A new approach for prediction of face advance rete (FAR) prior to mining operation and determination of the operation efficiency after mining operation in retreat longwall mining panel is presented based upon the conc...A new approach for prediction of face advance rete (FAR) prior to mining operation and determination of the operation efficiency after mining operation in retreat longwall mining panel is presented based upon the concepts of rock engineering system (RES). For this purpose, six longwall panels considered in Parvadeh-I coal mine. Seven major effective parameters on FAR was selected including coal mine roof rating, gas propagation, safety factor of longwall face, ratio of joint spacing to cutting depth at longwall face, longwall face inclination, panel width, floor rock mass rating. To performance evaluation of the presented model, the relationship between the average vulnerability indexes of advance operation with FAR was determined in considered panels with coefficient of determination (R2) equal to 0.884 that indicate relatively acceptable correlation and compatibility. Investigations of the research indicated that it is possible to determine the actual operation efficiency under fair conditions by a RES-based model. The inevitable reduction of FAR for each longwall panel was determined by presented model that the difference amount between the maximum possible practical face advance rate (FARmpp) and recorded actual face advance rate (FARa) indicate the operation efficiency. Applied approach in this paper can be used to prediction of FAR in retreat longwall mining panel for same conditions that can have many benefits, including better and more accurate planning for the sales market and mine operation. Also, presented method in this paper can be applied as a useful tool to determination of actual operation efficiency for other sections and extraction methods in coal mines.展开更多
In coal mining industry,with the depth growing of coal mines,the creep behaviours of coal and rock can extensively affect the mining safety,coalbed methane recovery and geo-sequestration.To acquire a better insight in...In coal mining industry,with the depth growing of coal mines,the creep behaviours of coal and rock can extensively affect the mining safety,coalbed methane recovery and geo-sequestration.To acquire a better insight into their creep characteristics,an efficient and robust researching technique,nanoindentation,was applied to investigate the creep performances of coal and rock samples obtained from two coal mines in the east of China.Creep characteristics were reflected by evaluating the curves of creep depth versus creep time of nanoindentation tests during the load-holding period at the peak load of 30 mN.These curves can be divided into two stages:transient stage and steady stage;and the time of load-holding period of 5 s,which is the dividing point between two stages,can efficiently avoid the influence of creep displacement on the unloading curves.The exponential function can perfectly fit creep curves and Kelvin model can be used to calculate the rheological parameters of coal and rock samples.Calculated results yield values for the creep modulus and viscosity terms of coal and rock.This study also settled a particular emphasis on the selection of the positions of indentations to obtain the rheological properties of mineralogical constituents in heterogonous coal and rock samples and their elastic aftereffect.展开更多
Pure aluminum samples were processed by equal channel angular pressing（ECAP） up to 10 passes at room temperature. The effects of the ECAP number of passes on the microstructure evolution, the mechanical properties, ...Pure aluminum samples were processed by equal channel angular pressing（ECAP） up to 10 passes at room temperature. The effects of the ECAP number of passes on the microstructure evolution, the mechanical properties, deformation homogeneity and corrosion behavior of the processed samples were fully investigated. The imposed strain resulted in an obvious reduction in the grain size from 390 μm before ECAP down to 1.8, 0.4, and 0.3 μm after ECAP up to 2, 4 and 10 passes, respectively. The microhardness, deformation homogeneity and tensile strength were increased while the elongation decreased with the increase of ECAP number of passes. Immersion tests, open circuit potential, Tafel polarization, cyclic polarization and potentiostatic measurements in 3.5% Na Cl solution revealed an obvious improvement in the corrosion resistance of ECAP processed samples compared with the as-cast sample. The increase of the number of passes can be used successfully in producing ultra-fine grained（UFG） bulk pure aluminum sample with a high misorientation angle, reasonably high mechanical properties and corrosion resistance.展开更多
The mining industry often uses shotcrete for ground stabilization. However, cracking within shotcrete is commonly observed, which delays production schedules and increases maintenance costs. A possible crack reduction...The mining industry often uses shotcrete for ground stabilization. However, cracking within shotcrete is commonly observed, which delays production schedules and increases maintenance costs. A possible crack reduction method is using expansive shotcrete mixture consisting of calcium sulfoaluminate cement(CSA), ordinary Portland cement(OPC), and calcium sulfate(CS) to reduce shrinkage. Furthermore, fibers can be added to the mixture to restrain expansion and impede cracking. The objective of this paper is to study the effects of nylon fiber, glass fiber, and steel fiber on an expansive shotcrete mixture that can better resist cracking. In this study, parameters such as density, water absorption, volume of permeable voids, unconfined compressive strength(UCS), splitting tensile strength(STS), and volume change of fiber-added expansive mixtures were determined at different time periods(i.e. the strengths on the 28 th day, and the volume changes on the 1 st, 7 th, 14 th, 21 st, and 28 th days). The results show that addition of fibers can improve mixture durability, in the form of decreased water absorption and reduced permeable pore space content. Moreover, the expansion of the CSA-OPC-CS mixture was restrained up to50% by glass fiber, up to 43% by nylon fiber, and up to 28% by steel fiber. The results show that the STS was improved by 57% with glass fiber addition, 43% with steel fiber addition, and 38% with nylon fiber addition. The UCS was also increased by 31% after steel fiber addition, 26% after nylon fiber addition, and16% after glass fiber addition. These results suggest that fiber additions to the expansive shotcrete mixtures can improve durability and strengths while controlling expansion.展开更多
