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Gravel hardness effect on compaction characteristics of gravelly soil

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Journal of Mountain Science 2024年第4期21卷 1432-1443页

作者： SHI Yunfang LI Shengang JIANG Chen LIU Jinning school of resources and civil engineering Northeastern UniversityShenyang 110004China

The compaction characteristics of gravelly soil are affected by gravel *** investigate the evolution and influencing mechanism of different gravel hardness on the compaction characteristics of gravelly soil,heavy compaction tests and crushing tests were conducted on gravelly soils with gravels originated from hard,soft and extremely soft *** to orthogonal experiments and variance analysis,it was found that hardness has a significant impact on the maximum dry density of gravelly soil,followed by gravel content,and lastly,moisture *** gravel compositions with an average saturated uniaxial compressive strength less than 60 MPa,the order of compacted maximum dry density is soft gravels>hard gravels>extremely soft *** type of gravelly soil has a threshold for gravel content,with 60%for hard and soft gravels and 50%for extremely soft *** these thresholds,the compacted dry density decreases *** is a certain interaction between hardness,gravel content,and moisture *** hardness increases the influence of gravel content,whereas lower hardness increases the influence of moisture *** soils with the coarse aggregate(CA)between 0.7 and 0.8 typically achieve higher dry densities after *** addition,the prediction equations for the particle breakage rate and CA ratio in the Bailey method were proposed to estimate the compaction performance of gravelly soil *** results further revealed the compaction mechanism of different gravelly soils and can provide reference for subgrade filling construction.

关键词： Gravelly soil Hardness Compaction characteristics Crushing characteristics Particle breakage rate Bailey method

Mechanical properties and fracture surface roughness of thermally damaged granite under dynamic splitting

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Deep Underground Science and engineering 2024年第1期3卷 103-116页

作者： Yijin Qian Peng Jia Songze Mao Jialiang Lu school of resources and civil engineering Northeastern UniversityShenyangChina

In order to understand the mechanical properties and the fracture surface roughness characteristics of thermally damaged granite under dynamic splitting,dynamic Brazilian splitting tests were conducted on granite samples after thermal treatment at 25,200,400,and 600℃.Results show that the dynamic peak splitting strength of thermally damaged granite samples increases with increasing strain rate,showing obvious strain‐rate *** increasing temperature,thermally induced cracks in granite transform from intergranular cracks to intragranular cracks,and to a transgranular crack *** induced damages reduce the dynamic peak splitting strength and the maximum absorbed energy while increasing the peak radial *** fracture mode of the thermally damaged granite under dynamic loads is mode Ⅱ splitting *** using the axial roughness index Z2 a,the distribution ranges of the wedge‐shaped failure zones and the tensile failure zones in the fracture surfaces under dynamic Brazilian splitting can be effectively *** radial roughness index Z_(2)^(r)is sensitive to the strain rate and *** shows a linear correlation with the peak splitting strength and the maximum absorbed energy and a linear negative correlation with the peak radial strain.Z_(2)^(r)can be used to quantitatively estimate the dynamic parameters based on the models proposed.

关键词： dynamic splitting fracture surface roughness granite strain rate thermal treatment

Rockburst proneness considering energy characteristics and sample shape effects

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Journal of Rock Mechanics and Geotechnical engineering 2024年第7期16卷 2441-2465页

作者： Song Luo Fengqiang Gong Kang Peng Zhixiang Liu school of resources and Safety engineering Central South UniversityChangsha410083China school of civil engineering Southeast UniversityNanjing211189China

Accurate prediction of rockburst proneness is one of challenges for assessing the rockburst risk and selecting effective control *** study aims to assess rockburst proneness by considering the energy characteristics and qualitative information during rock *** representative rock types in cylindrical and cuboidal sample shapes were tested under uniaxial compression conditions and the failure progress was detected by a high-speed *** far-field ejection mass ratio(FEMR)was determined considering the qualitative failure information of the rock *** peak-strength energy impact index and the residual elastic energy index were used to quantitatively evaluate the rockburst proneness of both cylindrical and cuboidal ***,the performance of these two indices was analyzed by comparing their estimates with the *** results show that the accuracy of the residual elastic energy index is significantly higher than that of the peak-strength energy impact *** residual elastic energy index and the FEMR are in good agreement for both cylindrical and cuboidal rock *** is because these two indices can essentially reflect the common energy release mechanism characterized by the mass,ejection velocity,and ejection distance of rock *** suggests that both the FEMR and the residual elastic energy index can be used to accurately measure the rockburst proneness of cylindrical and cuboidal samples based on uniaxial compression test.

