查看更多>>摘要：Natural rock joint permeability deviates from the classic fluid flow governing equations due to the inher-ent fracture surface roughness(i.e.,contact points,spatial correlation,matching,varying aperture,iso-lated voids,infilling material,tortuosity and channellings)and engineering disturbance such as excavations.To improve the accuracy of fracture permeability evaluation,many efforts have been made in analytical,experimental,and numerical methods.This study reviews the modified mathematical gov-erning equations of fluid flow and classifies them based on different influencing factors,such as friction factor,aperture,tortuosity,inertia,and various in situ stress effects.Various experimental and simulation techniques for the coupled normal-and shear-stress flow problems were assessed,and their advantages and disadvantages were also analysed.Furthermore,different surface roughness descriptions and their impacts on mechanical and hydraulic behaviours were discussed,followed by the potential research directions for fracture flow problems.
查看更多>>摘要：The internal mechanism of the high hydrophobicity of the coal samples from the Pingdingshan mining area was studied through industrial,element,and surface functional group analysis.Laboratory testing and molecular dynamics simulations were employed to study the impact of three types of surfactants on the surface adsorption properties and wettability of highly hydrophobic bituminous coal.The results show that the surface of highly hydrophobic bituminous coal is compact,richin inorganic minerals,and poorly wettable and that coal molecules are dominated by hydrophobic functional groups of aromatic rings and aliphatic structures.The wetting performance of surfactants as the intermediate carrier to con-nect coal and water molecules is largely determined by the interaction force between surfactants and coal(Fs-c)and the interaction force between surfactants and water(Fs-w),which effectively improve the wettability of modified coal dust via modifying its surface electrical properties and surface energy.A new type of wetting agent with a dust removal rate of 89％has been developed through discovery of a compound wetting agent solution with optimal wetting and settling performance.This paper provides theoretical and technical support for removing highly hydrophobic bituminous coal dust in underground mining.
查看更多>>摘要：Slope stability prediction research is a complex non-linear system problem.In carrying out slope stability prediction work,it often encounters low accuracy of prediction models and blind data preprocessing.Based on 77 field cases,5 quantitative indicators are selected to improve the accuracy of prediction mod-els for slope stability.These indicators include slope angle,slope height,internal friction angle,cohesion and unit weight of rock and soil.Potential data aggregation in the prediction of slope stability is analyzed and visualized based on Six-dimension reduction methods,namely principal components analysis(PCA),Kernel PCA,factor analysis(FA),independent component analysis(ICA),non-negative matrix factoriza-tion(NMF)and t-SNE(stochastic neighbor embedding).Combined with classic machine learning meth-ods,7 prediction models for slope stability are established and their reliabilities are examined by random cross validation.Besides,the significance of each indicator in the prediction of slope stability is discussed using the coefficient of variation method.The research results show that dimension reduction is unnec-essary for the data processing of prediction models established in this paper of slope stability.Random forest(RF),support vector machine(SVM)and k-nearest neighbour(KNN)achieve the best prediction accuracy,which is higher than 90％.The decision tree(DT)has better accuracy which is 86％.The most important factor influencing slope stability is slope height,while unit weight of rock and soil is the least significant.RF and SVM models have the best accuracy and superiority in slope stability prediction.The results provide a new approach toward slope stability prediction in geotechnical engineering.
查看更多>>摘要：In the process of using the original key stratum theory to predict the height of a water-flowing fractured zone(WFZ),the influence of rock strata outside the calculation range on the rock strata within the cal-culation range as well as the fact that the shape of the overburden deformation area will change with the excavation length are ignored.In this paper,an improved key stratum theory(IKS theory)was pro-posed by fixing these two shortcomings.Then,a WFZ height prediction method based on IKS theory was established and applied.First,the range of overburden involved in the analysis was determined according to the tensile stress distribution range above the goaf.Second,the key stratum in the overburden involved in the analysis was identified through IKS theory.Finally,the tendency of the WFZ to develop upward was determined by judging whether or not the identified key stratum will break.The proposed method was applied and verified in a mining case study,and the reasons for the differences in the devel-opment patterns between the WFZs in coalfields in Northwest and East China were also fully explained by this method.
