查看更多>>摘要：Sensor-based ore sorting is a technology used to classify high-grade mineralized rocks from low-grade waste rocks to reduce operation costs.Many ore-sorting algorithms using color images have been pro-posed in the past,but only some validate their results using mineral grades or optimize the algorithms to classify rocks in real-time.This paper presents an ore-sorting algorithm based on image processing and machine learning that is able to classify rocks from a gold and silver mine based on their grade.The algorithm is composed of four main stages:(1)image segmentation and partition,(2)color and tex-ture feature extraction,(3)sub-image classification using neural networks,and(4)a voting system to determine the overall class of the rock.The algorithm was trained using images of rocks that a geologist manually classified according to their mineral content and then was validated using a different set of rocks analyzed in a laboratory to determine their gold and silver grades.The proposed method achieved a Matthews correlation coefficient of 0.961 points,higher than other classification algorithms based on support vector machines and convolutional neural networks,and a processing time under 44 ms,promis-ing for real-time ore sorting applications.
查看更多>>摘要：The concept of the carbon cycle in the old goaf of a coal mine based on CO2 utilization and storage was put forward adhering to the principle of low-carbon development,utilization of space resources in old goafs,and associated gas resources development.Firstly,the evolution characteristics of overburden fissures in the goaf of the case was studied using a two-dimensional physical similarity simulation test,the sealing performance of the caprocks after stabilization was analyzed,and the fissures were counted and classi-fied.Then,the process of gaseous CO2 injection in the connected fissure was simulated by Ansys Fluent software,and the migration law and distribution characteristics of CO2 under the condition of gaseous CO2 injection were analyzed.Finally,the estimation models of free CO2 storage capacity in the old goaf were constructed considering the proportion of connected fissure and the effectiveness of CO2 injection.The CO2 storage capacity in the old goaf of the case coal mine was estimated.The results showed that a caprock group of''hard-thickness low-permeability hard-thickness"was formed after the caprock-fissures system in the goaf of the case tended to be stable vertically.The connected fissure,occlude cracks,and micro-fractures in the goaf accounted for 85.5%,8.5%,and 6%of the total fissures,respectively.Gaseous CO2 first migrated to the bottom of the connected fissure after CO2 was injected into the goaf,then spread horizontally along the bottom of the connected fissure after reaching the bottom,and finally spread longitudinally after filling the bottom of the entire connected fissure.The theoretical and effective storage capacities of free CO2 at normal temperature and pressure in the old goaf of the case were 9757 and 7477 t,respectively.The effective storage capacity of free CO2 at normal temperature and pressure in the old goaf after all minefield mined was 193404 t.The research can provide some reference for the coal mining industry to help the goal of''carbon peaking and carbon neutrality".
查看更多>>摘要：This paper investigates the frictional behavior of the infilled rock fracture under dynamic normal stress.A series of direct shear tests were conducted on saw-cut granite fractures infilled with quartz using a self-developed dynamic shear apparatus,and the effects of normal load oscillation amplitude,normal load oscillation period and sliding velocity were studied.The test results reveal that the shear response can be divided into three stages over a whole loading-unloading process,characterized by different time spans and stress variations.Generally,a smaller oscillation amplitude,a longer oscillation period and a fast shear velocity promote the stability of the friction system,which is also confirmed by the Coulomb failure criterion calculated based on the observed periodic apparent friction coefficient.The dynamic strengthening/weakening phenomenon is dependent on the oscillation amplitude and product of sliding velocity and oscillation period(vT).Also,the rate and state friction law incorporating the parameter α that characterizes the normal stress variation is employed to describe the dynamic friction coefficient but exhibits an incompetent performance when handling intensive variation in normal stress.Finally,the potential seismicity induced by oscillating normal stress based on the observed stress drop is analyzed.This work helps us understand the sliding process and stability evolution of natural faults,and its benefits for relative hazard mitigation.
Gde Pandhe Wisnu SuyantaraDaniyarov BerdakhHajime MikiTsuyoshi Hirajima...