Gold has been present throughout the history of mankind and used to make jewelry and coins, and recently, acquired several industrial uses. The price of gold in international market had a significant increasing, surpa...Gold has been present throughout the history of mankind and used to make jewelry and coins, and recently, acquired several industrial uses. The price of gold in international market had a significant increasing, surpassing 100% in the last five years. Thereby, deposits with low levels of gold content, gold with complex associations or in a very fine particle size became exploitable again, allowing new projects and expansion of existing ones. However, for maximum process efficiency is indispensable a deep knowledge of the characteristics of these minerals and their behavior in face of beneficiation processes. Consequently, an accurate routine for mineralogical and technological characterization is essential.展开更多
The creep behaviors in deep underground engineering structures,especially in soft rocks,have a remarkable impact on the long-term stability of the excavations,which finally leads to the high risk and failure of it.Acc...The creep behaviors in deep underground engineering structures,especially in soft rocks,have a remarkable impact on the long-term stability of the excavations,which finally leads to the high risk and failure of it.Accordingly,it is essential to recognize the time-dependent deformation through the investigation of this phenomenon.In this study,the creep behaviors of soft rocks were examined to help understand the underlying mechanism of the extended time-dependent deformation.Due to the limited results about the time-dependent properties of the constituents of the rock that reveal their heterogeneity,the targeting nanoindentation technique(TNIT),was adopted to investigate the viscoelastic characteristics of kaolinite and quartz in a two-constituent mudstone sample.The TNIT consists of identifications of mineralogical ingredients in mudstone and nanoindentation experiments on each identified constituent.After conducting experiments,the unloading stages of the typical indentation curves were analyzed to calculate the hardness and elastic modulus of both elements in mudstone.Additionally,the 180 s load-holding stages with the peak load of 50 mN were transformed into the typical creep strain-time curves for fitting analysis by using the Kelvin model,the standard viscoelastic model,and the extended viscoelastic model.Fitting results show that the standard viscoelastic model not only can perfectly express the nanoindentation creep behaviors of both kaolinite and quartz but also can produce suitable constants used to measure their creep parameters.The creep parameters of kaolinite are much smaller than that of quartz,which causes the considerable time-dependent deformation of the soft mudstone.Eventually,the standard viscoelastic model was also verified on the quartz in a sandstone sample.展开更多
Blasting in geological bodies is an industrial process acting in an environment characterized by high uncertainties (natural joints, faults, voids, abrupt structural changes), which are transposed into the process par...Blasting in geological bodies is an industrial process acting in an environment characterized by high uncertainties (natural joints, faults, voids, abrupt structural changes), which are transposed into the process parameters (e.g. energetic transfer to rock mass, hole deviations, misfires, vibrations, fly-rock, etc.). The approach to this problem searching for the "optimum" result can be ineffective. The geological environment is marked out by too many uncertainties, to have an "optimum" suitable to different applications. Researching for "Robustness" in a blast design gives rise to much more efficiency. Robustness is the capability of the system to behave constantly under varying conditions, without leading to unexpected results. Since the geology varies from site to site, setting a robust method can grant better results in varying environments, lowering the costs and increasing benefits and safety. Complexity Analysis (C.A.) is an innovative approach to systems. C.A. allows analyzing the Complexity of the Blast System and the criticality of each variable (drilling, charging and initiation parameters). The lower is the complexity, the more robust is the system, and the lower is the possibility of unexpected results. The paper presents the results obtained thanks to the C.A. approach in an underground gypsum quarry (Italy), exploited by conventional rooms and pillars method by drilling and blasting. The application of C.A. led to a reliable solution to reduce the charge per delay, hence reducing the impact of ground vibration on the surrounding structures. The analysis of the correlation degree between the variables allowed recognizing empirical laws as well.展开更多
