Table of Content

15 February 2024, Volume 53 Issue 2

Previous Issue   

Development and Prospect of Iron Ore Processing Technologies in China

HAN Yuexin, ZHANG Xiaolong, GAO Peng, LI Yanjun, SUN Yongsheng

2024, 53(2):  1. 

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Iron ore,as the most important raw material of iron and steel industry,is one of the important strategic mineral resources in China. The resource reserves of iron ore is abundant in China,but more than 97% of iron ores are low grade,which can be supplied to blast furnace only after treating by mineral processing. Over the years,with the joint efforts of many mineral processing workers,China′s iron ore processing technology has made considerable progress and development. This paper reviewed the development history of China′s iron ore processing technology. The applications of the main separation technologies including single low intensity magnetic separation,single flotation,gravity separation-magnetic separation-reverse flotation,magnetization roasting followed by magnetic separation in China′s iron ore concentrators were summarized. In addition,the current processing situations of China′s typical polymetallic associated iron ores including associated rare earth/ fluorite type iron ore, associated ilmenite type iron ore,associated polymetallic sulfide type iron ore and associated ferroboron type iron ore were introduced. Furthermore,the key equipments including cone crusher,high pressure roller mill,semi-autogenous mill,vertical ring pulsating high gradient magnetic separator,high frequency vibrating fine screen and stirring mill those affected the progress of iron ore processing technology were enumerated. It′s proposed that the future development direction of China′s iron ore processing should follow the principle of "high efficiency,energy saving,low carbon emission reduction",and the strategy of "available use of inferior quality and optimal use of high quality",develop the combined process of beneficiation and metallurgy,produce large and efficient equipment, develop low temperature flotation reagents, improve the intelligent control level, and strengthen the comprehensive utilization of resources.

Research Progress in Predicting Concentrate Grade Based on Flotation Foam Images

BU Xianzhong, YANG Yilin, WAN He

2024, 53(2):  25. 

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With the widespread application of artificial intelligence in mining production,it has become an inevitable trend to improve the accuracy and efficiency of ore grade prediction using computer vision technology. This article reviews the application and development process of traditional image processing algorithms and deep learning algorithms in ore grade prediction, and discusses future trends and challenges. Traditional image processing techniques extract features such as size,color, texture,and flow rate of foam images,and combine algorithms such as watershed segmentation,color moments,gray-level co-occurrence matrix,and local feature matching for feature extraction. These features have certain application value in scenarios with limited computing resources but have lower accuracy in tackling ore grade prediction tasks. Deep learning techniques,on the other hand,can extract high-level semantic features by constructing suitable model architectures and training them with large amounts of data. They have higher predictive accuracy and can achieve high performance and efficiency when used in conjunction with efficient computing devices such as Graphics Processing Units(GPUs). This article also introduces machine learning algorithms such as Support Vector Machines(SVM),Extreme Learning Machines(ELM),as well as deep learning algorithms such as Multilayer Perceptron(MLP),fully connected layers,and multi-scale feature fusion for feature mapping and grade prediction. The development history of deep learning models is also discussed. Finally,the current application status of industrial visual inspection systems is reviewed,and the challenges and future development trends in this field are analyzed from aspects such as data-driven models,multimodal data fusion,algorithm real-time performance,and dataset scale.

Research Progress in the Application of Red Mud Based Adsorbents

QIU Jun, YANG Wei, YAN Zhengqing, LIU Xiao, WU Peng, HUA Bingbing

2024, 53(2):  39. 

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Red mud is a kind of strong alkaline solid waste discharged in the process of alumina production. The annual emission is huge and the utilization rate is low,which causes serious waste of resources and environmental pollution. How to effectively recycle and utilize red mud is an urgent problem to be solved. Based on the hazard,physical and chemical properties and comprehensive utilization status of red mud,the application research progress of red mud-based adsorbents is reviewed in detail. Red mud has a fine particle size,high specific surface area and porosity,and contains a variety of active ingredients, which is suitable for treating wastewater containing pollution. However,if red mud is directly applied to sewage treatment,its treatment capacity is limited,and if highly alkaline red mud is directly used to treat sewage,the pH value of the solution will increase. Therefore,a series of activation processes are often used to activate red mud to prepare red mud-based adsorbents. The activation process not only improves the adsorption performance of red mud-based adsorbents,but also prevents secondary pol-lution caused by red mud to a certain extent. At present,the commonly used activation process of red mud mainly includes acid activation process,thermal activation process and neutralization activation process. The acid activation process can significantly improve the adsorption effect of red mud on anions. The thermal activation process can reduce the mass transfer resistance,high temperature pore-forming and mineral transformation,but the cost is high. Neutralizing activated red mud is often used to treat metal cations. The combined activation technology can comprehensively utilize the advantages of single activation process mentioned above,so that the activated red mud has better adsorption performance. However,the combined activation technology has more complicated operation and higher cost,which makes it difficult to be applied on a large scale in industry. At present,red mud-based adsorbents have been studied for the treatment of non-metallic anions,metal cations and organic pollutants in wastewater. In this paper,the examples of removing anions and heavy metal cations in wastewater by red mud-based adsorbents are listed,and the removal mechanism is expounded. Red mud-based adsorbents show good adsorption performance for some specific pollutants in wastewater,such as PO3- 4 ,F- ,AsO3- 4 ,etc. ,which mainly remove anionic pollutants in wastewater through surface complexation,ion exchange and precipitation. The red mud after activation modification can effectively remove heavy metal cations such as lead,copper,chromium and other heavy metal cations in water. For different target cations,the removal mechanism is also different,mainly including ion exchange,coprecipitation,electrostatic attraction," cation-π" interaction, complexation and physical adsorption. However,the removal mechanism of various pollutants by red mud-based adsorbents has not been fully clarified,and there are few studies on the competitive adsorption system in the presence of multiple pollutants. In summary,it is pointed out that in the future research of red mud-based adsorbents,it is an important research direction to find a convenient and cheap activation process to prepare new,efficient and environmentally friendly adsorbents and improve the adsorption performance of red mud-based adsorbents. At the same time,in the study of the preparation of red mud-based adsorbents and the treatment of waste,the research on the preparation mechanism and adsorption mechanism should be strengthened to provide theoretical guidance for the production and industrial application of red mud-based adsorbents.

Research Status on the Effect of Oxidation on Flotation of Copper-Sulfide Minerals

XUE Jiwei, LIU Qihong, LIU Tong, TIAN Yu, BU Xianzhong, WAN He, REN Dawei, LI Tangbo

2024, 53(2):  48. 