关键词： Rockburst proneness Sample shape Strain energy Energy release Far-field ejection mass ratio(FEMR)

A thermo-mechanical damage constitutive model for deep rock considering brittleness-ductility transition characteristics

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Journal of Central South University 2024年第7期31卷 2379-2392页

作者： FENG Chen-chen WANG Zhi-liang WANG Jian-guo LU Zhi-tang LI Song-yu school of civil and Hydraulic engineering Hefei University of TechnologyHefei 230009China school of Mechanics and civil engineering China University of Mining and TechnologyXuzhou 221116China school of resources and Environmental engineering Hefei University of TechnologyHefei 230009China

This paper developed a statistical damage constitutive model for deep rock by considering the effects of external load and thermal treatment temperature based on the distortion *** model parameters were determined through the extremum features of stress−strain ***,the model predictions were compared with experimental results of marble *** is found that when the treatment temperature rises,the coupling damage evolution curve shows an S-shape and the slope of ascending branch gradually decreases during the coupling damage evolution *** a constant temperature,confining pressure can suppress the expansion of *** the confining pressure increases the rock exhibits ductility characteristics,and the shape of coupling damage curve changes from an S-shape into a quasi-parabolic *** model can well characterize the influence of high temperature on the mechanical properties of deep rock and its brittleness-ductility transition characteristics under confining ***,it is suitable for sandstone and granite,especially in predicting the pre-peak stage and peak stress of stress−strain curve under the coupling action of confining pressure and high *** relevant results can provide a reference for further research on the constitutive relationship of rock-like materials and their engineering applications.

关键词： deep rock crack initiation threshold thermo-mechanical coupling statistical damage model distortion energy theory

Effect of temperature on suspension magnetization roasting of hematite using biomass waste as reductant:A perspective of gas evolution

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Journal of Central South University 2024年第6期31卷 1870-1887页

作者： CAO Yue SUN Yong-sheng HAN Yue-xin GAO Peng LI Yan-jun school of resources and civil engineering Northeastern UniversityShenyang 110819China National-local Joint engineering Research Center of High-efficient Exploitation Technology for Refractory Iron Ore resources Shenyang 110819China

The magnetization reduction of hematite using biomass waste can effectively utilize waste and reduce CO_(2) emission to achieve the goals of carbon peaking and carbon *** effects of temperatures on suspension magnetization roasting of hematite using biomass waste for evolved gases have been investigated using TG-FTIR,Py-GC/MS and gas composition *** mixture reduction process is divided into four *** the temperature range of 200-450℃ for mixture,the release of CO_(2),acids,and ketones is dominated in gases *** yield and concentration of small molecules reducing gases increase when the temperature increases from 450 to 900℃.At 700℃,the volume concentrations of CO,H_(2) and CH_(4) peak at 8.91%,8.90% and 4.91%,*** the suspension magnetization roasting process,an optimal iron concentrate with an iron grade of 70.86%,a recovery of 98.66% and a magnetic conversion of 45.70% is obtained at 700℃.Therefore,the magnetization reduction could react greatly in the temperature range of 600 to 700℃ owing to the suitable reducing *** study shows a detail gaseous evolution of roasting temperature and provides a new insight for studying the reduction process of hematite using biomass waste.

关键词： suspension magnetization roasting biomass pyrolysis gases evolution reduction behavior

Recent process developments in beneficiation and metallurgy of rare earths:A review

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Journal of Rare Earths 2024年第4期42卷 629-642页

作者： Shaokai Cheng Wenbo Li Yuexin Han Yongsheng Sun Peng Gao Xiaolong Zhang school of resources and civil engineering Northeastern UniversityShenyang110819China National-local Joint engineering Research Center of High-efficient Exploitation Technology for Refractory Iron Ore resources Shenyang110819China

Rare earth elements(REEs)are irreplaceable materials supporting low-carbon technology and equip-ment,and their commercial demand and strategic position are becoming increasingly *** the continuous depletion of rare earth(RE)resources,developing high-efficiency beneficiation and eco-friendly metallurgical processes has attracted widespread *** paper reviews the major minerals exploited for RE production and their deposits,as well as the beneficiation and metallurgical processes of RE ***,monazite,mixed RE ores,and ion-adsorption clays are the main raw materials in the world to ***-bearing ores(except ion-adsorption minerals)are generally beneficiated by flotation,gravity and magnetic separation *** mainstream metallurgical processes for bastnaesite,monazite and mixed RE concentrates are oxidation roasting-HCl leaching,caustic soda decomposition and high-temperature concentrated sulfuric acid roasting,***-adsorption clays are directly processed by in situ leaching-precipitation/solvent *** achieve the sustainable development of RE resources,it is essential to further explore innovative techniques to achievecomprehensive utilization and cleaner production.

