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    15 April 2024, Volume 53 Issue 4
    Previous Issue   
    Study on Physical Simulation Experiment of Ore Residue Morphology by Caving Method
    SONG Delin, WANG Chunwang, LI Shaopu, ZHANG Hao
    2024, 53(4):  0. 
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    The pillarless sublevel caving method is widely used in the mining of underground metal deposits. Large loss and dilution is one of its main problems. The existence of ore remant has a great influence on the ore drawing effect,which directly affects the loss and dilution in the mining process. In order to obtain a good mining index,it is necessary to study the composition,spatial location and morphology of the ore remnant. In view of the lack of complete disclosure means in the current research on the ore remnant,firstly,based on liquid injection cementation,a method for completely exposing the ore remnant inside the ore body after ore drawing is proposed. Secondly,the physical model drawing experiment of pillarless sublevel caving method with vertical approach arrangement is carried out. The ore remnant is completely exposed by the proposed method and three-dimensional modeling is carried out by three-dimensional scanner. On this basis,the composition,spatial position and shape of the ore remnant are revealed. At the same time,the variation law of the mixed part of ore and rock and the ore remnant on the wall with drawing is studied. The proposed method makes up for the deficiency of the traditional ore drawing simulation experiment. On this basis,the characteristics and laws of the ore remnant are revealed,which is more conducive to guiding the formulation of mining measures.
    Research and Practice on Safe Mining Technology of Hanging Wall Ore in Deep Open-pit Mine
    LI De, LI Cui, LIU Lei, SUN Mingzhi, QIN Lujun
    2024, 53(4):  7. 
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    In order to fully recover the hanging wall ore resources,according to the occurrence conditions of hanging wall ore in a deep open pit mine in Panxi and the situation of internal dumping,this paper puts forward the technology of "continuous backfilling of internal dumping and step-by-step mining of hanging wall ore". The temporary road is built to the wide platform by using the inner dump to create the equipment operation space for the mining work. At the same time,the continuous backfilling of the mining pit shortens the exposure time of the slope after the mining of the hanging wall ore. The pre-splitting blasting is used to control the single sound initiation charge below 250 kg,and the equivalent load is loaded in the mining area. After calculation,the maximum vibration speed of the slope is 1. 6 cm/ s,which meets the safety speed requirements of the slope. The three-dimensional model of the slope is established,and the change of the slope displacement in the whole process of the mining process is calculated. After the completion of the mining,the overall displacement of the slope is less than 0. 5 cm, and there will be no large-scale slope instability. The field application shows that the cumulative output of ore is more than 583. 4 thousand tons,and the slope is stable. It provides technical support for the next step of comprehensive mining of hanging wall ore resources,which can be used for reference by similar mines.
    Study on Early Strength Characteristics of Cemented Backfill Considering Curing Conditions of Pressure and Temperature
    JIA Chong, ZHAO Yue, GUO Lijie, LIU Guangsheng, PENG Xiaopeng
    2024, 53(4):  14. 
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    To simulate the in situ influence of pressure,temperature and other factors on the mechanical performance of cemented backfill in a laboratory environment,this paper designed a testing apparatus considering the cooperative control of applied pressure and temperature during the curing of cemented backfill samples. The influence of applied pressure and environmental temperature during curing on the early-age strength of cemented backfill samples was studied. The results show that both curing pressure and curing temperature have a noticeable influence on the early strength of cemented backfill samples. The curing pressure is beneficial to the early strength development of cemented backfill samples. With the increase in curing temperature, the strength of the cemented backfill samples initially raised as well,then decreased while the curing temperature reached 55 ℃. Under the coupled influence of curing pressure and curing temperature,high temperature is beneficial to the early strength development of cemented backfill samples.
    Experimental Study on Brazilian Splitting Fracture Characteristics of Prefabricated Fissured Sandstone
    ZHANG Mingyuan, YAO Huayan, JIANG Hao, LIU Wu, WANG Xuyang, ZHU Yiyuan
    2024, 53(4):  20. 
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    In order to study the influence of fissures on the macroscopic fracture morphology of rocks,the Brazilian splitting tests of sandstone under three fissure types,single fissure,collinear double fissures and parallel double fissures,were carried out. The fracture morphology of sandstone samples under the three fissure types with different inclination angles was analyzed and classified,and the changes of tensile strength of the three fissure types under different fissure inclination angles were analyzed. Test results showed that the existence of fissures weakened the tensile strength of the rock,and the number of fissures, the inclination angle of the fissures and the geometric arrangement between the fissures affected the fracture morphology and tensile strength of the specimen. There were five types of fracture forms in single-fissure sandstone samples,four fracture forms in collinear double fissures,and three types of fracture forms in parallel double fissures,and the heterogeneity of the rock led to different fracture morphologies of samples under the same fissure inclination. The tensile strength of single fissure and collinear double fissures sandstone is the largest at 0° fissure inclination,with the increase of fissure inclination,the tensile strength of single fissure sandstone first decreases and then rises and then decreases,the tensile strength of collinear double fissures sandstone shows a downward trend,while the tensile strength of parallel double fissures sandstone is the greatest at 45° fissure inclination.
    Impact Pressure Characteristics of Radial Uncoupled Charge on Hole Wall
    LOU Xiaoming, WU Shuo, YAO Bingjin, XIE Yelong, HU Yan, CHEN Bigang
    2024, 53(4):  28. 
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    The radial uncoupled charge structure is widely used in practical blasting engineering. In order to explore the variation law of the impact pressure of the hole wall of the radial uncoupled charge,based on the shock wave theory,the shock tube model is used to simplify the action process of the wave system in the hole under the condition of the radial uncoupled charge. The impact pressure of the blast wave in the hole on each medium surface is studied. The calculation expression of the initial impact pressure of the hole wall under the condition of radial uncoupled charge is obtained,and the action process of the blast wave under the condition of radial uncoupled charge is simulated. The results show that the existence of the radial air layer greatly reduces the pressure of the explosion shock wave. The peak pressure of the hole wall decays exponentially when the uncoupling coefficient is 1~2,and the decay rate is slow when the uncoupling coefficient is greater than 2. There are multiple peaks when the shock wave acts on the hole wall,and the initial peak pressure is the largest,and the subsequent peak pressure gradually decreases with time. With the increase of the uncoupling coefficient,the initial peak pressure gradually decreases and the time to reach the peak pressure gradually delays. The larger the uncoupling coefficient is,the more obvious the multi-peak characteristics are. When the uncoupling coefficient is small,the peak pressure is larger,which will cause greater damage to the surrounding rock. In order to reduce the damage to the surrounding rock and meet the corresponding blasting requirements,the multi-peak characteristics when the decoupling coefficient is large should be fully utilized,and a reasonable radial charge coefficient should be selected according to the rock properties.