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The surfaces of most copper-sulfide minerals are easily oxidized,which have a significant effect on the flotation of the minerals and the adsorption of reagents on the surface of minerals. At present,researchers have conducted extensive research on the effect of oxidation on the flotation of copper-sulfide minerals,and have obtained remarkable achievements. Based on the factors affecting the surface oxidation of copper-sulfide minerals,this paper focuses on analyzing factors such as solution properties,mineral lattice defects on the surface oxidation of copper-sulfide minerals. The difficulty of the flotation of coppersulfide minerals after oxidized increased and the reasons are analyzed. On one hand,the metal ions increased generated from the oxidation and dissolution,which will cause serious interaction effect of copper-sulfide minerals,thus making it difficult to realize the flotation separation of copper-sulfide minerals. One the other hand,the strong hydrophilic metal oxides and hydroxides generated from the surface oxidation of copper-sulfide minerals will seriously weaken the effective adsorption of collectors, resulting in a decrease in the floatability of copper-sulfide minerals. Based on this,the flotation strengthening measurements and mechanism of copper-sulfide minerals after oxidized are discussed from two aspects:the shedding method of the oxidation layer and the surface regulation method of copper-sulfide minerals after oxidized. At last,the relevant suggestions were proposed about the flotation strengthening measurements of oxidized copper-sulfide minerals. This could provide reference for achieving the effective flotation recovery of oxidized copper-sulfide minerals.

Research Progress in the Flotation Reagent of Molybdenite and Talc

LIU Qiqiao, CHE Yuhang, CHEN Wei, LIU Sheng, ZHAO Gang, YANG Liu

2024, 53(2):  56. 

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Molybdenite and talc are closely associated with each other and have similar floatability,so their efficient flotation separation is always a difficulty in flotation field. At present,the separation process of molybdenite and talc mainly includes positive flotation by floating molybdenite and reverse flotation by removing talc and then floating molybdenum. Both processes involve the inhibitor of molybdenite and talc and collector of molybdenite. In recent years,many new reagents for molybdenetalc separation have been reported,but there is a lack of systematic summary and analysis of the similarity,variability and difference of these reagents in terms of chemical composition,functional groups and steric configuration. Therefore,the research progress on the relationship between crystal structure and hydrophilic/ hydrophobic properties of molybdenite and talc is summarized. The types,adsorption mechanism and application effect of molybdenite and talc inhibitors are discussed in detail. The structure-activity relationship of inhibitors is analyzed,and the latest progress in molecular design of molybdenite/ talc inhibitors and molybdenite collectors is introduced. By summarizing the crystal structure and hydrophilic/ hydrophobic characteristics of the basal/ edge plane,it is found that the two minerals have strong hydrophilic properties due to ionic dissolution,oxidation and other behaviors on the edge planes. However,as the basal plane occupies more than 90% of the overall surface area,the two minerals show good natural hydrophobicity as a whole,which is the fundamental reason for the difficulty in flotation separation. Water-soluble metal salt is the traditional inorganic inhibitor of molybdenite and talc,but it has the disadvantages of large dosage and poor selectivity,so its application is limited. Organic polymers are the research focus of molybdenite/ talc inhibitors, which are often acidic in the pulp. The higher the alkalinity of the surface of molybdenite/ talc,the stronger the interaction between them. When the adsorption is "strong interactions",this acid-base interaction may appear as chemisorption;when the adsorption is "weak interaction",the effect is manifested as hydrophobic attraction,hydrogen bond attraction,electrostatic attraction and other forms of weak adsorption. Such inhibitors include polysaccharide,humic acid and so on. Therefore,based on the structure-activity relationship between the inhibitors and Mo/ Mg sites on the basal/ edge planes of the two minerals under the actions of functional group type and number,steric configuration and other factors,the design of highly selective molecular structures by combination or grafting synthesis is one of the ideas for the development of molybdenite/ talc inhibitors. The traditional collectors of molybdenite are mainly hydrocarbon oils and sulfhydryl compounds,but there are defects of poor dispersity and poor selectivity to molybdenite and sulfide gangue minerals respectively. Therefore,on the basis of hydrocarbon oil collector, from the perspective of the chemical interaction between collector molecules and the exposed sites on the edge planes,oxidation components and dissolved components,designing highly selective collectors containing N,P,S and other elements to achieve selective collecting of the fine-grained molybdenite with severe surface oxidation and dissolution is one of the development directions of molybdenite collector molecules. Inhibitors and molybdenite collectors are the keys to the separation of molybdenite and talc. It is of great significance to design green and efficient new reagents for the development of molybdenite.

Research Progress on Enrichment and Extraction of Germanium Resources from Sphalerite in China

ZHANG Shengdong, YANG Bo, XIE Weiyou, TONG Xiong, XIE Xian

2024, 53(2):  69. 

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Germanium is a kind of strategic rare metal,which plays an important role in modern industry. As the main carrier mineral of germanium,sphalerite is an important source of germanium extraction and recovery in industry. The extraction of germanium from sphalerite plays an important role in germanium resource development. In this paper,the enrichment and extraction technology of germanium resources in sphalerite is summarized and the research and industrial practice of which in recent years are systematically introduced from several aspects:occurrence state of germanium in sphalerite,flotation theory, process and reagent research of germanium-bearing sphalerite,migration and enrichment rule of germanium in zinc sulfide smelting,method and process of recovering germanium from smelting germanium enrichment. The germanium in sphalerite mainly exists in the form of endoplasmic isomorphism,which leads to the decrease of activity of copper activation and xanthate collection,and the difficulty of flotation. The industrial practice shows that the recovery of germanium in zinc sulfide concentrate can be improved to some extent by optimizing the flotation reagents and processes of the carrier mineral "sphalerite". In the common smelting process of zinc sulfide,the main germanium-containing concentrates formed are vacuum slag,leaching slag,zinc oxide dust,germanium iron slag,neutralization slag,replacement slag,etc. For the above germanium-containing enrichment, the germanium deep enrichment extraction technology based on fire enrichment,leaching,precipitation,extraction and ion exchange has been formed,among which leaching-precipitation/ solvent extraction is the most mature in development and application. Based on the analysis of the development status,it is suggested that the enrichment and extraction technology of germanium resources in sphalerite should be further developed from three aspects:improving the recovery index of germanium at the sorting stage,improving the smelting process to enhance the enrichment degree of germanium in smelting products,and strengthening the development and industrial application of germanium extraction technology.

Shear Mechanical Properties and Parameter Analysis of Backfill-boundary Medium Combination

LU Hongjian, MOU Chao, WU Jie

2024, 53(2):  80. 