Different types of nuclear parameters and corrosion behavior were deduced for carbon steel(AISI 1018),austenitic(304 SS),and duplex(2507 SS)stainless steel alloys.Three types of neutron energies as well as nine gamma ...Different types of nuclear parameters and corrosion behavior were deduced for carbon steel(AISI 1018),austenitic(304 SS),and duplex(2507 SS)stainless steel alloys.Three types of neutron energies as well as nine gamma ray energy lines(121.78-1407.92 keV)were used to evaluate the macroscopic neutron cross-sections(∑,cm^-1)and mass attenuation coefficients[σ,cm^2·g^-1)of gamma ray respectively.The corrosion behavior was investigated using different electrochemical techniques.The results showed that the stainless-steel alloys had a good attitude than that of carbon steel alloy for neutron and gamma ray parameters,especially the duplex stainless steel.The calculated values of mass attenuation coefficient using WinXcom computer program(Version 3.1),exhibited a very good agreement with the experimental values of that parameters.Moreover,the results indicated that duplex stainless-steel exhibited corrosion resistance higher than 304 SS and AISI 1018 steel alloys.展开更多
The enhancement of the physicochemical characteristics of fossil fuel has been the subject of extensive research to achieve better efficiency and reduced emissions. Diesel is one of the fossil fuels that are highly co...The enhancement of the physicochemical characteristics of fossil fuel has been the subject of extensive research to achieve better efficiency and reduced emissions. Diesel is one of the fossil fuels that are highly consumed in daily life. This paper focuses on the behavior of a refined diesel fuel when copper oxide nanoparticles are added. The resulting blend ofnano-diesel has been analyzed using a four-stroke engine under two loads indicating light vehicles and heavy duty vehicles. The nano-diesel was prepared by the aid of an ultrasonicator and a mechanical homogenizer. A base diesel was taken as a reference to distinguish the effect of the nanoparticles additives. Three different samples with different concentrations are utilized in this study. As a result, the fuel consumption, exhaust temperature, brake power, power losses and engine efficiency have been evaluated and compared to the base diesel in order to demonstrate and access the enhanced performance of the nano-fuel blend. The three concentrations conducted were 100 ppm, 200 ppm and 300 ppm of copper oxide nanoparticles. The results represented that the pure refinery diesel has low exhaust temperatures, high brake power and high efficiency as compared to the commercial diesel supplied from a gas station. In addition, 300 ppm copper oxide nano-diesel showed improvement in engine performances as compared to the other concentrations and pure diesel. In this context, lowest fuel consumption for both passenger cars and heavy duty vehicles was achieved, brake power for passenger cars only was improved and input power showed improvement however, exhaust temperature was the highest as for this fuel.展开更多
Due to the increased demand for energy resources these days,especially due to the Russian-Ukrainian war,the focus of the major countries is turning strongly towards improving oil production,especially heavy and extra ...Due to the increased demand for energy resources these days,especially due to the Russian-Ukrainian war,the focus of the major countries is turning strongly towards improving oil production,especially heavy and extra heavy oil,which represents 40%of the world oil reserve.Steam-based and thermal(EOR)procedures are promising techniques for recovering heavy oil reservoirs,but they suffer from a sequence of problems and complications that arise after long-term application.These complications comprise steam breakthrough,steam overlap,and steam/rock interactions.This research presents the currently applied techniques to maximize the productivity of heavy oil,such as steam injection,cyclic steam stimulation,in-situ combustion,and steam-assisted gravity drainage.Thermal technologies face numerous obstacles,as they are energy and water-intensive processes that are not environmentally friendly.The research also presents future trends in energy-saving and environmentally friendly techniques that enhance heavy oil recovery through vapor extraction(VAPEX)steam-solvent hybrid techniques,electromagnetic energy,sonication,and nanotechnology.The findings of this review reported that all the presented techniques focus on how to reduce the oil viscosity and in-situ upgrade the crude oil properties.In turn,these enhance both the productivity rate and oil recovery and minimize the production cost.This article can be considered a comprehensive review of thermal recovery methods in heavy and extra-heavy oil,in addition to screening criteria used for each method.展开更多
Reserve estimation is a key to find the correct NPV in a mining project. The most important factor in reserve estimation is the metal price. Metal price fluctuations in recent years were exaggerated, and imposed a hig...Reserve estimation is a key to find the correct NPV in a mining project. The most important factor in reserve estimation is the metal price. Metal price fluctuations in recent years were exaggerated, and imposed a high degree of uncertainty to the reserve estimation, and in consequence to the whole mine planning procedure. Real option approach is an efficient method of decision making in the uncertain conditions. This approach has been used for evaluation of defined natural resources projects until now. This study considering the metal price uncertainty used real option approach to prepare a methodology for reserve estimation in open pit mines. This study was done on a copper cylindrical deposit, but the achieved methodology can be adjusted for all kinds of deposits. This methodology was comprehensively described through the examples in such a manner that can be used by the mine planners.展开更多