    Experimental Study on Shear Mechanical Properties of PPGF-Limestone Bonding Surface
    YANG Chao, JIANG Shuyin
    2024, 53(4):  37. 
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    In order to explore the shear cracking failure law and mechanical response mechanism of the slurry crack bonding surface,a new graphene based grouting material PPGF was taken as the research object. Direct shear tests of PPGFlimestone bonding body were carried out under different graphene content,crack roughness,and normal load conditions. The influence of graphene,crack roughness,and normal load on the cracking,shear stress,and normal displacement of the bonding surface were obtained. The results show that with the increase of graphene content,the maximum shear stress shows a pattern of first increasing and then decreasing,and the increase is maximum when the content is 0. 036%. When the shear failure of the bonding surface is dominated by climbing slip,the influence of graphene and normal load on the shear expansion displacement is relatively small. When the shear failure is dominated by shear slip,the influence of graphene and normal load on the shear expansion displacement is relatively large. Graphene can increase the bonding strength of PPGF and delay the cracking of the bonding surface. The cracking shear displacement increases with the increase of roughness and decreases with the increase of normal load.
    Experimental Study on Mechanical Properties and Support of High Strength Prestressed Bolt
    YUE Xizhan, YANG Ziyi, LI Yingfu, SUN Maoru
    2024, 53(4):  46. 
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    High-strength prestressed bolt support is a further optimization development of traditional bolt support technology. Due to the complex geological characteristics of deep roadway,such as surrounding rock breakage and high stress,more high-strength prestressed bolts are used instead of traditional bolts. In this paper,the mechanical properties of high-strength prestressed anchor bolts are compared and analyzed through theoretical analysis,prestress conversion test,pull out test of left and right rotary anchor bolt and anchorage force test,and the supporting mechanism of new left-handed high-strength prestressed anchor bolts is revealed. The results show that:① Theoretical analysis of the action mechanism of the anchor rod in the surrounding rock,elucidating the reinforcement of the prestressed anchor rod on the surrounding rock. ② The efficiency of converting the torque of rolling wire bolt into preloading force is about 1. 7~1. 9 times that of equal strength full thread bolt. The mechanical properties of left-handed rolling wire bolts with different diameters are better than those of right-handed full thread bolts. The anchoring force of left-hand threaded steel bolt is greater than that of right-hand threaded steel bolt. ③ Analyze the structure of the new left-handed high-strength prestressed bolt,which has the advantages of high prestress,high anchoring force and large effective section. It provides a useful reference for the optimization and innovation of deep roadway surrounding rock support technology.
    Response Behavior of Artificial Fracture Propagation to Natural Fractures in Oriented Hydraulic Fracturing of Hard Rock Mass
    WANG Weicheng, HUANG Minqing, HUANG Min, TANG Shaohui
    2024, 53(4):  53. 
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    Hydraulic fracturing is a key preconditioning approach in block caving mining of hard-rock metal mines,however, natural fractures within the orebody tend to limit the oriented fracture propagation and spatial morphology of artificial fractures. To understand the influence of the natural fracture′s length and horizontal distance on the propagation path of oriented fracture within copper orebodies with natural fractures,a finite element numerical model embedded with pore pressure cohesive elements was established using ABAQUS,and hydraulic fracturing behaviors was simulated under variable natural fracture lengths and horizontal distance conditions. Results show that the length and horizontal distance of natural fractures lead to a positive effect on the propagation morphology and propagation law of fractures. The natural fracture length has an exponent relation to the propagation radius of artificial fractures,while the horizontal distance of natural fractures shows a linear relation with the propagation radius of hydraulic fractures. Regarding 0~1. 5 MPa low in-situ stress difference,with the decrease of natural fracture horizontal distance,or with the increase of natural fracture length,the propagation radius of hydraulic fracture is larger, and other response laws of hydraulic to natural fracture. The study results have a possitive guilding significance for the directional propagation and control of hydraulic fractures under the condition of hard rock natural fractures.
    Research on the Characteristics of Oil Shale Mechanics and Destruction Fracture under the Influence of Oil Content
    GAN Ze, YANG Xi, LI Fuping, GAN Deqing
    2024, 53(4):  62. 
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    There is a huge difference in oil content of oil shale,and this change in oil content will cause differences between their mechanical properties and destructive breakdown characteristics. Select vertical oil shard samples with a oil content of 6. 5%,6%,5%,and 3%. It carried out a single-axis compression experiment,field strain and acoustic emission monitoring. Studies have found that the increase in oil content will reduce the pressure resistance of oil shale and transform it from crispy to delay. High oil-content oil shale is prone to shear-tensor damage. Low oil-content oil shale destruction mode is biased towards tensor damage. During the loading process,the main strain field of the oil shale is transformed from a uniform distribution to a concentrated distribution. The shear phenomenon in the field change weakened. A high oil-content sample ringing count is the growth of the stepped type. After the damage,there is still a high ringing count. The high ringing count of low oil-content oil shale occurs only when it is destroyed. Under the same elasticity conditions,the deformation of low oil-content oil shale in the energy storage stage is smaller. The high oil-content sample has a certain delay. After the sample reaches the peak of the stress, the elasticity is not fully released,and some elasticity is still retained. Low oil-content samples have strong anti-deformation capacity, so under the same strain conditions,their scattered energy is higher.
    Mechanical Properties and Failure Characteristics of Rock Masses with Different Degrees of Fragmentation under Triaxial Compression
    ZHANG Jie, GU Xiuhua, XIONG Zanmin, WEN Zhenjiang, WANG Xiaotian
    2024, 53(4):  70. 
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    Under deep mining conditions,geological conditions deteriorate,and fractured rock masses are prone to large deformation and failure. The discrete fracture network (DFN) in 3DEC software is applied to establish a synthetic rock mass (SRM) model considering different degrees of fragmentation in deep underground areas. The mechanical properties of highstress fractured rock masses under confining pressure loading conditions are studied,and the relationship between rock integrity coefficient,compressive strength,and elastic modulus is established. The experimental results show that rock masses with a high degree of fragmentation exhibit strong ductile failure characteristics under uniaxial compression tests;As the confining pressure increases,the compressive strength and plastic deformation of the stress-strain curve at the yield stage significantly increase with the same degree of fragmentation,and the amplitude of post-peak stress drop slows down;The micro cracks inside the rock mass first originate at the end of the joint surface and its intersection,and the larger the number of joints,the faster the crack development and connection;When subjected to high confining pressure loading,the failure mode of the specimen changes from tensile failure to shear slip failure. The failure characteristics of fractured rock masses are closely related to their degree of fragmentation and the stress-loading environment,which is an important reference for engineering construction and design.
    Damage Creep Model of Roadway Concrete Based on Energy Conservation Principle
    REN Yuejing, YAN Ruizhen
    2024, 53(4):  76. 