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The shear mechanical properties and parameters of the interface between backfill and boundary medium are the basic data for studying the stress distribution of backfill stope and evaluating the stability of backfill exposure. Through the combination of indoor direct shear test and RFPA3D numerical simulation test,the backfill-boundary medium combination (backfill-surrounding rock,backfill-ore body,cemented backfill-unconsolidated backfill) with three cement-sand ratios (1 ∶4, 1∶8 and 1∶20) and four contact surface normal stresses (50 kPa,100 kPa,150 kPa and 200 kPa) is studied. The results show that:with the decrease of the ratio of lime to sand,the peak shear strength of the backfill-surrounding rock combination decreases, and the failure mode changes from brittleness to ductility,and the failure mode changes from particle adhesion and block adhesion to the tip of the convex body and is cut. When the cement-sand ratio is 1∶4,the shear stress decreases vertically,and the ringing count rate suddenly increases,while the ringing count rate is relatively small at other stages. From the crack compaction stage to the failure stage,the acoustic emission ringing count rate is dense,and there is obvious dilatancy deformation in the shearing process. The peak shear strength of the interface between filling body and boundary medium decreases with the decrease of normal stress and lime-sand ratio. The peak shear strength of cemented backfill-surrounding rock interface is slightly less than that of cemented backfill-ore body,and the peak strength of cemented-non-cemented backfill combination is far less than that of ore-rock combination,which is close to the strength of non-cemented backfill itself. The cohesion and internal friction angle of the interface between the filling body and the boundary medium combination decrease with the decrease of the ra-tio of lime and sand. The cohesion and internal friction angle of backfill-surrounding rock and backfill-ore body are close,but the parameters of cohesion and internal friction angle of cemented-unconsolidated backfill are much smaller than those of cemented- ore-rock combination. The research results expand the acquisition method of shear mechanical properties of backfillboundary medium combination,and provide basic data for stability analysis of backfill stope.

Elastoplastic Solution for Surrounding Rock of Circular Roadway Based on Z-P Criterion by Considering Softening and Dilatancy

JING Laiwang, XIE Jinxin, SHANG Jiale, FENG Yuteng, JIANG Haojie, JING Wei

2024, 53(2):  88. 

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The softening and dilatancy behaviour exhibited by the stresses on the surrounding rock of the roadway has a significant impact on the deformation and breaking of the roadway ring. In order to study the influence of softening and dilatancy characteristics on the stability of the rock surrounding the roadway. According to the softening characteristics of the rock mass,an ideal elastic softening model is established and the surrounding rock is divided into the elastic zone,the plastic softening zone and the fracture zone. Based on the Z-P criterion and the non-associative flow law,the elastic-plastic analytical solution for circular roadways with intermediate principal stresses is derived by considering the softening and dilatancy characteristics of the surrounding rock. The Z-P criterion is compared with the M-C and D-P criteria,the influence of softening modulus, dilatancy and other factors on the roadway surrounding rock is analysed. The results show that the Z-P criterion is well suited to the softening and dilatancy of the roadway. At an intermediate principal stress factor of 0. 4,the plastic zone of the surrounding rock is the smallest,the displacement of the surrounding rock is the smallest,and the stress in the plastic zone is the largest. The larger the softening modulus,the larger the radius of the fracture zone of the surrounding rock. The larger the shear expansion angle,the larger the displacement of the plastic zone and the larger the radius of the fracture zone. The stronger the support resistance,the smaller the plastic zone of the roadway,and increasing the support resistance can effectively control the deformation of the roadway surrounding rock.

Study on Early Mechanical Strength Characteristics and Toughening Mechanism of Polypropylene Fiber-Phosphogypsum Cement

ZHANG Weizhong, ZHOU Kai, KONG Dehua, WU Qianqian, KANG Qinrong, PAN Deng

2024, 53(2):  97. 

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In the research field of traditional cementitious composites,fibers enhance the strength,toughness,ductility and crack resistance of the materials. In order to improve the early strength of phosphogypsum cements,polypropylene fibers were doped as reinforcing agent,and fiber-doped phosphogypsum cements preparation test and uniaxial compressive strength test were carried out to analyze the effect of fibers on the damage law of phosphogypsum cements,and the toughening mechanism of fibers on phosphogypsum cements was investigated by SEM. The results show that:the uniaxial compressive strength of phosphogypsum cementum increased with the fiber dosage,the uniaxial compressive strength of phosphogypsum cementum showed a tendency to increase and then decrease,and the optimal dosage of fibers is 1%;the phosphogypsum cementum doped with fibers can delay the time of reaching the peak compressive strength and the peak stress is greater in destruction;the phosphogypsum cementum without doped fibers is rapidly destabilized after the load exceeded the peak stress,and the phosphogypsum cementum with doped polypropylene fibers showed a slow decrease in the trend;with the fiber dosage,the phosphogypsum cementum is slowly stabilized and the peak stress is reduced. With the incorporation of fibers,the number of cracks in the phosphogypsum cement gradually decreases,and the cracks are continuous,and the ductile deformation of the phosphogypsum cement is obvious;under the microscopic surface of polypropylene fibers,there are flocculated hydration products attached to the surface of the polypropylene fibers,and in the process of slurry solidification to form the mesh structure with mutual adhesive connection. The research results of this paper can provide certain reference for the application of phosphogypsum-based composites in solid waste cementation and filling site.

Damage Evolution of Coal Cylinder under Uniform Confinement of Carbon Fiber Sheets

LI Qingwen, GAO Anliang, YU Mengmeng, GAO Senlin, XU Kangkang, LI Ying, HUANG Xiao

2024, 53(2):  104. 

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The coal pillar instability disaster is still one of the hot research issues in the safe and efficient mining of coal resources. In order to further study the influence of carbon fiber sheets layers and loading rates on the energy evolution of coal cylinder. The loading rate is divided into four levels:0. 01 mm/ min,0. 1 mm/ min,1 mm/ min and 10 mm/ min,and the layers number of carbon fiber sheets is divided into three categories:0 layer,1 layer and 2 layers. The SAM-2000 rock comprehensive test system was used to perform uniaxial axial compression test on coal cylinder. The test results show that under the same layers of carbon fiber sheets,the higher the loading rate,the more obvious the diffusion of coal dust,the worse the integrity of the coal cylinder,and the stronger the energy release,which belongs to the split-shear composite failure mode. the more layers of carbon fiber sheets,the total energy,elastic energy and dissipated energy at peak gradually increase,the effect of loading rate on the energy of coal cylinder is reduced. According to the energy dissipation theory,the damage factor is proposed,and then the constitutive model is established,and it has a high degree of fitting with the experimental verification.