This paper presents a methodology for studying low grade lateritic nickel ore, which usually presents complex mineralogy, with widespread nickel in several mineral phases. The study is focused on determining the miner...This paper presents a methodology for studying low grade lateritic nickel ore, which usually presents complex mineralogy, with widespread nickel in several mineral phases. The study is focused on determining the mineralogy and the distribution of nickel in the bearing minerals. Laboratory assays comprise homogenization, sampling and particle size analysis. Chemical analyses by X-ray fluorescence are performed in all fractions sizes, while mineralogical assessments by X-ray diffraction are carried out for head sample. The mineralogical composition of the samples and the partition of main elements in the bearing minerals are assayed by size fraction through automated image analysis software (MLA) coupled to a scanning electron microscope (SEM). The chemical compositions of the several minerals identified in MLA are determined during systematic observations on SEM with energy dispersive spectrometer (EDS).展开更多
In the light of wireless and non-fossil society based on portable electronics, electric vehicles, and smart grids, secondary batteries with higher energy density, faster charge, and safer operation are pursued persist...In the light of wireless and non-fossil society based on portable electronics, electric vehicles, and smart grids, secondary batteries with higher energy density, faster charge, and safer operation are pursued persistently [1]. Nowadays, commercial lithium(Li)-ion batteries have been practically applied in our daily life. However,the energy density of Li-ion batteries based on intercalation chemistry is approaching to the theoretical value due to the limited specific capacity of graphite anode(372 mA h g-1) [2].展开更多
New attention has been given to the resources of rare earth minerals over the last years. The natural shortage of these elements in the Earth’s crust and trade restrictions recently imposed by China, motivated the Br...New attention has been given to the resources of rare earth minerals over the last years. The natural shortage of these elements in the Earth’s crust and trade restrictions recently imposed by China, motivated the Brazilian Government to encourage new projects by inserting the exploitation of rare earths in the National Mining Plan, which deals with industry strategic issues in the country, helping to reduce current importation. The incentives can be in the choice of future targets for mineral exploration and for the development of laboratory studies and pilot scale processing tests.展开更多
The gemstone cutting is a useful process to create shapes on rocks and minerals. This is done through the steps sawing, grinding, faceting and polishing, thus providing better light reflection in the pavilion with spe...The gemstone cutting is a useful process to create shapes on rocks and minerals. This is done through the steps sawing, grinding, faceting and polishing, thus providing better light reflection in the pavilion with specific angles for each translucent mineral; brightness on the surface, aesthetic appreciation and their use in the jewellery industry.展开更多
It is important to understand the behaviour of voussoir beams in the design of underground excavations.There are a large number of discrepancies between the re sults obtained by differe nt researchers so far.To resolv...It is important to understand the behaviour of voussoir beams in the design of underground excavations.There are a large number of discrepancies between the re sults obtained by differe nt researchers so far.To resolve these discrepancies,physically testing the stress distribution at the mid span and abutment of voussoir beam is the key.In this paper,a simple two-block voussoir beam was built with loading system.The displacement and strain of the voussoir beam were measured by a digital image correlation system.The strain distribution along the joints of voussoir beams was firstly revealed.Then,the relationship between transverse load and midspan displacement of voussoir beam was presented.It is found that the stress distributions at the midspan and abutment are different both in shape and depth.The stress distribution is changing as the loading changes as well.展开更多
Application of geostatistical techniques when evaluating mineral deposits could reflect some geological characteristics which help through the stage of planning and production. In the present study<span style="...Application of geostatistical techniques when evaluating mineral deposits could reflect some geological characteristics which help through the stage of planning and production. In the present study<span style="font-family:Verdana;">,</span><span style="font-family:Verdana;"> an attempt has been done on two phosphate deposits at Elsebaiya area on both sides of the River Nile namely</span><span style="font-family:Verdana;">:</span><span style="font-family:;" "=""><span style="font-family:Verdana;"> Um Tondoba mine at Elsebaiya East area and Western River Nile mine in Elsebaiya West area. Depending on the available data, statistical analysis illustrated differences in the distribution of P</span><sub><span style="font-size:12px;font-family:Verdana;">2</span></sub><span style="font-family:Verdana;">O</span><sub><span style="font-size:12px;font-family:Verdana;">5</span></sub><span style="font-family:Verdana;"> % and ore thickness within the studied areas. Geostatistics used to start with constructing variograms for P</span><sub><span style="font-size:12px;font-family:Verdana;">2</span></sub><span style="font-family:Verdana;">O</span><sub><span style="font-size:12px;font-family:Verdana;">5</span></sub><span style="font-family:Verdana;"> % and thickness for the two phosphate deposits to be used with ordinary kriging models, also constructing cross variograms between P</span><sub><span style="font-size:12px;font-family:Verdana;">2</span></sub><span style="font-family:Verdana;">O</span><sub><span style="font-size:12px;font-family:Verdana;">5</span></sub><span style="font-family:Verdana;"> % and thickness to be used with cokriging models where the difference in the variogram parameters reflected a specific variation for each deposit horizontally and vertically. The ordinary kriging models and cokriging models illustrated different distribution behavior through both the two kriging techniques.</span></span>展开更多