703-716页
查看更多>>摘要：Enargite is typically associated with chalcocite.Owing to the similarity in the flotation behaviors of these minerals,both minerals are reported to concentrate in the conventional flotation circuit.However,inor-ganic arsenic in enargite can decrease the copper concentrate quality and increase the operating cost of processing this concentrate.Separating these minerals is important for cleaner copper production to avoid these effects.In this context,this study investigated the effect of hydrogen peroxide(H2O2)treat-ment on the flotation behavior of chalcocite and enargite.Flotation tests of pure and mixed minerals indi-cated that H2O2 treatment reduced the floatability of chalcocite and enargite by forming sulfate and copper hydroxide on their surfaces.Despite the detrimental effect of the H2O2 treatment,there was a nar-row window of H2O2 concentration for separating both minerals,in which enargite floated and chalcocite was depressed.This selective flotation behavior was caused by the rapid adsorption of potassium amyl xanthate(KAX)and lower surface oxidation of enargite compared with that of chalcocite.
查看更多>>摘要：Based on the underground powerhouse of Shuangjiangkou hydropower station,Octree theory is adopted to define the indices of the microseismic(MS)spatial aggregation degree and the deviation values of MS count and energy.The relationship between the MS multiple parameters and surrounding rock mass in-stability is established from three aspects:time,space,and strength.Supplemented by the center fre-quency of the signal evolution characteristics,A fuzzy comprehensive evaluation model and the evolution trend of the MS event center frequency are constructed to quantitatively describe the early warning state of the surrounding rock mass instability.The results show that the multilevel tree structure and voxels generated based on the Octree theory fit relatively well with the set of MS points in three-dimensional space.The fuzzy comprehensive evaluation model based on MS spatial aggregation and MS count and energy deviation values enables three-dimensional visualization of the potential damage area and damage extent of the surrounding rock mass.The warning time and potential damage zone quantified are highly consistent with the characteristics of MS precursors,with wide recognition and field investigation results,which fully validate the rationality and applicability of the proposed method.These findings can provide references for the early warning of surrounding rock mass instability in similar un-derground engineering.
查看更多>>摘要：The unfrozen water content(UWC)of rocks at low temperature is an important index for evaluating the stability of the rock engineering in cold regions and artificial freezing engineering.This study addresses a new method to estimate the UWC of saturated sandstones at low temperature by using the ultrasonic velocity.Ultrasonic velocity variations can be divided into the normal temperature stage(20 to 0℃),quick phase transition stage(0 to -5℃)and slow phase transition stage(-5 to -25℃).Most increment of ultrasonic velocity is completed in the quick phase transition stage and then turns to be almost a con-stant in the slow phase transition stage.In addition,the UWC is also measured by using nuclear magnetic resonance(NMR)technology.It is validated that the ultrasonic velocity and UWC have a similar change law against freezing and thawing temperatures.The WE(weighted equation)model is appropriate to es-timate the UWC of saturated sandstones,in which the parameters have been accurately determined rather than by data fitting.In addition,a linear relationship between UWC and ultrasonic velocity is built based on pore ice crystallization theory.It is evidenced that this linear function can be adopted to esti-mate the UWC at any freezing temperature by using P-wave velocity,which is simple,practical,and ac-curate enough compared with the WE model.
查看更多>>摘要：Aiming at the problem of temperature-mechanics-chemical(T-M-C)action encountered by rocks in underground engineering,sandstone was selected as the sample for acid corrosion treatment at pH 1,3,5 and 7,the acid corrosion treated samples were then subjected to high-temperature experiments at 25,300,600,and 900℃,and triaxial compression experiments were conducted in the laboratory.The experimental results show that the superposition of chemical damage and thermal damage has a sig-nificant impact on the quality,wave velocity,porosity and compression failure characteristics of the rock.Based on the Lemaitre strain equivalent hypothesis theory,the damage degree of rock material was described by introducing damage variables,and the spatial mobilized plane(SMP)criterion was adopted.The damage constitutive model can well reflect the stress-strain characteristics of the rock triaxial com-pression process,which verified the rationality and reliability of the model parameters.The experiment and constitutive model analyzed the change law of mechanical properties of rock after chemical corro-sion and high temperature thermal damage,which had certain practical significance for rock engineering construction.