Stress Intensity Factor of Rock Mass Offset Oblique Crack under Three-Point Bending Load

WANG Chao, WU Yongping, ZHAO Zihao, CAO Jian, DUAN Huiqiang, YANG Panpan

2024, 53(2):  114. 

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The roof of underground roadway (chambers) often breaks due to bending and delamination,and the location of the break is closely related to the geometric shape and position of the cracks. To reveal the impact of cracks on rock fracture, a three-point bending model of rock mass with offset oblique cracks was established. The offset coefficient and connectivity ratio of cracks were defined,and the relationship between the offset coefficient,inclination angle,and connectivity of cracks was analyzed. Based on the principle of mechanical equilibrium and the σ-K relationship derives the stress intensity factor K correlation between offset oblique cracks and offset vertical cracks. At the same time,the influence of crack inclination angle,connectivity, and offset coefficient on the stress intensity factor was analyzed. This method can provide a judgment basis for the tensile fracture of the roof of the roadway (chamber) under the influence of cracks.

Study on the Conventional State-type Peridynamics Model Considering Shear Deformation and the Evolution Law of Rock Fracture Propagation

FENG Qiang, XU Longwei, LIU Weiwei, ZHAO Zidong, SUN Shangqu, ZHANG Qiang

2024, 53(2):  123. 

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The complex fracture structure in rock mass seriously affects the stability and failure mode of engineering rock mass. It is of great theoretical significance and engineering value to study its influence on the damage and failure mode of fractured rock mass. An improved OSB-PD model considering shear deformation is constructed based on the conventional state-type peridynamics ( OSB-PD ) theory,and the crack propagation evolution law of fractured rock mass under uniaxial compression is studied based on the constructed OSB-PD model considering shear deformation. A new simulation method of rock heterogeneity is proposed,and the influence of rock heterogeneity on the crack propagation behavior of rock under different prefabricated crack angles is studied. The results show that the prefabricated crack angle has a great influence on the crack propagation of fractured rock,and the heterogeneity of rock will greatly increase the crack propagation speed.

Mechanical Properties and Meso-damage Law of Fractured Mudstone under Freeze-thaw Cycles

ZHANG Ying, DING Zhaoyang

2024, 53(2):  131. 

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The freeze-thaw cycle is one of the important environmental factors that accelerate the deterioration of rock material properties,and it is also an important hidden danger that affects the stability and safety of open-pit slope. In order to study the mechanical strength attenuation characteristics and damage effects of fractured mudstone under freeze-thaw cycles,uniaxial compression tests and computed tomography (CT) scanning tests were carried out on mudstone samples after 0,5,10, 20 and 50 freeze-thaw cycles respectively. At the same time,the microscopic damage mechanism of mudstone was studied by scanning electron microscopy. The experimental results show that the uniaxial compressive strength and elastic modulus of mudstone decrease gradually with the increase of the number of freeze-thaw cycles,and the decay rate is most significant at 0~10 freeze-thaw cycles,and then the decay rate gradually slows down. Two-dimensional CT images show that the pore structure of mudstone samples is continuously developed due to freeze-thaw cycles,and the porosity has an exponential and negative linear correlation with cycle times and elastic modulus,respectively. This phenomenon indicates that the accumulation of damage to mudstone mesostructure is significantly correlated with the attenuation degree of macroscopic mechanical properties. Under the action of freeze-thaw cycle,the damage degree of the internal microstructure of fractured mudstone is gradually deepened,and the expansion of cracks and the change of particle contact relationship are the important factors leading to the decline of mudstone strength. The above analysis has a certain reference significance for the design and construction of the open-pit slope in the fractured mudstone distribution area.

Numerical Simulation of Shale Fracturing under the Coupling of Laminar Dip and Size Effect

YAN Xulong, WU Zhonghu, LAN Baofeng, JIANG Haishen, YU Jun, YANG Xianchao

2024, 53(2):  137. 

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To study the effects of different sizes of shale with the same material and different dips of laminae on its mechanical properties and damage characteristics,in order to provide important theoretical guidance for the shale gas extraction from the Lower Cambrian brown shale under hydraulic fracturing in Fenggang Three Areas of Qianbei Region. The shale model was constructed based on RFPA2D-Flow software,and the controlled perimeter pressure was 10MPa,the water pressure was 8MPa,and the quartz content was fixed at 40%. Four sets of aspect ratios of 1,2,3 and 4 were set,and the inclination angles of different layers in each set were 0°,30°,60° and 90°. The total number of experimental groups was 16,and the effects of laminar inclination angle and size effect on the stress-strain curve characteristics,peak strength,deformation characteristics,and damage characteristics of shale were analyzed. The study shows that the elastic modulus and peak strength of shale matrix have the size effect,and the elastic modulus and peak strength of shale are significantly affected by the angle of inclination of the laminae,and both show obvious anisotropy. Under the same aspect ratio,the compressive strength shows a "V" curve with the increase of laminar inclination. Based on the crack distribution of specimens with different laminar inclination angles and aspect ratios,the damage modes can be categorized into three types,i. e. ,Ⅰ-type,polyflexural,and flame-type damage,and Ⅰ-type damage modes dominate in all models. Tensile damage mainly occurs at aspect ratios of 1,3,and 4,accompanied by a small amount of shear damage,indicating that the specimen is characterized by compressive but not tensile resistance,and at an aspect ratio of 2,tensile damage is balanced with shear damage,indicating that the specimen is neither compressive nor tensile.

Analysis of Crack Expansion Pattern after Corrosion of Fractured Sandstone Based on Particle Flow

KANG Zhiqiang, WANG Zhilei, 　FENG Jiangjiang, XIN Dongfu, YAO Xulong

2024, 53(2):  144. 

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Biaxial compression tests based on particle flow discrete element method were conducted on sandstone with prefabricated cracks after corrosion to analyze the crack initiation,extension and penetration damage laws of fractured rocks after different chemical corrosion,and the experimental phenomena were analyzed using particle flow PFC2D simulations to explain. The results show that:the change characteristics of the stress-strain curve of the fractured sandstone after solution corrosion under biaxial loading with different loaded side pressures with the higher side pressure loading,the higher the peak strength. The angle of wing-shaped cracks sprouting under different chemical solution corrosion changes to different degrees, and the number and angle of wing-shaped cracks and shear cracks sprouting will produce obvious changes,among which hydrochloric acid solution causes the greatest degree of damage to the rock. Considering chemical corrosion and mechanical properties together,a numerical model of the fractured rock can be established to further analyze its behavior under different environments. This is important for understanding the stability of rocks and for applications in geoengineering.

