查看更多>>摘要：The differential evolution (DE) algorithm was deployed to calibrate microparameters of the DEM cohesive granular material.4 macroparameters,namely,uniaxial compressive strength,direct tensile strength,Young's modulus and Poisson's ratio,can be calibrated to high accuracy.The best calibration accuracy could reach the sum of relative errors REsum ＜ 0.1％.Most calibrations can be achieved with REsum ＜ 5％within hours or REsum ＜ 1％ within 2 days.Based on the calibrated results,microparameters uniqueness analysis was carried out to reveal the correlation between microparameters and the macroscopic mechanical behaviour of material:(1) microparameters effective modulus,tensile strength and normal-to-shear stiffness ratio control the elastic behaviour and stable crack growth,(2) microparame-ters cohesion and friction angles present a negative linear correlation that controls the axial strain and lateral strain prior to the peak stress,and (3) microparameters friction coefficient controls shear crack friction and slip mainly refers to the unstable crack behaviour.Consideration of more macroparameters to regulate the material mechanical behaviour that is dominated by shear crack and slip motion is high-lighted for future study.The DE calibration method is expected to serve as an alternative method to cal-ibrate the DEM cohesive granular material to its peak strength.
查看更多>>摘要：Dynamic disasters,such as rock burst due to the breaking of large area stiff roof strata,are known to occur in the hard rock strata of coal mines.In this paper,mechanical models of the fracturing processes of thick hard rock strata were established based on the thick plate theory and numerical simulations.The results demonstrated that,based on the fracture characteristics of the thick hard rock strata,four fracture models could be analyzed in detail,and the corresponding theoretical failure criteria were determined in detail.In addition,the influence of weak interlayer position on the fracture models and ground pressure of rock strata is deeply analyzed,and six numerical simulation schemes have been implemented.The results showed that the working face pressure caused by the independent movement of the lower layer is rela-tively low.The different fracture type of the thick hard rock strata had different demands on the working resistance of the hydraulic powered supports.The working resistance of the hydraulic powered supports required by the stratified movements was lower than that of the non-stratified movements.
Durjoy BaidyaMarco Antonio Rodrigues de BritoAgus P.SasmitoSeyed Ali Ghoreishi-Madiseh...
155-169页
查看更多>>摘要：The customarily discarded exhaust from the fossil fuel-based power plants of the off-grid mines holds the thermal potential to fulfill the heating requirement of the underground operation.This present research fills in an important research gap by investigating the coupling effect between a diesel exhaust heat recovery and an intake air heating system employed in a remote mine.An integrative approach compris-ing analytical,numerical,and experimental assessment has been adapted.The novel analytical model developed here establishes the reliability of the proposed mine heating system by providing comparative analysis between a coupled and a decoupled system.The effect of working fluid variation has been exam-ined by the numerical analysis and the possible improvement has been identified.Experimental investi-gations present a demonstration of the successful lab-scale implementation of the concept and validate the numerical and analytical models developed.Successful deployment of the fully coupled mine heating system proposed here will assist the mining industry on its journey towards energy-efficient,and sus-tainable mining practices through nearly 70％ reduction in fossil fuel consumption for heating intentions.
查看更多>>摘要：Here,the influence of grinding media with different shapes on the flotation performance of spodumene and its potential mechanism from microscale insights was investigated using a single mineral flotation experiment,X-ray diffraction (XRD) test,scanning electron microscopy combined with energy dispersive spectrometry (SEM-EDS),atomic force microscope (AFM) and X-ray photoelectron spectroscopy (XPS).The flotation data indicated that under anionic/cationic (sodium oleate (NaOL)/DDA) collectors system,the rod milled spodumene has a higher floatability than ball milled ones.XRD results confirmed that rod medium makes spodumene exposed more {110} and {100} planes,while ball medium makes spo-dumene exposed more {010} planes.The typical anisotropic surface of spodumene makes the surface of rod milled spodumene possess more Al sites,further confirmed by SEM-EDS and XPS results.Additionally,it was found that the rod milled spodumene presents a larger value of elongation and flat-ness,which are parameters closely related to bubble adhesion.AFM analysis indicated that rod milled products have a rougher surface,while ball milled products have a smoother surface.Consequently,the rod medium enhanced the adsorption of NaOL/DDA on the spodumene surfaces.This work provides theoretical guidance for optimizing the separation of spodumene from the perspective of grinding.