关键词： Rare earths Beneficiation processes Metallurgical processes Cleaner production

Precise regulation of the phase transformation for pyrolusite during the reduction roasting process

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International Journal of Minerals,Metallurgy and Materials 2024年第1期31卷 81-90页

作者： Ruofeng Wang Peng Gao Shuai Yuan Yanjun Li Yingzhi Liu Cheng Huang school of resources and civil engineering Northeastern UniversityShenyang 110819China National-Local Joint engineering Research Center of High-efficient Exploitation Technology for Refractory Iron Ore resources Shenyang 110819China

The mechanism involved in the phase transformation process of pyrolusite (MnO_(2)) during roasting in a reducing atmosphere was systematically elucidated in this study,with the aim of effectively using low-grade complex manganese ore *** to single-factor experiment results,the roasted product with a divalent manganese (Mn^(2+)) distribution rate of 95.30% was obtained at a roasting time of 25 min,a roasting temperature of 700℃,a CO concentration of 20at%,and a total gas volume of 500 mL·min^(-1),in which the manganese was mainly in the form of manganosite (MnO).Scanning electron microscopy and Brunauer–Emmett–Teller theory demonstrated the microstructural evolution of the roasted product and the gradual reduction in the pyrolusite ore from the surface to the core Thermodynamic calculations,X-ray photoelectron spectroscopy,and X-ray diffractometry analyses determined that the phase transformation of pyrolusite followed the order of MnO_(2)→Mn_(2)O_(3)→Mn_(3)O_(4)→MnO phase by phase,and the reduction of manganese oxides in each valence state proceeded simultaneously.

关键词： pyrolusite phase transformation reduction roasting microstructural evolution reaction mechanism

Energy evolution and structural health monitoring of coal under different failure modes:An experimental study

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International Journal of Minerals,Metallurgy and Materials 2024年第5期31卷 917-928页

作者： Yarong Xue Xueqiu He Dazhao Song Zhenlei Li Majid Khan Taoping Zhong Fei Yang school of civil and resources engineering University of Science and Technology BeijingBeijing 100083China Zhong-an Academy of Safety engineering Beijing 100083China

Structural instability in underground engineering,especially in coal-rock structures,poses significant safety ***,the development of an accurate monitoring method for the health of coal-rock bodies is *** focus of this work is on understanding energy evolution patterns in coal-rock bodies under complex conditions by using shear,splitting,and uniaxial compression *** examine the changes in energy parameters during various loading stages and the effects of various failure modes,resulting in an innovative energy dissipation-based health evaluation technique for *** results show that coal bodies go through transitions between strain hardening and softening mechanisms during loading,indicated by fluctuations in elastic energy and dissipation energy *** tensile failure,the energy profile of coal shows a pattern of “high dissipation and low accumulation” before peak *** the other hand,shear failure is described by “high accumulation and low dissipation” in energy *** failure modes correlate with an accelerated increase in the dissipation energy before destabilization,and a significant positive correlation is present between the energy dissipation rate and the stress state of the coal samples.A novel mathematical and statistical approach is developed,establishing a dissipation energy anomaly index,W,which categorizes the structural health of coal into different danger *** method provides a quantitative standard for early warning systems and is adaptable for monitoring structural health in complex underground engineering environments,contributing to the development of structural health monitoring technology.

关键词： energy dissipation structural health monitoring early warning coal-rock mechanics failure mode

Literature overview of basic characteristics and flotation laws of flocs

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International Journal of Minerals,Metallurgy and Materials 2024年第5期31卷 943-958页

作者： Wanzhong Yin Yu Xie Zhanglei Zhu school of resources and civil engineering Northeastern UniversityShenyang 110819China College of Chemistry and Chemical engineering Xi’an University of Science and TechnologyXi’an 710054China

Flocculation flotation is the most efficient method for recovering fine-grained minerals,and its essence lies in flotation and recovery of *** physical characteristics of flocs are mainly determined by their apparent particle size and structure(density and morphology).Substantial researches have been conducted regarding the effect of floc characteristics on particle settling and water ***,the influence of floc characteristics on flotation has not been widely *** on the floc formation and flocculation flotation,this study reviews the fundamental physical characteristics of flocs from the perspectives of floc particle size and structure,summarizing the interaction between floc particle size and ***,it thoroughly discusses the effect of floc particle size and structure on floc floatability,further revealing the influence of floc characteristics on bubble collision and adhesion and elucidating the mechanisms of interaction between flocs and ***,it is observed that floc particle size is not the only factor influencing flocculation *** the appropriate apparent particle size range,flocs with a compact structure exhibit higher efficiency in bubble collision and adhesion during flotation,thereby resulting in enhanced flotation *** study aims to provide a reference for flocculation flotation,targeting the development of more efficient and refined flocculation flotation processes in the future.

关键词： flocs basic characteristics particle size and structure flotation laws bubbles