Experimental Study on Hydrogen-based Mineral Phase Transformation Followed by Magnetic Separation of Iron Ore from Shilu,Hainan

GUO Fengfang, HAN Yuexin, ZHANG Qi, GAO Peng, HE Jiahao

2024, 53(2):  152. 

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The iron content of the Shilu iron ore in Hainan province is 52. 45%. Within this composition,a substantial 86. 18% manifests as hematite/ limonite,with a minor presence of magnetite. To efficiently recover this ore,a systematic experimental study on Hydrogen-based Mineral Phase Transformation (HMPT)-magnetic separation process was carried out,and the products under the optimal conditions were analyzed by chemical composition,XRD and VSM. The results indicate that,under the optimal conditions of a feed particle size of -0. 074 mm accounting for 89. 41%,HMPT temperature of 525 ℃,HMPT time of 10 min,total gas flow rate of 500 mL/ min,H2 concentration of 20%,and HMPT product grinding fineness of -0. 045 mm accounting for 69. 68%,the iron concentrate with an iron grade of 65. 26% and an iron recovery rate of 95. 39% was obtained by magnetic separation. The iron concentrate obtained from the experiments exhibited an increase of 2. 7 percentage points in iron grade and a commendable 30 percentage point rise in iron recovery rate compared to the original gravity and magnetic separation combined process. The study not only provides technical support for the industrial application of HMPT-efficient sorting in Hainan Shilu iron ore,but also opens up new avenues for the green and efficient sorting of other complex and refractory iron ore resources.

Effect and Mechanism of Sodium Hypochlorite Strengthening Sulfuration Flotation of Cuprite

MA Yingqiang, YU Xiangzhou, LUO Jin, SONG Zhenguo, YIN Wanzhong, RAO Feng

2024, 53(2):  157. 

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Moderate surface oxidation can improve the effect of sulfuration flotation of cuprite. The effect of sodium hypochlorite on sulfuration flotation of cuprite was investigated by single mineral flotation test,and the mechanism of sodium hypochlorite enhanced sulfuration flotation of cuprite was discussed by means of X-ray photoelectron spectroscopy and mineral surface Zeta potential measurement. The results show that compared with direct sulfuration flotation,sodium hypochlorite can increase the sulfuration flotation recovery rate of copper by 8. 95 percentage points,and sodium hypochlorite can promote the oxidation of Cu(Ⅰ) component on the surface of copper to Cu(Ⅱ) component,which can enhance the reactivity of copper component and sulfuration agent,and strengthen the sulfuration effect of copper. It can promote the sulfide flotation of cuprite.

Study on the Oxidation of Pyrite and Its Effect on Mineral Floatability

CHEN Yu, DAI Shujuan, LI Hongxiang, LI Pengcheng, YUAN Linsong

2024, 53(2):  163. 

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Pyrite is commonly found in non-ferrous sulfide ores. Pyrite is prone to oxidation,and after oxidation,the physical and chemical properties of the mineral surface change,which in turn affects the floatability of the mineral. Using oxidation tests,flotation tests,and detection analysis,study the oxidation characteristics of pyrite and the impact of oxidation on its floatability. The results of single mineral oxidation tests show that the degree of oxidation of pyrite in air,water,hydrogen peroxide or potassium permanganate aqueous solutions gradually increases with time. The degree of oxidation of minerals in hydrogen peroxide and potassium permanganate aqueous solutions is greater than in water and air;The flotation test results before and after single mineral oxidation show that the recovery rate of pyrite increases and decreases after oxidation in air,water,and hydrogen peroxide aqueous solutions,and decreases after oxidation in potassium permanganate aqueous solution;The flotation test results of the artificial mixed ore of pyrite and quartz (with quartz accounting for 1/3) are similar to the conclusions of the single mineral test;The oxidation mechanism of pyrite and its interaction with butyl xanthate were studied using infrared spectroscopy (FTIR),Zeta potential,and X-ray photoelectron spectroscopy (XPS). The mechanism analysis results showed that butyl xanthate produced chemical adsorption on the surface of pyrite. After oxidation,the zero point of pyrite shifted towards the direction with lower potential,and after interaction with butyl xanthate,the zero point shifted slightly. Both iron and sulfur in pyrite underwent oxidation. The experimental research results can provide reference for regulating the floatability of pyrite and improving the flotation process of pyrite containing ores.

Experimental Study on Separation of Ultra-fine Copper-Molybdenum Bulk Concentrate by Pulsating High Gradient Magnetic Separation

YANG Kangning, ZENG Jianwu, YANG Jing, HUANG Huichun, XIE Jincheng, SHAO Yanhai, CHEN Luzheng

2024, 53(2):  171. 

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Chalcopyrite is paramagnetic and molybdenite is diamagnetic,and thus they are separatable through high gradient magnetic separation. A SLon-100 periodic pulsating high gradient magnetic separator was used to separate a roughing concentrate of chalcopyrite-molybdenite co-flotation from Jinduicheng Molybdenum Industry, which assays 14. 42% Cu and 12. 40% Mo,with -0. 019 mm ultra-fine fraction weighting 83. 80%. The results showed that under the conditions of a pulsating stroke of 5 mm,a pulsating frequency of 150 r/ min,a rod diameter of 1. 5 mm in matrix,a slurry flow rate of 2. 0 cm/ s,a roughing magnetic induction of 1. 6 T and a scavenging magnetic induction of 1. 7 T,a copper concentrate with a yield of 48. 64%,Cu grade of 22. 82%,Mo grade of 4. 40%,and Cu recovery of 77. 82% and a molybdenum concentrate with a yield of 51. 36%,Cu grade of 6. 16%,Mo grade of 19. 96%,and Mo recovery of 82. 73% were respectively obtained via one roughing and one scavenging pulsating high gradient magnetic separation process. This effective separation for the ultra-fine chalcopyritemolybdenite concentrate demonstrated the availability of pulsating high gradient magnetic separation technology for separating the ultra-fine copper-molybdenum concentrate,providing a valuable reference for the environment-friendly separation of similar copper-molybdenum bulk concentrates.

A Review of Development of Mineral Surface Liberation Analysis Technology

KANG He, LI Chao, YE Xiaolu, LI Guosheng, CAO Yijun

2024, 53(2):  177. 

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The degree of mineral liberation has a significant effect on the separation efficiency of flotation,and accurate analysis of the mineral liberation behavior on the particle surface is a prerequisite for efficient control of the flotation process. We summarized the common methods of mineral surface liberation analysis in the field of mineral processing:2D liberation analysis based on scanning electron microscopy (SEM),stereoscopic correction of 2D liberation and 3D liberation analysis methods (X-ray micro tomography). When the 2D liberation analysis method is applied to low liberation coarse composite particle, there is a stereological bias,and the 2D mineral liberation stereological correction of complex associated particles still faces challenges. 2D liberation analysis are suitable for individual or highly liberated particles by traditional flotation,while for coarse particles with low mineral liberation,3D liberation analysis can provide more accurate physical property analysis results without stereological bias.