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    In order to better obtain the long-term deformation characteristics of deep underground concrete structures,the uniaxial mechanical properties and creep properties of concrete are tested by TAW-2000 test system. The creep deformation law of concrete under different stress and the long-term strength of concrete are analyzed. Without considering the internal heat exchange of rock,the accelerated creep of rock is studied by the law of conservation of energy,and the damage creep model of concrete based on the principle of conservation of energy in one-dimensional state is established. On this basis,it is assumed that the mechanical parameters and rheological parameters of concrete structures in deep underground engineering are functions of time. An unsteady creep model based on the principle of energy conservation is constructed. The results show that the damage creep model of concrete based on the principle of energy conservation can better describe the whole creep process curve of concrete. The correlation coefficient between the model curve and the test curve is above 0. 95. This shows the correctness of the creep damage model established in this paper. The model not only accurately reflects the creep characteristics of the attenuation and stable creep stages. The shortcomings of accelerated creep are also well described.
    Study on the Mechanical Characteristics of Coal Rock and the Law of Infrared Radiation of Loading Rate
    PENG Yanyan, HAN Panrong, WANG Yanli, WANG Chonghuan, FAN Xiao
    2024, 53(4):  82. 
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    In order to study the mechanical properties of coal rock at different loading rates and the infrared precursor information of its instability failure,under different loading rates,the TP coupling testing machine and high-precision infrared thermal imager,and five loading rates of 0. 01,0. 02,0. 03,0. 04 and 0. 05 mm/ s were used to perform uniaxial compression tests,and the test results showed that the proportion of elastic deformation stage of coal rock line was significantly reduced by the increase of loading rate. The temperature difference between the peak and minimum value of the average temperature curve of coal rock decreases with the increase of loading rate. The increase of loading rate hinders the early time point of the cooling precursor phenomenon of coal rock instability failure.
    Construction of Concrete Creep Model Considering the Dual Effects of Temperature and Time
    XIANG Xuemin, WEN Zhu, GUO Limei, XU Hui, WANG Nan
    2024, 53(4):  87. 
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    In order to study the influence of temperature on the creep characteristics of concrete structures,the triaxial creep tests of concrete under different temperatures were carried out,and the axial creep characteristics of concrete structures under different temperatures were analyzed. Under the action of temperature,the internal damage of concrete is related to the non-uniformity parameter,and the relationship between the non-uniformity parameter and temperature is established. It is assumed that the concrete creep model is a function of temperature and time. Combined with the above damage variables and the probability model of micro-element strength distribution,a concrete creep model considering the dual effects of temperature and time is established. Based on the least square method and experimental data,the accuracy of the model is verified,and the superiority of the Nishihara model is further verified. The results show that the creep damage model curves under different temperatures are in good agreement with the experimental data,and the correlation coefficient is above 0. 95,which shows the correctness of the established model. At the same time,the agreement between the model and the experimental data is better than that of the Nishihara model,and it has certain advantages in describing accelerated creep. The theoretical model provides a theoretical basis for the long-term deformation prediction of concrete supporting structure in underground engineering.
    Dynamic Damage and Energy Evolution Mechanism of Magnetite under Water Immersion
    LU Yanze, GAN Deqing, WANG Sheguang, LIU Zhiyi, WANG Qinggang, WANG Lijie
    2024, 53(4):  95. 
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    In order to analyze the dynamic damage characteristics and energy transport law of magnetite under water immersion effect,the magnetite was immersed in water for different times,and the dynamic compression tests with different impact load values were carried out by using the Hopkinson pressure bar test system (SHPB). The results show that the dynamic failure deformation process of magnetite under water immersion is divided into three stages:elastic deformation,yield damage deformation and instability failure. The dynamic compressive strength of magnetite decreases with the increase of immersion time, and the relationship between them is exponentially decreasing. The decreasing value of the dynamic compressive strength of magnetite first increases and then decreases,and the decreasing value of the dynamic compressive strength is the largest when the immersion time is 14 d. With the increase of immersion time,the fragmentation degree of magnetite increases,but the overall fragmentation uniformity is the best when the immersion time is 14 d. The energy evolution process of immersed magnetite is divided into three stages:elastic storage stage,energy conversion stage and energy dissipation stage. Increasing the dynamic load value can improve the energy utilization rate of magnetite with immersion time of 14 d,and the energy consumption density of magnetite is the largest under this water immersion time,which indicates that the magnetite with water immersion treatment can effectively improve the uneven degree of ore fragmentation,reduce the workload of secondary fragmentation,and decrease the blasting energy consumption to a certain extent. The research results provide certain theoretical guidance for the safe and efficient mining of water-rich orebodies.
    Effect of Polyacrylamide Inhibitors on the Regulation of Floatability Difference between Diaspore and Kaolinite
    SHAO Xiufeng, ZHANG Suhong, MA Yue
    2024, 53(4):  102. 
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    In view of the poor adsorption selectivity of collectors on the surface of diaspore and kaolinite,three different types of polyacrylamide inhibitors were added to adjust the selective adsorption difference of collectors on the surface of minerals. The effect of inhibitor type on the adsorption capacity difference and interaction change of the collector propylene bisdodecylamide propyl dimethyl ammonium chloride (DAPDPAC) on the mineral surface,and the effect of the inhibitor on the flotation of the two minerals were studied. The flotation test results showed that compared with nonionic polyacrylamide (NPAM) and anionic polyacrylamide (APAM),cationic polyacrylamide (CPAM) showed a significant difference in flotation adjustment of the two minerals by the collector. When the concentration of CPAM was 80 mg/ L,the recovery rate of diaspore was significantly inhibited,while the recovery rate of kaolinite was almost unchanged. In the acidic to weakly alkaline environment,diaspore and kaolinite could be well separated by flotation. The results of infrared spectroscopy showed that the addition of inhibitor CPAM effectively hindered the adsorption of DAPDPAC on the surface of diaspore,while the adsorption on the surface of kaolinite did not change significantly. The results of adsorption capacity,Zeta potential and XPS tests showed that when the dosage of CPAM was more than 80 mg/ L,the difference of adsorption capacity of DAPDPAC on the surface of diaspore and kaolinite remained above 9. 76×10-7 mol/ g. Therefore,CPAM can effectively regulate the selective adsorption of DAPDPAC on the surface of diaspore and kaolinite,which is beneficial to strengthen the flotation separation of diaspore and kaolinite by DAPDPAC.
    Effect of Ceramic Medium Stirred Mill on Dissociation Characteristics and Separating Potential of Coking Coal Middlings
    GUO Keqi, KOU Zongyang, GUO Wang, LI Yonggai, XING Yaowen, GUI Xiahui
    2024, 53(4):  111. 