查看更多>>摘要：This work is part of a multi-phase project which aims to develop a sound methodology for rock fragmen-tation in underground mines using expansive cement.More specifically,it is the first phase of the project which focuses on laboratory tests to investigate the mechanical performance of expansive cement,also known as soundless chemical demolition agents(SCDA).This paper reports the results of laboratory tests conducted on instrumented thick-walled cylinders filled with expansive cement.Expansive pressure evo-lution and temperature variation with time are first examined for different borehole diameters.The clas-sical analytical method for expansive pressure estimation is validated with direct pressure measurement using high-capacity pressure sensor,and an empirical model is obtained.A new methodology based on iterative procedure is developed using axisymmetric finite element modelling and test results to derive the modulus of elasticity of the expansive cement at peak pressure.The results of this study show that the expansive pressure increases with borehole diameter when the rigidity of the steel cylinder is constant reaching 83 MPa for a 38.1 mm borehole.It is also shown that the expansive pressure decreases signif-icantly with increased cylinder rigidity for the same borehole diameter.The newly developed methodol-ogy revealed that the modulus of elasticity of expansive cement at peak pressure is estimated at 8.2 GPa.A discussion on the extension of the findings of this work to hard rock mining applications is presented.
查看更多>>摘要：The flotation separation of magnesite from calcium-containing minerals has always been a difficult sub-ject in minerals processing.This work studied the inhibition effects of carboxymethyl cellulose(CMC),sodium lignosulphonate,polyaspartic acid(PASP)and sodium silicate on flotation behaviors of magne-site,dolomite and calcite,providing guidance for the development of reagents in magnesite flotation.The micro-flotation results showed that among these four depressants,sodium silicate presented the strongest selectivity due to the highest recovery difference,and the flotation separation of magnesite from dolomite and calcite could be achieved by using sodium silicate as the depressant.Contact angle measurement indicated that the addition of sodium silicate caused the largest differences in surface wet-tability of the three minerals,which was in line with micro-flotation tests.Furthermore,zeta potential test,the Fourier transform infrared(FT-IR)spectroscopy and atomic force microscope(AFM)imaging were used to reveal the inhibition mechanism of sodium silicate.The results indicated that the domi-nated component SiO(OH)3-of sodium silicate could adsorb on minerals surfaces,and the adsorption of sodium silicate hardly affected the adsorption of NaOL on magnesite surface,but caused the reduction of NaOL adsorption on dolomite and calcite surfaces,thereby increasing the flotation selectivity.
查看更多>>摘要：This paper investigated the effects of potassium ferrate(PF)on the flotation performances of chalcopyrite and galena.The flotation results showed that PF obviously depressed galena,but had little effects on the floatability of chalcopyrite within pH range of 4.0-12.0.Zeta potential tests showed that the addition of PF induced the formation of more amounts of hydrophilic species on the surface of galena under an alka-line environment.Industrial grade O-isopropyl-N-ethyl thionocarbamate(IPETC)chemically adsorbed on the surface of the PF-treated chalcopyrite and galena after its addition.Contact angle measurements showed that with the addition of PF,the contact angle of the galena surface significantly decreased com-pared with the chalcopyrite surface.Localized electrochemical impedance spectroscopy(LEIS)tests showed that the addition of PF increased the impedance of the galena surface.X-ray photoelectron spec-troscopy(XPS)analyses revealed that the formation of hydrophilic species,namely lead sulfite,lead hydroxide and ferric hydroxide,on the galena surface,decreased its floatability in the presence of PF,while the formation of hydrophobic species,namely copper disulfide and elemental sulfur,on the chal-copyrite surface,maintained its floatability.Finally,a descriptive model for the reaction of PF with chal-copyrite and galena was proposed.