Study on Process Mineralogy of a Foreign Associated Natural Copper-iron Ore

LUO Hongzhen, ZHANG Lin, XU Jian, YANG Hanxu, SAI Mingyu

2024, 53(2):  183. 

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In order to provide a theoretical basis for the beneficiation process research of a foreign associated natural copper- iron ore,a detailed process mineralogy study was carried out by using mineral liberation analyser (MLA),combined with chemical analysis,optical microscopy,XRD and other analytical methods. The results show that the ore grade of Cu is 1. 06%, the grade of Fe is 44. 91%,and the Cu mainly exists in the form of natural Cu with a distribution rate of 66. 98%,while the Fe mainly exists in the form of magnetite and hematite-limonite with a distribution rate of 41. 26% and 45. 05%,respectively. The ore structure mainly consists of disseminated structures,layered structures,and block structures,and the main mineral structure is porphyry structure,network structure,granular structure,closed structure and residual structure. The ore contains a large variety of minerals,and the minerals that can be comprehensively recycled are magnetite,natural copper and copper sulfide minerals. The natural copper in the ore is closely symbiotic with limonite,and the chalcopyrite (chalcocite) is closely symbiotic with the gangue and pyrrhotite;the porphyritic magnetite in the ore closely symbiotic with martite and limonite. Natural copper, chalcopyrite and chalcopyrite assemblages are mainly in the form of microfine grains,-60 μm particle size distribution rate of 82. 24% and 86. 15%;iron minerals embedded in the particle size from coarse to fine:dlimonite >dmagnetite >dhematite,all three are mainly in the form of fine grains,-100 μm particle size distribution rate of 56. 57%,69. 87% and 82. 31%,respectively,The ore needs to be ground to below 60 μm in order to dissociate most of the copper and iron minerals. Limonite in the ore is easy to sludge in the milling and flotation process,which will deteriorate the index of copper minerals separation. Therefore,based on the recovery of only copper sulfide and natural copper,the theoretical copper recovery is 81. 01%. The recommended beneficiation process is raw ore grinding-copper and sulfur mixed flotation-mixed flotation tailings magnetic separation to recover magne-tite-mixed flotation concentrate gravity separation and flotation combined to recover copper minerals.

Research on Power Frequency Noise Suppression of AMT in Laochang Ag-Pb-Zn Polymetallic Deposit, Lancang County,Yunnan Province

LI Kexuan, LIU Huipeng, LI Bo

2024, 53(2):  189. 

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Laochang Ag-Pb-Zn polymetallic deposit in Lanchang,Yunnan Province is a typical deposit in the "Sanjiang" area of southwest China,which is facing a resource crisis recently. The audio-frequency magnetotellurics(AMT) has been carried out in the margin exploration of this deposit,but the frequency distortion of some measurement points is caused by the interference of high voltage lines. To deal with this problem,a method is proposed for suppressing industrial frequency noise based on isolated frequency point extraction and magnetic field data reconstruction technology. By setting a limit to distinguish all measurement points,it can quickly distinguish the measurement points with different degrees of industrial frequency interference; then the data extraction is carried out by avoiding the interfered 50 Hz and multiples frequency band data;For the measurement points with strong industrial frequency interference that cannot be avoided,the magnetic field data reconstruction is carried out by using the inverse distance weighted for the strong interfered measurement points using the data of their nearby measurement points. The AMT data of the Laochang Ag-Pb-Zn polymetallic deposit in Lancang was processed by the above method,which effectively avoided the 50 Hz and odd times harmonic interference,achieved a relatively good noise suppression effect,and circled two low-resistance anomalous areas with ore finding potential,which provided a direction for ore finding exploration at the side of the mine. The method also provides a new solution to the industrial frequency interference in geophysical exploration work.

Dynamic Estimation Method of River Embankment Filling of Concurrent Mining and Reclamation in Subsidence Area

LI Sihao, ZHA Jianfeng, GUAN Jie, ZHANG Min

2024, 53(2):  198. 

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The deformation and destruction of river embankment caused by coal mining significantly reduce its flood control safety performance. The traditional treatment method of " first destroy and then treat" has the problems of delayed repair and heavy flood control pressure,which has great potential safety hazards and even induces dam break,flood and other major public safety accidents. The main technical way to solve this problem is to restore the flood control capacity of the river embankment in time while mining. Based on the dynamic process characteristics of mining subsidence,this paper presents the design process of concurrent mining and reclamation of the river embankment in subsidence areas;the calculation model of dynamic fill volume in the process of river embankment treatment is constructed and applied to a treatment project about the river embankment suffered the mining damage. The results show that the risk of river overflow in the process of mining can be reduced, and the damage degree of the river embankment caused by mining damage can be alleviated by using the method of concurrent mining and reclamation to restore the river embankment in the subsidence area;the proposed method of dynamic fill volume prediction can accurately predict the earthwork volume in each treatment stage of embankment treatment,meet the actual engineering needs,and provide a basis for the design of embankment treatment engineering.

Improved BP Neural Network Model for Surface Subsidence Prediction

JIANG Yan, LIAN Han, XI Donghe

2024, 53(2):  205. 

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In order to predict surface subsidence deformation more accurately,a multi network collaborative calculation strategy was adopted based on the Adaboost algorithm to improve the BP neural network. The improved neural network was trained on actual subsidence data to predict the maximum subsidence,influence angle tangent,and inflection point offset. The three predicted parameters were introduced into the probability integration method,and a surface subsidence formula was established. The improvement effect and surface subsidence formula were verified separately. The study results show that:① By comparing the calculation accuracy of the BP neural network before and after improvement,the results showed that the error of the BP neural network without Adaboost algorithm improvement it is obviously greater than the improved BP neural network,indicating that the calculation accuracy of the BP neural network based on Adaboost correction has been effectively improved; ② Based on the BP neural network,the maximum subsidence,influence angle tangent,and inflection point offset are predicted. Combined with probability analysis method,the description of surface subsidence above the main section of the goaf after stable subsidence can be achieved. Taking the surface of the 3301 goaf in a certain mine in Southwestern Shandong Province as the study example,the improved BP neural network is used to predict the maximum subsidence,influence angle tangent,and inflection point offset,and then the surface subsidence curve is given. Compared with the on-site measurement results,the comparison results show that the maximum error of the improved BP neural network is less than 0. 105 m,and the maximum relative error is 4. 3%,which proves the reliability of the calculation method in this paper.