A number of geotechnical analyses were carried out on selected carbonate rock samples from eight sites located in Egypt. This analysis was to assess the suitability of these rocks for building construction aggregate. ...A number of geotechnical analyses were carried out on selected carbonate rock samples from eight sites located in Egypt. This analysis was to assess the suitability of these rocks for building construction aggregate. The analyses included properties of uniaxial compressive strength, tensile strength, porosity, water absorption, and dynamic fragmentation. The success of building construction depends to a large extent on the availability of raw materials at affordable prices. Raw materials commonly used in the building industry include sands, gravels, clays and clay-derived products. Despite the widespread occurrence of carbonate rocks throughout Egypt, the low premium placed on their direct application in the building sector may be explained in two ways: firstly, the lack of awareness of the potential uses of carbonate rocks in the building construction industry(beyond the production of asbestos, ceiling boards, roof sheets and Portland cement); and secondly, the aesthetic application of carbonate rocks in the building construction depends mainly on their physical attributes, a knowledge of which is generally restricted to within the confines of research laboratories and industries. Thus this paper addresses the physical and mechanical characteristics of some Egyptian carbonate rocks, evaluating them for their suitability as building construction aggregates.展开更多
文摘A new approach for prediction of face advance rete (FAR) prior to mining operation and determination of the operation efficiency after mining operation in retreat longwall mining panel is presented based upon the concepts of rock engineering system (RES). For this purpose, six longwall panels considered in Parvadeh-I coal mine. Seven major effective parameters on FAR was selected including coal mine roof rating, gas propagation, safety factor of longwall face, ratio of joint spacing to cutting depth at longwall face, longwall face inclination, panel width, floor rock mass rating. To performance evaluation of the presented model, the relationship between the average vulnerability indexes of advance operation with FAR was determined in considered panels with coefficient of determination (R2) equal to 0.884 that indicate relatively acceptable correlation and compatibility. Investigations of the research indicated that it is possible to determine the actual operation efficiency under fair conditions by a RES-based model. The inevitable reduction of FAR for each longwall panel was determined by presented model that the difference amount between the maximum possible practical face advance rate (FARmpp) and recorded actual face advance rate (FARa) indicate the operation efficiency. Applied approach in this paper can be used to prediction of FAR in retreat longwall mining panel for same conditions that can have many benefits, including better and more accurate planning for the sales market and mine operation. Also, presented method in this paper can be applied as a useful tool to determination of actual operation efficiency for other sections and extraction methods in coal mines.
基金the projects of the Fundamental Research Funds for the Central Universities(2020ZDPY0221)the Guizhou Science and Technology Department([2020]2Y026)。
文摘In coal mining industry,with the depth growing of coal mines,the creep behaviours of coal and rock can extensively affect the mining safety,coalbed methane recovery and geo-sequestration.To acquire a better insight into their creep characteristics,an efficient and robust researching technique,nanoindentation,was applied to investigate the creep performances of coal and rock samples obtained from two coal mines in the east of China.Creep characteristics were reflected by evaluating the curves of creep depth versus creep time of nanoindentation tests during the load-holding period at the peak load of 30 mN.These curves can be divided into two stages:transient stage and steady stage;and the time of load-holding period of 5 s,which is the dividing point between two stages,can efficiently avoid the influence of creep displacement on the unloading curves.The exponential function can perfectly fit creep curves and Kelvin model can be used to calculate the rheological parameters of coal and rock samples.Calculated results yield values for the creep modulus and viscosity terms of coal and rock.This study also settled a particular emphasis on the selection of the positions of indentations to obtain the rheological properties of mineralogical constituents in heterogonous coal and rock samples and their elastic aftereffect.
文摘Pure aluminum samples were processed by equal channel angular pressing（ECAP） up to 10 passes at room temperature. The effects of the ECAP number of passes on the microstructure evolution, the mechanical properties, deformation homogeneity and corrosion behavior of the processed samples were fully investigated. The imposed strain resulted in an obvious reduction in the grain size from 390 μm before ECAP down to 1.8, 0.4, and 0.3 μm after ECAP up to 2, 4 and 10 passes, respectively. The microhardness, deformation homogeneity and tensile strength were increased while the elongation decreased with the increase of ECAP number of passes. Immersion tests, open circuit potential, Tafel polarization, cyclic polarization and potentiostatic measurements in 3.5% Na Cl solution revealed an obvious improvement in the corrosion resistance of ECAP processed samples compared with the as-cast sample. The increase of the number of passes can be used successfully in producing ultra-fine grained（UFG） bulk pure aluminum sample with a high misorientation angle, reasonably high mechanical properties and corrosion resistance.