查看更多>>摘要：Investigations on the dynamic mechanical properties and failure mechanisms of coal under in-situ stress is essential for the prevention of dynamic disasters in deep coal mines.Thus,a modified true triaxial Hopkinson bar was employed to explore the dynamic mechanical behaviors of coal at different confining pressures(0-20 MPa)and strain rates(40-220 s-1).The results show that the dynamic peak stress is pos-itively correlated with lateral static pre-stress σy and σz,but negatively correlated with axial static pre-stress σx.At approximate strain rates,increasing the lateral static pre-stress facilitates increasing the dynamic peak stress,but the minimum lateral static pre-stress is the primary factor limiting a significant increase in dynamic peak stress of coal.Furthermore,the dynamic differential stress is linearly related to the logarithm of strain rate,and the peak strain varies linearly with strain rate.However,there is no sig-nificant correlation between confining pressure and peak strain.Moreover,X-ray CT images and photo-graphic fracture observations of coal samples show the failure patterns under uniaxial and triaxial conditions are splitting failure and shear failure,respectively.The device provides a viable approach for fully comprehending the dynamic mechanical behaviors of rock-like material in complex stress conditions.
查看更多>>摘要：In this paper,using methyl cinnamate as raw material,the new cinnamic hydroxamic acid collector(CIHA)was synthesized by the hydroxylamine method.The collector performance of hydroxamic acid was investigated for scheelite and gangue calcite,and the flotation separation test of scheelite and calcite was carried out with CIHA as the collector.The interaction mechanism between hydroxamic acid and scheelite minerals has also been investigated through zeta potential,Fourier transform infrared spec-troscopy(FTIR)experiments,X-ray photoelectron spectroscopy(XPS)experiments,and density func-tional theory(DFT)calculation.The single mineral flotation test and artificially mixed ore showed that CIHA had an excellent collection effect and selectivity.Zeta potential,FTIR,and XPS showed that CIHA was adsorbed on the scheelite surface by strong chemical adsorption.The active group of CIHA was ana-lyzed through quantum chemical calculation.It was speculated that C=O and N-O bonds could synthe-size a five-membered chelated hydroxamic acid group with Ca element chelate on scheelite surface,changing hydrophobicity and making it more likely to emerge from the pulp.
查看更多>>摘要：This study aims to investigate the effect of a cationic-anionic mixed collector(dodecyltrimethyl ammo-nium bromide/sodium oleate(DTAB/NaOL)on the selective separation of apatite,dolomite,and potas-sium feldspar.Herein,several experimental methods,including flotation experiments,zeta-potential detection,microcalorimetry detection,XPS analysis and FTIR measurements,were used.The flotation tests showed that dolomite and potassium feldspar can be successfully removed from apatite simultane-ously when the molar ratio of DTAB to NaOL was 2∶1 with pH 4.5.Zeta-potential and microcalorimetry detection suggested that NaOL and DTAB were adsorbed on the surface of dolomite and potassium feld-spar respectively,and part of NaOL and DTAB formed co-adsorption on the surface of potassium feldspar to enhance the floatability of potassium feldspar.The XPS and FTIR spectra analysis demonstrated that the cationic collector,DTAB,was first adsorbed on the surface of potassium feldspar through electrostatic attraction in the DTAB/NaOL mixture system.Subsequently,the anionic NaOL collector and cationic DTAB collector form an electron neutralisation complex,thereby resulting in co-adsorption on the surface of potassium feldspar.NaOL was chemically reacted and adsorbed on dolomite surface,but almost no col-lector was adsorbed on apatite surface.Finally,the adsorption models of different collectors on mineral surface were obtained.
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