Path Planning Algorithm of Mine Inspection Robot Based on Deep Reinforcement Learning and Large Neighborhood Search

BIAN Yanhua, XIE Lu, MIAO Chao

2024, 53(2):  212. 

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At present,most mine inspection robots use LiDAR as the detection method of mine environment,which is not obvious for some small target objects and objects with small albedo,and is easy to cause false detection or missing detection,resulting in mine safety accidents. In order to improve the recognition accuracy of the mine inspection robot,the path planning method based on reinforcement learning combined with large neighborhood search was introduced into the path planning work of the mine inspection robot to improve the scene perception ability of the mine inspection robot. Firstly,a sequential path planning model based on LSTM is proposed,which can extract image features from the RGB camera of the robot and carry out scene perception through deep learning. Secondly,the information collected by the LiDAR equipment is processed,and the large neighborhood search algorithm is used to find multiple optimal paths in the space for the navigation of the subsequent scene. Finally, deep reinforcement learning and large neighborhood search methods are used to achieve accurate navigation of mine inspection robots,and the best inspection path is selected. In order to verify the performance of the proposed algorithm,scene construction,navigation simulation,model training and testing are carried out in 2D and 3D space. The results show that this method has better capability of path planning in simulated environment and real scene.

Software Development for Grouping Joints Based on Improved Fuzzy Algorithm

GUO Yining, LIU Tiexin, DONG Ziyan, ZHENG Hongchun, HAN Ju, ZHAN Bixiong

2024, 53(2):  219. 

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Joints are widely present in rock masses,and their development affects the stability and seepage characteristics of the rock masses. Due to the large number of joints,grouping is currently required for their study. Traditional grouping methods, such as relying on rose diagrams and density maps such as poles,cannot determine the specific data of each group of joints and have limited effect on grouping of discrete points. The contemporary clustering algorithm using machine learning also suffers from the deficiency that the number of clusters selected affects the grouping effect. In view of this,a joints' orientation clustering program (JOCP) based on an improved fuzzy clustering algorithm was developed on the MATLAB platform. JOCP takes the original coordinate data and the target number of clusters as the input,and the nodal yield data,the cluster centers,the distribution of clustering results and the validity index as the output. The program is used in the analysis of a thousand slope nodal data in Dalian,and the results prove that the program can improve the grouping certainty and achieve the objective and accurate grouping effect. This program can provide technical support for geological exploration,disaster prediction and other fields.

Simulation of Three Product Magnetic Separation Column Process Simulation Based on FEM,CFD and DEM Coupling

WU Junjie, YUE Xiang, GUO Xiaofei, DAI Shujuan, ZHANG Mingrui, REN Weijie

2024, 53(2):  225. 

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In order to find out the movement law and influencing factors of magnetite particles in the three-product magnetic separation column,the magnetic separation process was simulated by FEM,CFD and DEM coupling method,and verified by the actual separation test. Based on the particle size distribution,mineral composition,magnetization characteristics and mechanical properties of magnetite,the overlapping sphere particle model of magnetite was established. ANSYS software was used to simulate the magnetic field distribution of three-product magnetic separation column. Fluent software was used to simulate the flow field distribution of the three-product magnetic separation column. EDEM-API was used to realize the coupling of ore particles,pulsating magnetic field and flow field in the discrete element software EDEM. The effects of magnetic induction intensity, excitation period and rising water flow rate of the three-product magnetic separation column on the separation process were simulated. When the TFe grade of the ore is 61. 42%,the TFe grades of the concentrate,the middle ore and the tailings obtained by the simulation test are 63. 60%,58. 44% and 29. 63%,respectively. The separation test was carried out by using ϕ159 three-product magnetic separation column under the same simulation conditions. The results show that the TFe grade of concentrate,middle ore and tailings is 65. 55%,42. 58% and 24. 23% respectively,and the relative error between the simulation test and the actual test is less than 3%.

Research on the Development Law of Rock Movement in the Opencast Underground Combined Mining of Dahongshan Iron Mine

ZHANG Wei, YANG Tianhong, HOU Junxu, MA Kai

2024, 53(2):  232. 

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The surface movement caused by underground mining can affect the stability of adjacent open-pit slopes. Taking the combined open-pit and underground mining of Dahongshan Iron Mine as an example,various methods such as microseismic observation and surface cracking observation were used for rock movement monitoring and data analysis to explore the laws of rock mass movement and surface cracking caused by underground mining. Firstly,the historical monitoring data of the open-pit underground combined mining project was organized and analyzed,including the development of surface subsidence and cracks. Secondly,based on the deformation characteristics of surrounding rock during underground mining,microseismic monitoring was conducted to obtain information on rock damage and failure. At the same time,based on the geological conditions of the mine and statistical data,the range of changes in subsidence angle is determined. The results indicate that the development stages of rock mass movement in the open-pit underground joint mining of Dahongshan Iron Mine can be divided into: movement stages of caving and surface connectivity,fully developed rock movement stages of subsidence areas,asymmetric development stages of subsidence angles influenced by F2 fault,and rock movement stages under waste rock filling and deep mining. The development range of the northwest subsidence angle is 75°~81°,and the southeast subsidence angle is 65°~82°. The study can provide a certain reference for the analysis of the development law of rock movement in mines under similar geological and engineering conditions.

Analysis of the Influence of Deep Mining on the Stability of Surface and Shaft

MA Hongwei, LI Ming, ZHANG Lili, WANG Zhixiu, LIU Xiaoyu

2024, 53(2):  239. 

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Taking the deep mine Fushan Gold Mine as the engineering background,the 3D numerical analysis and modeling software 3DMine-FLAC3D was used to analyze the ore body displacement pattern and the influence of deep mining on the surface,and a 3D numerical calculation model of the integrated mine area in Fushan was established. The analysis was carried out for the effects of ore body displacement and surface deformation. The results show that:① The bottom drumming occurs at the lower plate of the ore body to different degrees due to the unloading effect of excavation,and the deformation of the upper plate of the ore body is characterized by sinking,and the further away from the ore body,the smaller the deformation of the surrounding rock. ② After the stoping and filling of the designed ore body,the maximum settlement deformation,tilt deformation, curvature and horizontal deformation of the surface can meet the relevant requirements of the ′ Nonferrous Metal Mining Design Specification ′ (GB 50771-2012). ③ The relative deformation at the center line of the main shaft and the 207 air shaft is small,and the mining activities of the underground ore body have no effect on the main shaft and the 207 air shaft. ④ The surface subsidence monitoring shows that the surface subsidence displacement caused by underground mining is very small.