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    In order to study the selective dissociation characteristics of coking coal middlings in stirred mill,taking the coking coal middlings of Guobei Coal Preparation Plant as the object,the sample properties,grinding conditions optimization, dissociation characteristics of grinding products and particle shape characteristics were studied. The flotation effects of grinding products of stirred mill and rod mill under the same grinding fineness were compared. The results showed that under the optimal grinding conditions of stirred mill grinding time of 4 min,ceramic ball diameter of 6 mm,medium filling rate of 60% and grinding concentration of 55%,the grinding products with -0. 074 mm content of 79. 39% were floated,the concentrated coal (Ad = 11. 50%) products with yield of 61. 49% were obtained. At the same grinding fineness,the grinding time required by the stirred mill was shorter,and the yield of high-ash fine mud was lower. The yield of flotation concentrated coal (Ad =11. 50%) of the grinding products was 9. 82 percentage points higher than that of the rod mill,indicating that the stirred mill had a better dissociation effect. SEM analysis further confirmed that there were less micro-fine gangue minerals on the surface of the stirred mill grinding products,the particle sphericity (R0 ) was low,and the elongation (EW) was high,which was conducive to the adhesion of particles and bubbles. The research results can provide process ideas for selective dissociation of coking coal middlings.
    Study on the Crystallization Behavior and Floatability of Calcium Fluoride Particles in Fluorine-containing Wastewater
    ZHANG Yuxi, CI Qu, LI Junxiao, KONG Linghao, QIAN Yupeng, HUANG Siyun, LIU Dongbin
    2024, 53(4):  121. 
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    In order to solve the problem of environmental pollution in the process of processing and utilization of fluorine resources,improve the comprehensive utilization rate of fluorine resources in fluorine-containing wastewater,the sedimentation behavior and particle size characteristics of calcium fluoride crystallization particles in fluorine-containing acidic wastewater were systematically studied,and the flotation characteristics of calcium fluoride crystallization particles were explored. Combined with the chemical precipitation formation process of calcium fluoride simulated by Visual MINTEQ software,the phase composition of crystallization particles was characterized by XRD,and the action mechanism between NaOL and calcium fluoride particles was analyzed by Zeta potential test. The results showed that when calcium chloride was used to treat fluorine-containing acidic wastewater,calcium fluoride crystallization particles could not be formed under strong acid conditions. When pH> 5,stable calcium fluoride crystallization precipitation products could be obtained. And the higher the concentration of F- in the wastewater,the more the number of crystallization particles,the larger the particle size. The obtained calcium fluoride crystallization had high purity and almost no other impurities. When the pH was 5~9,sodium oleate could be adsorbed on the surface of calcium fluoride crystallization particles,so that it had good floatability,and the dosage of sodium oleate was proportional to the concentration of F- in the wastewater,and the flotation recovery effect was good. The results of this study can provide a theoretical reference for the treatment of fluorine-containing wastewater and the recovery of calcium fluoride resources.
    Study on Collision and Adhesion Mechanism between Bubbles and Chalcopyrite Surface with Different Roughness in Xanthate Solution System
    ZHANG Cheng, CHENG Yuting, PENG Yaoli, XIE Guangyuan, XIA Wencheng
    2024, 53(4):  127. 
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    In the process of chalcopyrite flotation,the change of mineral surface roughness and xanthate concentration will directly affect the adhesion and spreading of bubbles and mineral surface,thus affecting the flotation effect. In order to investigate the influence of the roughness of chalcopyrite surface and the concentration of xanthate on the collision and adhesion behavior of bubbles and chalcopyrite,the samples with different roughness were obtained by grinding chalcopyrite with sandpaper, and then the collision and adhesion test of bubbles on the mineral surface was carried out. The local velocity of bubbles, the collision and adhesion time of bubbles,the change of three-phase contact line length with time and the contact angle of bubbles were tested and analyzed. The results showed that the surface of chalcopyrite with larger roughness had a larger size and a larger number of rough structures,which promoted the thinning and rupture of the hydration film between the bubbles and the mineral surface,which was conducive to the formation of adhesion. However,after adhesion occurred,the rough structures of chalcopyrite surface hindered the further spreading of bubbles on the chalcopyrite surface. The increase of xanthate concentration increased the thickness of the hydrophobic film formed on the surface of chalcopyrite,enhanced the covering effect of the rough structure and the electronegativity on the surface of the chalcopyrite,improved the hydrophobicity of chalcopyrite. It was not conducive to the formation of adhesion between bubbles and chalcopyrite,but was conducive to the further spreading of bubbles after adhesion on the surface of chalcopyrite. The results can be used for the study of efficient flotation recovery and utilization of chalcopyrite.
    Experimental Study on Comprehensive Recovery of a Low-grade Complex Refractory Iron and Tin Ore in Myanmar
    TIAN Xiaosong, WU Liwei, ZHAO Xun, LIANG Zeyue, DAI Huixin, LÜ Yuchen, WANG Feiwang
    2024, 53(4):  135. 
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    A low-grade iron tin ore in Myanmar contains iron of 29. 79% and tin of 0. 495%,and the gangue composition is mainly SiO2. The main valuable minerals are magnetite and cassite,which are closely symbiosis,and the grain size is fine. In order to determine the efficient development and utilization process of the ore,based on the study of raw ore properties,the process flow of wet low-intensity magnetic separation (LIMS) for iron selection,cassiterite recovery (shaking table gravity separation (STGS),high gradient magnetic separation (HGMS) after middle ore regrinding for iron removal and STGS),flotation desulphurization,magnetic separation for iron removal with tin comprehensive roughing concentrate(LIMS+HGMS) process was obtained for beneficiation experimental research. The results showed that the whole process closed-circuit test finally obtained tin concentrate with a tin grade of 57. 956% and recovery rate of 69. 08%,iron concentrate with an iron grade of 65. 21% and recovery rate of 48. 22%,sulfur concentrate with sulfur grade of 46. 35% and recovery rate of 38. 31%. The impurities contained in three kinds of concentrate products,such as iron,tin and sulfur,are not exceeded,and the tin grade of the total tailings is reduced to 0. 153%,which realizes the comprehensive recovery and utilization of iron tin ore resources.
    Study on Phase Transformation and Flotation Behavior of Reduction Roasting of Bastnaesite
    ZHAO Yingjie, TANG Jiayan, HE Jianing, ZHAO Fang, WANG Xiaoping, WANG Jieliang, CAO Zhao
    2024, 53(4):  142. 
