivalent span and defined as the width of the larger excavation. The trend towards the intensification of mining, an increase in depth and the complexity of mining and geological conditions also complicate stress state assessment. Existing approaches need to be revised and updated for a more accurate prediction of the stress-strain state at intersections, and should consider spatial geometry, joint sets and initial stress field parameters. In this research, discrete element numerical modelling in 3DEC is done and the results are compared with existing empirical methods. Numerical models are created in a spatial setting and contain explicit representations of joints in the rock mass. Models are verified based on in-situ data, and the obtained results show a difference of up to 2 times in comparison with empirical results. This indicates that the reliability of the existing empirical methods is low, which may lead to stability loss on an intersection. Therefore, empirical methods should be updated. This can be done on the basis of numerical modelling, which shows sufficient convergence with in-situ data.
{"title":"Assessment of excavation intersections’ stability in jointed rock masses using the discontinuum approach","authors":"Anatolii Protosenya, M. Vilner","doi":"10.17794/rgn.2022.2.12","DOIUrl":"https://doi.org/10.17794/rgn.2022.2.12","url":null,"abstract":"During ore deposit development, vast networks of excavations are designed, and the volume of their intersections reaches 10%. At excavation intersections, the prediction of stress-strain state changes is complicated due to spatial geometry, the cross-coupling effect, construction sequence, etc. Mechanical properties of rocks, joint set parameters and the initial stress field also have a significant impact on stress redistribution. According to studies, up to 40% of the total number of failures in excavations occur during their intersections’ construction or reinforcing. Loads on the intersection support in accordance with existing methods are determined as for single excavations with an equivalent span and defined as the width of the larger excavation. The trend towards the intensification of mining, an increase in depth and the complexity of mining and geological conditions also complicate stress state assessment. Existing approaches need to be revised and updated for a more accurate prediction of the stress-strain state at intersections, and should consider spatial geometry, joint sets and initial stress field parameters. In this research, discrete element numerical modelling in 3DEC is done and the results are compared with existing empirical methods. Numerical models are created in a spatial setting and contain explicit representations of joints in the rock mass. Models are verified based on in-situ data, and the obtained results show a difference of up to 2 times in comparison with empirical results. This indicates that the reliability of the existing empirical methods is low, which may lead to stability loss on an intersection. Therefore, empirical methods should be updated. This can be done on the basis of numerical modelling, which shows sufficient convergence with in-situ data.","PeriodicalId":44536,"journal":{"name":"Rudarsko-Geolosko-Naftni Zbornik","volume":null,"pages":null},"PeriodicalIF":1.3,"publicationDate":"2022-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"68149545","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Mohammadmahdi Dinmohammadpour, M. Nikkhah, K. Goshtasbi, K. Ahangari
Determination of in-situ stress serves as an important step in the design and construction of civil and mining projects, among others. Conventional methods of the in-situ stress measurement are time- and cost-intensive. Therefore, the application of low-cost yet rapid methodologies for in-situ stress evaluation has been increasingly regarded by researchers. The Kaiser effect-based acoustic emission method is one of such novel approaches to the in-situ stress evaluation. Not only the point at which the Kaiser effect occurs, but also the mechanism of the Kaiser effect is of paramount importance. In this research, acoustic emission tests were conducted on phyllite rock samples under Brazilian tensile loading to collect a variety of acoustic data, including the amplitude, rise time, count, duration, and energy. Then, the Kaiser effect point was determined using the collected data on acoustic parameters, with its occurrence mechanism investigated. In addition, mathematical transformations were adopted to transform the acoustic signal from the time domain to the frequency domain, where the peak frequency was analyzed. The results of the RA/AF ratio analysis showed that the acoustic emission was sourced from tensile micro-cracks. Moreover, the high level of energy indicated a high intensity of crack formation at the Kaiser effect point. The large number of received hits showed that the count of generated cracks increases abruptly within the range of the Kaiser effect. In addition, the obtained high value of the peak frequency implied that the crack growth rate is high at the Kaiser effect point.