基金financial support from Natural Sciences and Engineering ResearchCouncil(NSERC)(NSERC EGP 501335-16) along with the donated CSA cement
文摘The mining industry often uses shotcrete for ground stabilization. However, cracking within shotcrete is commonly observed, which delays production schedules and increases maintenance costs. A possible crack reduction method is using expansive shotcrete mixture consisting of calcium sulfoaluminate cement(CSA), ordinary Portland cement(OPC), and calcium sulfate(CS) to reduce shrinkage. Furthermore, fibers can be added to the mixture to restrain expansion and impede cracking. The objective of this paper is to study the effects of nylon fiber, glass fiber, and steel fiber on an expansive shotcrete mixture that can better resist cracking. In this study, parameters such as density, water absorption, volume of permeable voids, unconfined compressive strength(UCS), splitting tensile strength(STS), and volume change of fiber-added expansive mixtures were determined at different time periods(i.e. the strengths on the 28 th day, and the volume changes on the 1 st, 7 th, 14 th, 21 st, and 28 th days). The results show that addition of fibers can improve mixture durability, in the form of decreased water absorption and reduced permeable pore space content. Moreover, the expansion of the CSA-OPC-CS mixture was restrained up to50% by glass fiber, up to 43% by nylon fiber, and up to 28% by steel fiber. The results show that the STS was improved by 57% with glass fiber addition, 43% with steel fiber addition, and 38% with nylon fiber addition. The UCS was also increased by 31% after steel fiber addition, 26% after nylon fiber addition, and16% after glass fiber addition. These results suggest that fiber additions to the expansive shotcrete mixtures can improve durability and strengths while controlling expansion.
文摘Gold has been present throughout the history of mankind and used to make jewelry and coins, and recently, acquired several industrial uses. The price of gold in international market had a significant increasing, surpassing 100% in the last five years. Thereby, deposits with low levels of gold content, gold with complex associations or in a very fine particle size became exploitable again, allowing new projects and expansion of existing ones. However, for maximum process efficiency is indispensable a deep knowledge of the characteristics of these minerals and their behavior in face of beneficiation processes. Consequently, an accurate routine for mineralogical and technological characterization is essential.
基金The work presented in this paper was supported by the projects of"the Fundamental Research Funds for the Central Universities(2020ZDPY0221)""the Guizhou Science and Technology Department([2020]2Y026)".The authors are also grateful to the anonymous reviewers for carefully reading the manuscript and providing many helpful comments.Sun Changlun acknowledges,in particular,the powerful support received from his wife,Zhou Fan,over the years.
文摘The creep behaviors in deep underground engineering structures,especially in soft rocks,have a remarkable impact on the long-term stability of the excavations,which finally leads to the high risk and failure of it.Accordingly,it is essential to recognize the time-dependent deformation through the investigation of this phenomenon.In this study,the creep behaviors of soft rocks were examined to help understand the underlying mechanism of the extended time-dependent deformation.Due to the limited results about the time-dependent properties of the constituents of the rock that reveal their heterogeneity,the targeting nanoindentation technique(TNIT),was adopted to investigate the viscoelastic characteristics of kaolinite and quartz in a two-constituent mudstone sample.The TNIT consists of identifications of mineralogical ingredients in mudstone and nanoindentation experiments on each identified constituent.After conducting experiments,the unloading stages of the typical indentation curves were analyzed to calculate the hardness and elastic modulus of both elements in mudstone.Additionally,the 180 s load-holding stages with the peak load of 50 mN were transformed into the typical creep strain-time curves for fitting analysis by using the Kelvin model,the standard viscoelastic model,and the extended viscoelastic model.Fitting results show that the standard viscoelastic model not only can perfectly express the nanoindentation creep behaviors of both kaolinite and quartz but also can produce suitable constants used to measure their creep parameters.The creep parameters of kaolinite are much smaller than that of quartz,which causes the considerable time-dependent deformation of the soft mudstone.Eventually,the standard viscoelastic model was also verified on the quartz in a sandstone sample.
文摘Blasting in geological bodies is an industrial process acting in an environment characterized by high uncertainties (natural joints, faults, voids, abrupt structural changes), which are transposed into the process parameters (e.g. energetic transfer to rock mass, hole deviations, misfires, vibrations, fly-rock, etc.). The approach to this problem searching for the "optimum" result can be ineffective. The geological environment is marked out by too many uncertainties, to have an "optimum" suitable to different applications. Researching for "Robustness" in a blast design gives rise to much more efficiency. Robustness is the capability of the system to behave constantly under varying conditions, without leading to unexpected results. Since the geology varies from site to site, setting a robust method can grant better results in varying environments, lowering the costs and increasing benefits and safety. Complexity Analysis (C.A.) is an innovative approach to systems. C.A. allows analyzing the Complexity of the Blast System and the criticality of each variable (drilling, charging and initiation parameters). The lower is the complexity, the more robust is the system, and the lower is the possibility of unexpected results. The paper presents the results obtained thanks to the C.A. approach in an underground gypsum quarry (Italy), exploited by conventional rooms and pillars method by drilling and blasting. The application of C.A. led to a reliable solution to reduce the charge per delay, hence reducing the impact of ground vibration on the surrounding structures. The analysis of the correlation degree between the variables allowed recognizing empirical laws as well.