查看更多>>摘要：In present study,a novel organic depressant N-thiourea-maleamic acid (TMA) was synthesized and applied as a galena depressant in the flotation separation of Mo-Pb ores.The depression behaviors of TMA were tested through flotation experiments.A wider separation window for single minerals over 90.0％ was obtained at 30.0 mg/L TMA,confirming that TMA could depress galena significantly,while effected molybdenite floatability slightly.An effective separation was obtained for artificially mixed min-erals and actual Mo-Pb ores.The adsorption mechanism on galena was revealed by UV-Vis spectra,zeta potential tests,Fourier transform infrared spectroscopy (FT-IR) analysis,contact angle tests and X-ray photoelectron spectroscopy (XPS) analysis.The zeta potentials of galena became more negative and the contact angle of galena dropped from initial 74.36° to 57.8° with 30.0 mg/L TMA depressant,inferring that TMA had adsorbed on galena surface.The analysis results of UV-Vis spectra,FT-IR and XPS gave fur-ther evidence that TMA might chemisorb on galena surface via Pb sites on galena surface and the thiourea group in TMA molecular structure,while the carboxyl group played a role of hydrophilicity.
查看更多>>摘要：Marcasite (FeS2) is widespread in nature,its oxidation plays a vital role in acid mine drainage,mineral resource recovery,and photoelectric material applications.In this paper,the oxidation mechanism of marcasite has been studied for the first time using density functional theory (DFT).It is found that,unlike the oxidation of pyrite,the oxidation of marcasite merely occurs at surface S atoms.Under the coexis-tence of water and oxygen,S atoms around surface Fe atoms are replaced by O atoms.The surface S sites are initially oxidized to form S==O bonds,and continue to adsorb oxygen to gradually generate SO32-,SO42-species,and eventually FeSO4.In this process,H2O molecules participate in neither oxidation nor disso-ciation,and they are adsorbed on surface Fe sites in the form of molecules,i.e.,all O atoms in SO42-derive from oxygen rather than water molecules.
查看更多>>摘要：The flotation of diasporic bauxite is to separate diaspore (valuable mineral) from aluminosilicate miner-als (gangue minerals,mainly including kaolinite,illite and pyrophyllite),and the microscopic interaction force between the two types of minerals and air bubbles determines the separation efficiency.In this paper,based on the extended Derjaguin-Landau-Verwey-Overbeek (DLVO) theory,the van der Waals,electrostatic and hydrophobic interaction between particles of the four minerals mentioned above and air bubbles in collectorless solution were calculated first,and then diaspore and kaolinite were taken as examples to analyze the influence of various factors such as electrolyte concentration,mineral particle size,air bubble size,collector type (dodecylamine hydrochloride (DAH) and sodium oleate (NaOL)) and concentration,and pulp pH on the interactions between the particles of valuable mineral and gangue minerals and air bubbles.The results showed that the total extended DLVO interactions between the four minerals and air bubbles were repulsive in most cases in collectorless solution.The increase in elec-trolyte concentration reduced the interaction force or even changed the direction of the force under cer-tain circumstances.The addition of DAH and NaOL can reduce the adhesion energy barrier of kaolinite-bubble and diaspore-bubble respectively.Each type of minerals exhibited a specific interface interaction response with air bubbles in each collector with different pH values.The research results have theoret-ical guiding significance for the optimization and directional control of diasporic bauxite flotation conditions.
查看更多>>摘要：High humidity and high dust concentration in deep coal mines may severely challenge the performance of respirators worn by coal miners.This paper aims at quantitatively evaluating the respirators used in deep coal mines and providing scientific guidance for the respiratory protection of miners.Based on the self-designed in-situ PM2.5 collector,controllable PM2.5 generator,human breathing simulator,and respirator simulation testing system,under the simulated deep mine working condition,this study inves-tigated the effects of dust loading,wearing time,and dust concentration on the filtration efficiency,breathing resistance,and quality factor of N95 elastomeric respirators.With the increase of dust loading,the respirator filtration efficiency firstly decreased,then increased (minimum value 97.5％).The breathing resistance increased exponentially from 120 to 180 to 1020-1530 Pa,and the quality factor decreased logarithmically from 0.051 to 0.076 to 0.0058-0.0085 Pa-1.As the PM2.5 coal dust concentration increased from 5 to 50 mg/m3,the wearing time for the respirator breathing resistance to exceed 300 Pa reduced from 7 h to less than 1 h.One N95 elastomeric respirator is not able to perform an 8-h work shift.To avoid the excessive breathing resistance caused by dust loading,more filter cartridges are needed for coal miners.
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