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    The reduction roasting method is often used in the process of iron separation in Bayan Obo mine. During the roasting process,the phase transformation of rare earth minerals will occur and affect its flotation behavior. In this paper,the physical phase changes of cerium fluorocarbon (Cerium fluoride) after roasting at 400,450,500,550 ℃ and the effects of the flotation behaviour of Cerium fluorocarbon (Cerium fluoride) and roasted Cerium fluorocarbon (Cerium fluoride) at 500 ℃ under the action of two trappers,octyl hydroxamic acid (OHA) and diethylhexyl phosphate (2ZHP),were investigated by means of XRD analytical tests,SEM-EDS tests,flotation tests,contact angle tests,kinetic potential tests of mineral surfaces,and X-ray photoelectron spectroscopy (XPS) analyses. XRD and SEM-EDS test results show that REFCO3 is obtained when calcined at 450 ℃,RE3O4F3 is partially decomposed when calcined at 500 ℃,and RE3O4F3 is completely transformed when calcined at 550 ℃. The collector OHA has poor flotation effect on the new substance RE3O4F3 produced by the calcination of cerium fluocerite at 500 ℃,The contact Angle test showed that 2ZHP could strengthen the surface hydrophobicity of bastnaesite and roasting bastnaesite at 500 ℃. Zeta potential test showed that compared with OHA,2ZHP could adsorb bastnaesite more effectively. XPS test showed that OHA and 2ZHP played a trapping role through mineral surface adsorption. However,the adsorption capacity of 2ZHP on the surface of calcined bastnaesite is greater. while the collector 2ZHP has the same collecting capacity for REFCO3 and RE3O4F3 produced by the calcination of cerium fluocerite at 500 ℃. 2ZHP is more suitable for the flotation of cerium fluoride after roasting.
    Research Progress on the Preparation and Mechanism of Magnesium Hydroxide
    WANG Meijia, BAI Limei, MA Yuxin, ZHAO Liucheng, LI Shaoying, CHENG Zimeng
    2024, 53(4):  150. 
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    Magnesium hydroxide is an important magnesium-based mineral material and one of the ways to realize the high-value utilization of magnesium resources. However,the morphology change of magnesium hydroxide is affected by the raw materials,methods and conditions of preparation,which directly affects the application of magnesium hydroxide. Therefore,the preparation process,advantages and disadvantages of physical crushing method,direct precipitation method and magnesium oxide hydration method are analyzed in detail. It is pointed out that magnesium hydroxide has the characteristics of high thermal stability and large specific surface area,and the relationship between the morphology of magnesium hydroxide and its application in different ways such as flame retardant of polymer materials,adsorption treatment of heavy metal wastewater and degradation of dye wastewater,so as to provide reference for more potential applications of magnesium hydroxide. It is proposed that in the process of crystal growth of magnesium hydroxide,the growth habit of crystal plane can be changed by adding crystal plane regulating agent and doping cation,and the change of supersaturation of solution can also promote or inhibit the nucleation and growth of crystal,thus affecting the morphological change of magnesium hydroxide. It is pointed out that the industrial production of magnesium hydroxide with high purity and specific morphology is still facing challenges. The formation mechanism of magnesium hydroxide crystal defects under different conditions is not clear. It is still necessary to further study the types of dislocations and interstitial defects that may exist in the crystal to improve the performance of magnesium hydroxide and expand the field of high-value utilization of magnesium resources.
    Flotation Behavior of Rhodochrosite and Gangue Carbonate Minerals in a New Green Flotation System
    ZHU Zizheng, TANG Yun, DENG Zhengbin, WU Bo
    2024, 53(4):  160. 
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    Taking rhodochrosite and gangue carbonate minerals dolomite,calcite and siderite as the research objects,the effects of the pH value of the slurry and the amount of chemicals in the new green flotation system on the four flotation behavior and interfacial interaction mechanism of carbonate minerals. The results show that the collector ZJS and the inhibitor JBS have a strong synergistic effect and are the best combination of agents for the reverse flotation separation of rhodochrosite and gangue carbonate minerals. The dosage of collector ZJS is 60 mg/ L,and the inhibitor JBS is 60 mg/ L. When the dosage of JBS agent is 20 mg/ L,the recovery of rhodochrosite is only 10%,the recovery of dolomite is more than 40%,and the recovery of calcite and siderite is more than 55%. Zeta potential,FTIR and XPS analysis results show that in the ZJS collection system,the inhibitor JBS acts on the interfaces of four carbonate minerals in a physical adsorption manner,and the adsorption capacity of JBS at the rhodochrosite interface is stronger than that of other gangue carbonates. The mineral makes rhodochrosite more hydrophilic and can be separated by reverse flotation. This new flotation system is expected to remove part of the calcium,magnesium and iron ions from high-grade manganese carbonate ore or magnetically separated manganese carbonate concentrate,providing a basis for further upgrading and reducing impurities in manganese carbonate ore.
    Numerical Simulation Study of Surface Movement Patterns of Large Mining Height Coal Seam Mining in Loess Hilly Terrain
    CHEN Hongkai, GUO Qingbiao, GUO Guangli, MA Honghao, LUO Jin
    2024, 53(4):  170. 
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    The surface movement characteristics of coal seam mining in loess hilly terrain are significantly different compared to plain areas. In order to analyze and reveal the anomalous mechanism of coal mining surface subsidence in hilly topography. The surface subsidence caused by top coal caving mining in loess hilly terrain was measured,and the surface movement characteristics and related parameters were analyzed and studied. A 3D model of the considered terrain was established by using the Rhino software and imported into the 3DEC software for numerical simulations. The movement of rock formations during mining and the evolution of plastic damage within the hilly are analysed. The results show that the surface movement of 1313 working face is intense. The starting distance of surface subsidence is less than 30 m. The leading infection distance is 73 m. The leading infection angle is 68. 7°. The strike boundary angle and the upper boundary angle are 40. 3°,and the strike movement angle and upper movement angle are 37. 8°. The dangerous movement range with the horizontal tensile deformation of 2 mm/ m as the movement boundary is significantly larger than the surface movement basin range determined by the subsidence value of 10 mm. Numerical simulation is used to analyze the mining slip process in loess hilly terrain. The results indicted that when the working face is retrieved 30 m along the strike from the open-off cut,the stress equilibrium of the rock around the mining area is broken,and the top plate is shear damaged by the self-weight and the load of the overlying rock layer,and the rock around the mining area is plastic yielded. When the working face is retrieved 120 m,the coal seam is in the non-full mining stage,the shear damage zone of the rock at the bottom of the beam mount is penetrated,and the slope is sheared to the neighboring empty side under the action of gravity. Compared with the section with the surface slope of 15°,the maximum horizontal movement in the negative direction of the X-axis of the section with the surface slope of 18° and 22° increases by 107. 3% and 246. 5%.
    Study on Automatic Identification Method of Wide-area InSAR Mining Subsidence Area Based on U2-Net
    LIN Tao, FAN Hongdong, SUN Ye, LI Xiangwei, ZHUANG Huifu
    2024, 53(4):  177. 