文摘Different types of nuclear parameters and corrosion behavior were deduced for carbon steel(AISI 1018),austenitic(304 SS),and duplex(2507 SS)stainless steel alloys.Three types of neutron energies as well as nine gamma ray energy lines(121.78-1407.92 keV)were used to evaluate the macroscopic neutron cross-sections(∑,cm^-1)and mass attenuation coefficients[σ,cm^2·g^-1)of gamma ray respectively.The corrosion behavior was investigated using different electrochemical techniques.The results showed that the stainless-steel alloys had a good attitude than that of carbon steel alloy for neutron and gamma ray parameters,especially the duplex stainless steel.The calculated values of mass attenuation coefficient using WinXcom computer program(Version 3.1),exhibited a very good agreement with the experimental values of that parameters.Moreover,the results indicated that duplex stainless-steel exhibited corrosion resistance higher than 304 SS and AISI 1018 steel alloys.
文摘The enhancement of the physicochemical characteristics of fossil fuel has been the subject of extensive research to achieve better efficiency and reduced emissions. Diesel is one of the fossil fuels that are highly consumed in daily life. This paper focuses on the behavior of a refined diesel fuel when copper oxide nanoparticles are added. The resulting blend ofnano-diesel has been analyzed using a four-stroke engine under two loads indicating light vehicles and heavy duty vehicles. The nano-diesel was prepared by the aid of an ultrasonicator and a mechanical homogenizer. A base diesel was taken as a reference to distinguish the effect of the nanoparticles additives. Three different samples with different concentrations are utilized in this study. As a result, the fuel consumption, exhaust temperature, brake power, power losses and engine efficiency have been evaluated and compared to the base diesel in order to demonstrate and access the enhanced performance of the nano-fuel blend. The three concentrations conducted were 100 ppm, 200 ppm and 300 ppm of copper oxide nanoparticles. The results represented that the pure refinery diesel has low exhaust temperatures, high brake power and high efficiency as compared to the commercial diesel supplied from a gas station. In addition, 300 ppm copper oxide nano-diesel showed improvement in engine performances as compared to the other concentrations and pure diesel. In this context, lowest fuel consumption for both passenger cars and heavy duty vehicles was achieved, brake power for passenger cars only was improved and input power showed improvement however, exhaust temperature was the highest as for this fuel.
文摘Due to the increased demand for energy resources these days,especially due to the Russian-Ukrainian war,the focus of the major countries is turning strongly towards improving oil production,especially heavy and extra heavy oil,which represents 40%of the world oil reserve.Steam-based and thermal(EOR)procedures are promising techniques for recovering heavy oil reservoirs,but they suffer from a sequence of problems and complications that arise after long-term application.These complications comprise steam breakthrough,steam overlap,and steam/rock interactions.This research presents the currently applied techniques to maximize the productivity of heavy oil,such as steam injection,cyclic steam stimulation,in-situ combustion,and steam-assisted gravity drainage.Thermal technologies face numerous obstacles,as they are energy and water-intensive processes that are not environmentally friendly.The research also presents future trends in energy-saving and environmentally friendly techniques that enhance heavy oil recovery through vapor extraction(VAPEX)steam-solvent hybrid techniques,electromagnetic energy,sonication,and nanotechnology.The findings of this review reported that all the presented techniques focus on how to reduce the oil viscosity and in-situ upgrade the crude oil properties.In turn,these enhance both the productivity rate and oil recovery and minimize the production cost.This article can be considered a comprehensive review of thermal recovery methods in heavy and extra-heavy oil,in addition to screening criteria used for each method.
文摘Reserve estimation is a key to find the correct NPV in a mining project. The most important factor in reserve estimation is the metal price. Metal price fluctuations in recent years were exaggerated, and imposed a high degree of uncertainty to the reserve estimation, and in consequence to the whole mine planning procedure. Real option approach is an efficient method of decision making in the uncertain conditions. This approach has been used for evaluation of defined natural resources projects until now. This study considering the metal price uncertainty used real option approach to prepare a methodology for reserve estimation in open pit mines. This study was done on a copper cylindrical deposit, but the achieved methodology can be adjusted for all kinds of deposits. This methodology was comprehensively described through the examples in such a manner that can be used by the mine planners.
文摘This paper presents a methodology for studying low grade lateritic nickel ore, which usually presents complex mineralogy, with widespread nickel in several mineral phases. The study is focused on determining the mineralogy and the distribution of nickel in the bearing minerals. Laboratory assays comprise homogenization, sampling and particle size analysis. Chemical analyses by X-ray fluorescence are performed in all fractions sizes, while mineralogical assessments by X-ray diffraction are carried out for head sample. The mineralogical composition of the samples and the partition of main elements in the bearing minerals are assayed by size fraction through automated image analysis software (MLA) coupled to a scanning electron microscope (SEM). The chemical compositions of the several minerals identified in MLA are determined during systematic observations on SEM with energy dispersive spectrometer (EDS).