Research on Plane Boundary Detection of Goaf Based on High Precision Magnetic Survey Method

GU Pengyu, YAO Yuzeng, JIA Sanshi, CHENG Hao, YAN Di

2024, 53(2):  247. 

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The spatial location,scale,and geological environment of the mining goaves are variant,and the methodologies of detection and data processing are also different,while the planar boundaries of the mining goaf have always been the difficulty in the detection of the mining area. A ground-based high-precision magnetic survey was carried out in a typical area of the manganese-fluorite mining area in Sunit Right Banner,Inner Mongolia and the planar boundary of the mining goaf was delineated according to the magnetic anomaly and verified by drilling. The results show that:① The residual roof and footwall ore beds and manganese mineralized alteration wall-rocks exhibit obvious high magnetic anomalies,while the area of goaf is low,i. e. , the low magnetic anomalies enclosed in the high anomalies are good indicators of goaves,and the boundary of low magnetic anomalies basically reflects the planar boundary of the goaf. ② Based on the accurate delineation of the planar boundary of the mining goaf,the vertical depth of the mining goaf can be determined by the multi-electrode resistivity method and geo-radar, which can greatly improve the detection efficiency of the mining goaves. The research is not only of great significance to the detection and management of the mining gloves in the later stage of the Sunit mining area,but also provides a useful reference for the goaf-detection in other similar mining districts.

Study on the Strength of Granite Slope Rock Mass under Freeze-thaw Cycles

LIU Hong, ZHANG Zhaofei, LI Zhaolong, DIAO Hu

2024, 53(2):  255. 

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Taking the granite slope rock mass in Yichun Luming Molybdenum Mine as an example,freeze-thaw cyclic uniaxial compressive strength tests and longitudinal wave velocity tests were conducted on granite rock samples with different degrees of weathering. It was found that the freeze-thaw cyclic uniaxial compressive strength and longitudinal wave velocity losses of granite with different degrees of weathering were different,and the freeze-thaw coefficient of granite with high degrees of weathering was lower;There is a linear relationship between the freeze-thaw coefficient of uniaxial compressive strength of granite under freeze-thaw cycle and the damage variable of p-wave wave velocity,and the linear relationship is similar for different weathering types of granite. From the perspective of slope stability analysis,two methods for obtaining the strength parameters of granite slope rock mass under freeze-thaw cycles were proposed and verified through calculation. The results showed that:using uniaxial compressive strength freeze-thaw coefficient to directly reduce shear strength,or using longitudinal wave rapid freezethaw coefficient to reduce RMR value to derive shear strength,the obtained results can be used for slope stability calculation; Relatively speaking,the Factor of safety calculated by the latter is closer to the actual stability state of the slope.

Study on Self-organized Critical Characteristics of True Rriaxial Single-face Empty Granite Rockburst

SUN Guanghua, GUO Jiang, WU Bingwei, QI Yuzhu, HAN Kaiming

2024, 53(2):  262. 

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In order to explore the instability characteristics of granite rock burst under different stress states,the true triaxial single-faced empty rock burst test was carried out. Combined with the acoustic emission monitoring system,according to the self-organized criticality theory,the stress change during the rock burst process and the time attribute of the acoustic emission energy sequence and the spatial attribute of the positioning information were analyzed. The experimental results show that the self-organizing process of rockburst is decomposed into time line and space line,which realizes the visualization of self-organizing process of rockburst and the quantification of rock mass state to the greatest extent,and the energy time domain is verified by power law characteristics,which has strong self-similarity. The critical index of the second stage of rockburst is larger than that of the first stage,indicating that the probability of rockburst increases with the evolution of self-organization. The selforganization behavior of rock burst has the effect of intermediate principal stress. With the increase of intermediate principal stress,the limiting effect on rock fracture is enhanced. The later the critical point appears,the larger the critical index is. At the same time,the quiet period from sub-critical point to critical point under high intermediate principal stress is longer,and the self-organization behavior is weaker. It is easy to induce sudden and destructive rock burst disasters,and the difficulty of prediction is increased. The results of this study provide a more advanced and perfect idea for accurately predicting rock burst.

Numerical Simulation Study on Ventilation and Cooling of Deep Mine Tunnels

LI Xiaojian, JIA Mintao, ZHAO Xu, LI Weiguo, ZHANG Mingfeng

2024, 53(2):  271. 

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Aiming at the problems such as high temperature and difficult air supply in single-head excavation in hightemperature deep mine,based on gas-solid two-phase flow theory,three-dimensional fluid simulation software was adopted to simulate the high-temperature environment in deep well. According to the distribution characteristics of temperature field and velocity field in main transportation roadway and single-head roadway under different ventilation parameters,the influence law of wind temperature,wind speed and rock temperature on the distribution characteristics of air flow and temperature distribution was studied. The results show that the critical distance for effective ventilation of single-ended roadway is 7 m,and "8" shaped eddy current will be generated at the intersection of roadway,and the average temperature at the cross section of eddy current reaches the lowest value,exceeding 7 m,and local ventilation measures should be taken to improve the working environment. When refrigeration equipment is used for cooling,the distance between the refrigeration device and the driving operation point is less than 30 m,and the inlet air supply temperature is 20 ℃ to 25 ℃. For the thermal insulation material covering a certain thickness of the surrounding rock of the high-heat roadway,the heat dissipation of the rock wall to the air flow can be reduced effectively. The research results can provide powerful theoretical support for the design of ventilation system and local cooling and cooling in high temperature deep mine.

Influences of Nickel Slag Addition on Shrinkage Behavior of Fly Ash-based Geopolymer

QI Daozheng, WANG Bingjian, CHEN Deng, LI Li

2024, 53(2):  276. 

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Nickel slag is theindustrial solid waste discharged during the nickel production. Using nickel slag as a raw material to prepare geopolymers not only reduces the carbon footprint of geopolymers,but also promotes the sustainable development of the nickel-iron alloy industry. In this paper,nickel slag wasincorporated into the fly ash-based geopolymers,and the influences of the slag addition on the shrinkage behavior of the binders were investigated. The results showed that the 25% nickel slag addition not only improved the compressive strengths of the geopolymers,but alsoreduced the autogenous shrinkage and drying shrinkage ratios. Nickel slag exhibitedrelatively lower reactivity than fly ash. The addition into fly ash-based geopolymers slowed down the kinetics of alkali-induced reaction,and consequently mitigated the self-shrinkage of the binders. On the other hand,nickel slag particles played themicro-aggregate role in the binders. The pore structure of geopolymers was compacted. It not only enhanced the compressive strengths of the binders,but also restricted the water evaporation during the drying process and consequently reduced the drying shrinkage.