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    China′s underground coal mines are large and wide,and underground mining is highly concealed. The existing methods of manual investigation,remote sensing detection and field measurement are difficult to meet the requirements of automatic identification of large-scale mining subsidence areas,which is not conducive to the efficient supervision and dynamic monitoring. Therefore,this paper proposes an automatic identification method of mining subsidence area based on U2-Net wide-area synthetic aperture radar interferometry (InSAR). This method trains convolutional neural network (CNN)through simulation data sets of various deformation gradients and noise levels,so that it can output a binary matrix containing mining subsidence location information in one step from the differential interferogram. The test results show that the mean pixel accuracy (MPA) and mean intersection over union (MIoU) of U2-Net reach 0. 916 3 and 0. 911 9,respectively,which are higher than the other two models in the experiment. It can better suppress noise and highlight deformation signals. On the InSAR interferograms covering the Shendong mining area at different time intervals,U2-Net automatically identified interferograms covering an area of more than 54 600 km2,and detected multiple subsidence areas with clear and smooth boundary information. The average accuracy of recognition reached 92. 45%. The results show that compared with other networks,U2-Net can fuse multi-scale and multi-level features with less computation through a two-stage nested U-shaped structure,which has significant advantages in noise suppression and deformation region recognition. It can be indicated that joint deep learning can serve the detailed investi-gation of refined mining subsidence areas,promote the application of InSAR technique,and provide a new technical method for intelligent identification of wide-area mining subsidence areas.
    Study on the Development Characteristics and Height Prediction of Water Conducting Fracture Zones in the Deep Mining Area of Shanxi-Mongolia
    CHEN Yankang, GUO Guangli, MENG Hao, ZHANG Liangui, ZHENG Hui, LI Huaizhan, ZHANG Haoyu
    2024, 53(4):  186. 
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    The development height of water conducting fracture zones (WCFZ) is an important basis for mine water prevention and safety mining. Due to the special sedimentary environment and process in the Shaanxi-Mongolia mining area,the height of WCFZ differs greatly from traditional understanding in this region. Considering the current lack of calculation methods for the height of WCFZ in the Shaanxi-Mongolia mining area,a simulation using UDEC was conducted on the development laws and evolutionary characteristics of WCFZ under different mining progress at the 2217 working face of the Yingpanhao coal mine in Ordos city. The relationship between large energy events and the development of WCFZ was analyzed,and a precise prediction method for regional WCFZ height was established based on the GA-SVR algorithm. The results showed that the characteristics of the thick sandstone layer of Zhuiluo formation give it the characteristics of a hard rock layer during overlying rock movement, and the fracture zone underneath it develops fully and stabilizes into a "saddle shape". Microseismic monitoring data can accurately reflect the height of WCFZ in the region,with a relative error of only 3. 90% in prediction. The coefficient of determination R2 of the established WCFZ height prediction model is 0. 81,the relative average error r is 14. 55%,and the prediction accuracy is significantly better than that of empirical formulas (R2 <0,r = 59. 57%). The research results have important practical significance for water conservation mining,safety production design,and mine water control in the Shaanxi-Mongolia mining area.
    Motion Analysis and Gait Planning of Hexapod Robot in Underground Stope of Metal Mine
    ZHANG Xufei, WANG Yunsen, MENG Xiangkai, WANG Yu, ZHOU Hong, LI Yuanhui
    2024, 53(4):  193. 
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    The special structural design of hexapod robots has sparked interest in biomimetic robotics research,particularly due to their remarkable obstacle-crossing capabilities. However,the ore accumulation and rugged characteristics of the metal mine underground stope poses significant challenges to the walking stability and obstacle avoidance of this kind of robot. Therefore,in order to make the hexapod robot have better passability in the mine,its motion ability and gait planning are studied. Firstly,the structure of hexapod robot is designed according to the nature hexapod,and the kinematics of its legs is analyzed. Then,the straight gait for stope is planned,and a line-cycloid composite trajectory is designed to improve the obstacle crossing ability according to the stope road environment. At the same time,the stability of robot climbing is analyzed,and the climbing gait is optimized. Finally,the simulation and field simulation tests of the planning gait were carried out. The simulation and test results show that the planned foot trajectory can cross the obstacles with 85% of the leg height,and has better obstacle avoidance ability for the stope road formed by ore accumulation. Triangular gait is easy to slip in the transition stage between the bottom and the top of the slope,while lateral gait can achieve a smooth transition and better climbing performance.
    Truck Scheduling Optimization Algorithm for Surface Mine Based on Lightweight Graph Attention Mechanism
    HUANG Shi, CHEN Zhaoyu, ZENG Lei
    2024, 53(4):  202. 
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    Effectively managing and scheduling open-pit mine trucks can significantly improve transportation efficiency and reduce mining operation costs. Existing research focuses on using Deep Reinforcement Learning (DRL) to construct learning models for solving path optimization problems. However,when training models with Transformer architecture parameters,a large number of redundant parameters are generated. To address this issue,this paper proposes a lightweight graph attention mechanism for optimizing open-pit mine truck scheduling. Specifically,the Adams method,a numerical solution for differential equations,is employed in the weight learning of the Transformer model. A residual training method based on Adams is proposed to improve the optimization accuracy of the network in the later stages and further compress the model size,efficiently solving the open-pit mine truck scheduling optimization problem. The research shows that this method can reduce the optimal gap while compressing the parameter size of the source model to half,reducing the training dependency on GPU devices. Performance verification of the algorithm is conducted using randomly generated open-pit mine truck datasets,demonstrating that the Adams- Transformer model helps improve the efficiency of open-pit mine truck scheduling.
    Path Planning Optimization of Mine Roadway Inspection Robot Based on SLAM Technique
    LIN Yanxia, SU Dan
    2024, 53(4):  209. 
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    Aiming at the characteristics of complex roadway environment and narrow road in mining area,a path planning optimization method of roadway inspection robot based on SLAM (Simultaneous Localization and Mapping) technique is proposed to realize the autonomous positioning and map construction of the robot. Firstly,a variety of sensors such as LiDAR and RGB-D cameras are fused to obtain 3D point cloud data of mining area,and SLAM algorithm is used to construct 3D map of mining area in real time. At the same time,through the registration of the currently obtained point cloud data and the built map,the robot can realize the autonomous positioning in the mining area. Secondly,an incremental A∗ optimization algorithm is proposed for path planning in view of the narrow,bending,branching and other complex environments in mines. Based on the traditional A∗ algorithm,the algorithm introduces optimization strategies such as path smoothing and corridor width constraints, which can generate smooth feasible paths that meet the constraints of complex mining environment. The algorithm is updated incrementally, and only needs to research the changed local area,which greatly reduces the calculation time of the overall path planning. The experimental results show that compared with the traditional route planning method,the algorithm can complete the inspection task more quickly and accurately,which provides a reference for the popularization and application of mine roadway inspection robot.
    Mining Remote Sensing Image Enhancement Algorithm Based on Deep Residual Learning in Discrete Wavelet Domain
    LI Yike, WANG Chunmei
    2024, 53(4):  215. 