基金supported by the National Key Research and Development Program (2016YFA0202500 and 2016YFA0200102)the National Natural Science Foundation of China (21676160, 21825501, and U1801257)Tsinghua University Initiative Scientific Research Program。
文摘In the light of wireless and non-fossil society based on portable electronics, electric vehicles, and smart grids, secondary batteries with higher energy density, faster charge, and safer operation are pursued persistently [1]. Nowadays, commercial lithium(Li)-ion batteries have been practically applied in our daily life. However,the energy density of Li-ion batteries based on intercalation chemistry is approaching to the theoretical value due to the limited specific capacity of graphite anode(372 mA h g-1) [2].
文摘New attention has been given to the resources of rare earth minerals over the last years. The natural shortage of these elements in the Earth’s crust and trade restrictions recently imposed by China, motivated the Brazilian Government to encourage new projects by inserting the exploitation of rare earths in the National Mining Plan, which deals with industry strategic issues in the country, helping to reduce current importation. The incentives can be in the choice of future targets for mineral exploration and for the development of laboratory studies and pilot scale processing tests.
文摘The gemstone cutting is a useful process to create shapes on rocks and minerals. This is done through the steps sawing, grinding, faceting and polishing, thus providing better light reflection in the pavilion with specific angles for each translucent mineral; brightness on the surface, aesthetic appreciation and their use in the jewellery industry.
文摘It is important to understand the behaviour of voussoir beams in the design of underground excavations.There are a large number of discrepancies between the re sults obtained by differe nt researchers so far.To resolve these discrepancies,physically testing the stress distribution at the mid span and abutment of voussoir beam is the key.In this paper,a simple two-block voussoir beam was built with loading system.The displacement and strain of the voussoir beam were measured by a digital image correlation system.The strain distribution along the joints of voussoir beams was firstly revealed.Then,the relationship between transverse load and midspan displacement of voussoir beam was presented.It is found that the stress distributions at the midspan and abutment are different both in shape and depth.The stress distribution is changing as the loading changes as well.
文摘Application of geostatistical techniques when evaluating mineral deposits could reflect some geological characteristics which help through the stage of planning and production. In the present study<span style="font-family:Verdana;">,</span><span style="font-family:Verdana;"> an attempt has been done on two phosphate deposits at Elsebaiya area on both sides of the River Nile namely</span><span style="font-family:Verdana;">:</span><span style="font-family:;" "=""><span style="font-family:Verdana;"> Um Tondoba mine at Elsebaiya East area and Western River Nile mine in Elsebaiya West area. Depending on the available data, statistical analysis illustrated differences in the distribution of P</span><sub><span style="font-size:12px;font-family:Verdana;">2</span></sub><span style="font-family:Verdana;">O</span><sub><span style="font-size:12px;font-family:Verdana;">5</span></sub><span style="font-family:Verdana;"> % and ore thickness within the studied areas. Geostatistics used to start with constructing variograms for P</span><sub><span style="font-size:12px;font-family:Verdana;">2</span></sub><span style="font-family:Verdana;">O</span><sub><span style="font-size:12px;font-family:Verdana;">5</span></sub><span style="font-family:Verdana;"> % and thickness for the two phosphate deposits to be used with ordinary kriging models, also constructing cross variograms between P</span><sub><span style="font-size:12px;font-family:Verdana;">2</span></sub><span style="font-family:Verdana;">O</span><sub><span style="font-size:12px;font-family:Verdana;">5</span></sub><span style="font-family:Verdana;"> % and thickness to be used with cokriging models where the difference in the variogram parameters reflected a specific variation for each deposit horizontally and vertically. The ordinary kriging models and cokriging models illustrated different distribution behavior through both the two kriging techniques.</span></span>
文摘A number of geotechnical analyses were carried out on selected carbonate rock samples from eight sites located in Egypt. This analysis was to assess the suitability of these rocks for building construction aggregate. The analyses included properties of uniaxial compressive strength, tensile strength, porosity, water absorption, and dynamic fragmentation. The success of building construction depends to a large extent on the availability of raw materials at affordable prices. Raw materials commonly used in the building industry include sands, gravels, clays and clay-derived products. Despite the widespread occurrence of carbonate rocks throughout Egypt, the low premium placed on their direct application in the building sector may be explained in two ways: firstly, the lack of awareness of the potential uses of carbonate rocks in the building construction industry(beyond the production of asbestos, ceiling boards, roof sheets and Portland cement); and secondly, the aesthetic application of carbonate rocks in the building construction depends mainly on their physical attributes, a knowledge of which is generally restricted to within the confines of research laboratories and industries. Thus this paper addresses the physical and mechanical characteristics of some Egyptian carbonate rocks, evaluating them for their suitability as building construction aggregates.