{"title":"THE MECHANISM OF THE KAISER EFFECT IN PHYLLITE UNDER INDIRECT TENSILE LOADING","authors":"Mohammadmahdi Dinmohammadpour, M. Nikkhah, K. Goshtasbi, K. Ahangari","doi":"10.17794/rgn.2022.3.2","DOIUrl":"https://doi.org/10.17794/rgn.2022.3.2","url":null,"abstract":"Determination of in-situ stress serves as an important step in the design and construction of civil and mining projects, among others. Conventional methods of the in-situ stress measurement are time- and cost-intensive. Therefore, the application of low-cost yet rapid methodologies for in-situ stress evaluation has been increasingly regarded by researchers. The Kaiser effect-based acoustic emission method is one of such novel approaches to the in-situ stress evaluation. Not only the point at which the Kaiser effect occurs, but also the mechanism of the Kaiser effect is of paramount importance. In this research, acoustic emission tests were conducted on phyllite rock samples under Brazilian tensile loading to collect a variety of acoustic data, including the amplitude, rise time, count, duration, and energy. Then, the Kaiser effect point was determined using the collected data on acoustic parameters, with its occurrence mechanism investigated. In addition, mathematical transformations were adopted to transform the acoustic signal from the time domain to the frequency domain, where the peak frequency was analyzed. The results of the RA/AF ratio analysis showed that the acoustic emission was sourced from tensile micro-cracks. Moreover, the high level of energy indicated a high intensity of crack formation at the Kaiser effect point. The large number of received hits showed that the count of generated cracks increases abruptly within the range of the Kaiser effect. In addition, the obtained high value of the peak frequency implied that the crack growth rate is high at the Kaiser effect point.","PeriodicalId":44536,"journal":{"name":"Rudarsko-Geolosko-Naftni Zbornik","volume":null,"pages":null},"PeriodicalIF":1.3,"publicationDate":"2022-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"68151465","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
There are numerous safety risk analysis techniques. Moreover, no ideal method exists for all companies; hence, the selection of the method most congruous with nature of the intended project, as well as the needs and resources of a mining company is of particular significance. To address the issue, a mathematical model has been developed with the aid of the Folchi-AHP method, whereby safety experts can opt for the best technique after multiplying an impacting factors matrix by a correlation matrix. The former is created by the safety team in the decision-making time, and includes 15 evaluation criteria, while the latter is comprised of the relative weight of each criterion to each technique. To find these weights, 22 methods were compared to each other in terms of 15 criteria by 10 safety experts using the analytic hierarchy process (AHP). To ease computations, an Excel program was developed and investigated in four mining projects.
{"title":"SELECTION OF THE SAFETY RISK ANALYSIS TECHNIQUE MOST COMPATIBLE WITH NATURE, REQUIREMENTS AND RESOURCES OF MINING PROJECTS USING AN INTEGRATED FOLCHI-AHP METHOD","authors":"Arman Hazrathosseini","doi":"10.17794/rgn.2022.3.4","DOIUrl":"https://doi.org/10.17794/rgn.2022.3.4","url":null,"abstract":"There are numerous safety risk analysis techniques. Moreover, no ideal method exists for all companies; hence, the selection of the method most congruous with nature of the intended project, as well as the needs and resources of a mining company is of particular significance. To address the issue, a mathematical model has been developed with the aid of the Folchi-AHP method, whereby safety experts can opt for the best technique after multiplying an impacting factors matrix by a correlation matrix. The former is created by the safety team in the decision-making time, and includes 15 evaluation criteria, while the latter is comprised of the relative weight of each criterion to each technique. To find these weights, 22 methods were compared to each other in terms of 15 criteria by 10 safety experts using the analytic hierarchy process (AHP). To ease computations, an Excel program was developed and investigated in four mining projects.","PeriodicalId":44536,"journal":{"name":"Rudarsko-Geolosko-Naftni Zbornik","volume":null,"pages":null},"PeriodicalIF":1.3,"publicationDate":"2022-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"68151773","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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