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    Enhancing remote sensing images of mining areas can significantly improve subsequent image interpretation and monitoring analysis efficiency. Traditional methods for enhancing remote sensing images in mining areas often involve filtering, grayscale transformations,etc. ,which can lead to significant loss of detail in the image,greatly affecting image interpretation. In recent years,deep learning methods have gradually been applied to image enhancement processing. However,this method heavily relies on model design and parameter tuning,requiring a large number of experiments and optimizations to achieve desirable results. Combining deep learning (DL) with discrete wavelet transform (DWT),a mining area remote sensing image enhancement algorithm based on deep residual learning in the discrete wavelet domain is proposed. Firstly,the image is subjected to single-level 2D discrete wavelet transform to obtain 4 subbands. Then,the coefficients of the 4 subbands are input into a deep residual network to predict corresponding residual images. These residual images are added to the original 4 subband images to create new subbands for the 2D wavelet transform. Finally,the enhanced image is obtained through 2D inverse discrete wavelet transform. The test results show that:compared with methods such as histogram equalization wavelet transform and super- resolution reconstruction convolutional neural network,the proposed algorithm has a good advantage in terms of image visual effect,peak signal-to-noise ratio,structural similarity,mean square error and other evaluation indicators,reflecting that the combination of discrete wavelet transform and deep learning is helpful to improve the visual effect of remote sensing images in mining areas and facilitate subsequent image interpretation and interpretation.
    Numerical Analysis of the Influence of Underground Mining on the Stability of Existing Slopes under Freeze-thaw Cycle
    GAO Zhenyu, MIAO Haodong, CHANG Yuan
    2024, 53(4):  221. 
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    To study the stability of existing freeze-thaw slopes under different underground mining conditions,this paper conducted numerical simulations using 3DEC to analyze the mining stability of the slopes considering different freeze-thaw cycles. The analysis focused on the effects of different underground mining speeds and freeze-thaw cycles on the slopes regarding displacement,stress,plastic zone,safety factor,and energy. The results indicate that increased freeze-thaw cycles increase slope displacement and stress. The vertical stress distribution in the roof of the goaf exhibits a symmetrical pattern with the coal pillar at the center. When the mining speed changes from 30 meters/ step to 50 m/ step (mining a distance of 200 m),the maximum vertical stress of the roof increases from 10 MPa to 30 MPa. The extent of tensile failure on the surface of the freeze-thaw slope gradually increases with an increase in the number of freeze-thaw cycles. The safety factor of the slope decreases as the number of freeze-thaw cycles increases,and there is a risk of instability after 20 freeze-thaw cycles. The freeze-thaw slope′s gravitational potential energy and dissipation energy are minimally affected by the number of freeze-thaw cycles and show limited sensitivity to changes in mining rate,even under the same freeze-thaw cycle conditions. However,the kinetic energy released by the freeze-thaw slope increases with the number of freeze-thaw cycles. As the number of freeze-thaw cycles increases,the difference in kinetic energy released at different mining speeds also increases.
    Analysis on Gateway Improvement Control by Surrounding Rock Grouting in Complex Granular Roof
    ZHANG Jiyuan, REN Jinwu, XIN Yajun, ZHANG Pan, ZHANG Zengguang, WU Chunhao
    2024, 53(4):  228. 
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    The gateway with complex granular roof surrounding rock fails seriously with large deformation and difficult support. The paper analyzed the deformation damage characteristics and failure causes of surrounding rock with complex granular roof,studied the characteristics of slurry density,water extraction rate and fluidity of similar-paste grouting materials with different proportions,explored the influence mechanism of different ash-sand ratio and coal ash content on the strength of similar- paste grouting materials,and determined the optimal ratio of similar-paste grouting materials and reasonable grouting reinforcement support scheme. The results showed that gateway roof of complex granular surrounding rock was damaged seriously with mesh pocket sinking,overall intrusion and "concave" expansion deformation at high and low sides respectively. The main causes for the instability of gateway surrounding rock were granular block,weak cementation,high stress,soft coal and support failure. With the increase of ash-sand ratio and coal ash content,the water extraction rate and fluidity of slurry increased,while the slurry density decreased,and the influence of ash-sand ratio on slurry fluidity was greater than coal ash content. With the increase of ash-sand ratio and coal ash content,the failure strength of slurry grouts showed accelerated attenuation and sharp decline-slow increase-slow decline trend. The optimum ratio on the ash-sand ratio and coal ash content of similar-paste grouting materials were 0. 6∶1 and 80% respectively. After adopting the technical scheme of anchor (cables) + paste grouting control for 30 days,the maximum subsidence of the roof was less than 80 mm,the maximum convergence of two sides was less than 70 mm,and the gateway surrounding rock was stable.
    Strength Characteristics and Microscopic Mechanism of Bauxite Slime Treated by Guar Gum
    SHI Hangxiang, MENG Jianping, JI Jingru, YAN Rongtao
    2024, 53(4):  236. 
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    Biopolymers,as a novel environmentally friendly soil treatment and improvement material,have gained extensive applications in recent years,even in small quantities,due to their significant strengthening effect on soil. In this study,laboratory experiments were conducted on bauxite slime samples treated with different concentrations (0%,1%,1. 5%,and 2%) of guar gum. These experiments included testing for Atterberg limits,quick shear tests,nuclear magnetic resonance (NMR) experiments, and scanning electron microscopy (SEM). The experimental results indicate that with the increase in biopolymer content,both the liquid limit and shear strength of bauxite slime improved significantly. Specifically,the bauxite slime treated with 2% guar gum exhibited a 26% increase in liquid limit and a remarkable 182% increase in cohesion. NMR experiments revealed that guar gum could increase the moisture content of bauxite slime samples and create large internal pores within them. Additionally,SEM images confirmed the formation of a guar gum-bauxite slime matrix,thereby enhancing both the liquid limit and shear strength.
    Optimization of Drilling Pressure Relief Parameters in the Working Face of Shaiqihe Phosphate Mine
    WANG Qihu, ZHOU Junbao, YAO Nan, LUO Xiaobing, WU Meng, ZHANG Zhen, LING Jisuo, HUANG Zhaoyun
    2024, 53(4):  244. 
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    Rock burst is a major technical challenge that troubles the safe mining of the Shaiqihe phosphate mine. The pressure relief parameters of the borehole in the mine don't match the stress distribution of the surrounding rock,and the pressure relief effect needs to be improved. Taking the +80 m working face of the mine as the research object,numerical simulation is used to analyze the changes in stress and elastic energy of the surrounding rock of the excavation roadway under different borehole pressure relief parameters. The optimal pressure relief drilling parameter scheme is explored,and the Gu-Tao rock burst criterion is introduced,calculate the ratio of maximum principal stress to uniaxial compressive strength,evaluate the rock burst level before and after optimizing the pressure relief drilling parameter scheme,and verify the pressure relief effect of drilling. The research results indicate that as the drilling depth increases,the stress in the surrounding rock of the tunnel first decreases and then increases. When the drilling depth is 10 meters,the maximum tensile stress is the smallest;While maintaining the same number of boreholes,if the spacing between boreholes is too small,the pressure relief areas formed around the boreholes overlap,and the overall pressure relief range is limited. If the spacing between boreholes is too large,the pressure relief areas formed between each borehole cannot play a synergistic pressure relief role. When the spacing between boreholes is 1. 1 m,the maximum tensile stress is the smallest;The larger the drilling diameter,the smaller the stress concentration in the surrounding rock;After optimization,the maximum principal stress of the pressure relief drilling parameter scheme decreased by 14 MPa,and the risk level of rock burst decreased from moderate to no rock burst. The research results can provide reference for the selection of pressure relief drilling parameters in similar mines in western Hubei.