查看更多>>摘要：The adsorption of sodium oleate(NaOL)at the microfine hematite/aqueous solution interface was inves-tigated in this paper.Experimental research indicated that negative effects stemmed from the dissolution of the microfine hematite(D50=19.21 μm)could be effectively eliminated via the appropriate dosage of NaOL at alkali pH conditions.Solution chemistry calculation and adsorption test results indicated that RCOO-and(RCOO)222 ions were responsible for microfine hematite flotation at pH 8.2.Zeta potential and FTIR measurements confirmed the co-adsorption of molecular and ionic oleate species occurred at pH 8.2.X-ray photoelectron spectroscopy(XPS)results further indicated that oleate species interacted with hematite surfaces mainly through chemisorption,giving rise to molecule/colloid formation of oleate and Fe—OL complex compound.Time-of-flight secondary ion mass spectrometry(ToF-SIMS)results demonstrated that oleate species adsorbed onto the hematite surfaces with a thickness of a few nanome-ters.Furthermore,the normalized peak intensity of C4H7+ions on the hematite sample at pH 8.2 increased remarkably comparing with corresponding result of hematite sample at pH 6.8.The new findings of the present study well revealed the dissolution of microfine hematite and the pH effects on the hematite flotation,as well as the adsorption characteristics of oleate species.
查看更多>>摘要：To enhance the performance of traditional cationic collector,a novel poly hydroxy amine collector N-(2,3-Propanediol)-N-dodecylamine(PDDA)was designed by introducing one propylene glycol group into dodecylamine(DDA).It was prepared by a nucleophilic substitution reaction,which showed better sol-ubility and hydrophobicity than DDA and was firstly employed as the collector for the separation of hematite and quartz.Flotation tests showed that PDDA had an excellent flotation performance and sig-nificantly better selectivity than DDA.In addition,the flotation performance and adsorption mechanism of PDDA on hematite and quartz surfaces were studied using Fourier transform infrared spectroscopy(FT-IR),zeta potential and X-ray photoelectron spectroscopy(XPS)tests.These results demonstrated that the interaction between PDDA and the minerals'surfaces was mainly electrostatic adsorption and hydrogen bond,while PDDA tended to adsorb on the surfaces of quartz more than that of hematite.Performance optimization of amine collectors by introducing hydroxyl was also verified,which was of great meaning to the design,development,and application of the polyhydroxy cationic collector.In conclusion,PDDA could be used as a potential collector in the flotation separation of quartz and hematite.
查看更多>>摘要：The purpose of this study is to apply process mineralogy as a practical tool to further understand and ana-lyze the reasons for low leaching rates in the curing-leaching process of vanadium-bearing stone coal and to find a solution or improvement to optimize the leaching index.Using vanadium-bearing stone coal with the V2O5 mass fraction of 0.88％as the research object,the effects of particle size,mineral compo-sition,and sulfuric acid curing on the feed,intermediate,and final products of curing-leaching were ana-lyzed.The main vanadium-bearing minerals in the feed samples included sericite/illite,montmorillonite,kaolinite,limonite,and schreyerite.Through the penetration depth analysis of sulfuric acid,the reason for the high vanadium content in the coarse leaching residue(0.205％V2O5)was found,mainly due to the poor curing effect and incomplete washing after screening.Therefore,thorough washing after sieving and further optimizing the curing process are necessary.The vanadium content of the fine leaching resi-due(0.078％)was low and the curing-leaching effect was good.However,the vanadium content in the thickened residue(0.296％)exceeded that in the fine leaching residue,which was attributed to the neu-tralization reaction in the#1 thickener.To solve this problem,the neutralization and thickening pro-cesses should be performed in separate equipment.The analysis and detection of key products is helpful for identifying problems and improving the curing-leaching circuit process.
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