    Biodegradable and Antibacterial Nanofibrous Membranes for Long-Term and Low-Resistance Filtration of Airborne Particulate Matters
    WANG Zhirong, YANG Ting, KE Lü, HUANG Rongting, ZHU Jintuo, HE Xinjian, XU Huan
    2024, 53(4):  252. 
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    Coal mine dust,fine particulate matter (PM) in the air and the existence of pathogens,seriously harm the ecological environment and human health. Traditional polymer membrane filters have shown a great role in dust,filtering PM and pathogens. However,traditional polymer materials are not degradable,which can easily lead to plastic pollution and microplastic hazards. It is urgent to develop degradable fiber filtration materials with high filtration efficiency and high antibacterial efficiency. In this paper,titanium dioxide (TiO2) nanoparticles were directly embedded into polylactic acid (PLA) nanofibers (PLA @ TiO2) by a combination of electrospinning-electrospray technology. At the same time,the spinning environment humidity was regulated to form a beaded structure,which effectively improved the electrical activity,electret performance and filtration performance of the fibrous membrane and provided excellent UV shielding and antibacterial properties. When the airflow rate was 85 L/ min,the filtration efficiency of the pure PLA fibrous membrane for PM0. 3 was only 83. 9%,and the air resistance was 654. 9 Pa. The PLA@ TiO2 fibrous membranes filtration efficiency was improved,and the air resistance was significantly reduced. When the TiO2 concentration was 4%,the filtration efficiency was 97. 9%. The air resistance was reduced to 260. 2 Pa. In addition,the antibacterial efficiency of the PLA@ TiO2 membrane against E. coli and S. aureus reached 100%. TiO2 embedded in PLA fiber could also enable the fibrous membrane to absorb ultraviolet radiation,and the ultraviolet transmittance (TUVB) of the PLA@ TiO2 fibrous membranes was reduced to 20. 1% compared with pure PLA fibrous membrane,which could prevent and avoid skin injury and other diseases. The combination of nanofiber electret properties and beaded structure provides efficient filtration,low air resistance,and high bacteriostatic efficiency. It provides a useful reference for reducing and preventing the occurrence of pneumoconiosis.
    Study on the Performance and Environmental Effect of Alkali-Activated Fly Ash Based Copper Tailings Filling Paste Test Blocks
    SONG Baofeng, LI Heyu, WANG Li
    2024, 53(4):  262. 
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    In order to promote the sustainable utilization of mineral resources and protect the ecological environment of mines,a certain amount of alkali-activated fly ash was used to replace cement to prepare copper tailings filling paste. The strength,impermeability and environmental effects of copper tailings filling paste test blocks were evaluated by systematic mechanical, permeability and heavy metal precipitation tests. The mineral composition of cementitious materials and the microstructure characteristics of filling paste test blocks were analyzed by X-ray diffraction and scanning electron microscopy. The influence of alkali-activated fly ash on the comprehensive performance of filling paste test blocks and its microscopic mechanism were revealed. The results showed that alkali activation could significantly improve the activity of fly ash. Under the action of 1 mol/ L NaOH alkali activator,the compressive strength of 20% fly ash based copper tailings filling paste test blocks after 28 d curing was 17. 8% higher than that of cement cementitious test blocks,and the permeability coefficient was reduced by 68. 0%. The comprehensive cementation effect was remarkable. The addition of alkali-activated fly ash reduced the precipitation of heavy metals during the hardening process of copper tailings filling paste test blocks,which was helpful to control the pollution of groundwater resources. Using the filling effect of fine particles and the composite cementitious effect of fly ash,the porosity of copper tailings could be effectively reduced,and new hydration products could be formed to enhance the bonding force between tailings particles,thereby improving the strength and stability of the material.
    Experimental Study on Preparation of Lightweight Foamed Concrete by Low Silicon Iron Tailings
    HAN Housheng, LI Yubiao, PAN Mengzhen, CHEN Kun, ZHANG Yuan, GU Yunxiang, XUE Lutao, JIAN Shouwei
    2024, 53(4):  269. 
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    In order to solve the problem of large stock and difficult utilization of low-silicon iron tailings,lightweight foamed concrete was prepared by using low-silicon iron tailings from Yangjiawan tailings reservoir as mineral admixtures,cement as cementitious material and Al powder as foaming agent. The effects of cement dosage,water-to-material ratio,foaming agent Al powder dosage and activator CaO dosage on the performance of foamed concrete were investigated. The results showed that under the condition of iron tailings dosage of 55%,Al powder dosage of 0. 14%,CaO dosage of 5%,polypropylene fiber dosage of 0. 3%,foam stabilizer dosage of 0. 25% and water-to-material ratio of 0. 55,the lightweight foamed concrete with compressive strength of 1. 84 MPa,dry density of 768. 61 kg/ m3 and specific strength of 2. 394×10-3 Nm/ kg could be prepared after curing 28 days of constant temperature and humidity at 20±1 ℃. The comprehensive performance was good,which met the requirements of A08 dry density grade and C1 strength grade of JG/ T 266—2011 Foamed concrete. The mechanism analysis showed that the excessive increase of porosity would destroy the pore structure inside the products and had a negative impact on the strength of the products. The addition of iron tailings helped to mix the slurry,promoted the formation of Ca(OH)2,further created an alkaline environment for the slurry,and promoted the formation of hydration products such as ettringite and C—S— H gel. The interlaced distribution of these products and iron tailings would support the pore structure and improve the mechanical structure,so that the foamed concrete still showed good mechanical properties even at a low density.
    Optimization of Nickel Extraction from Nickel-bearing Copper Tailings Using Reduction Roasting-Magnetic Separation Process with Response Surface Methodology
    CHEN Xiaoting, XIAO Junhui, CHEN Zhengyi, LI Chengxiu
    2024, 53(4):  275. 
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    Aiming at the problems of low grade and complex mineral phase of a nickel-bearing g copper tailings,the nickel- copper tailings were pretreated by reduction roasting method with coke as reducing agent,NaCl,Na2CO3 and NaClO as the roasting additives. In order to improve the separation and enrichment index,the Box-Behnken response surface method was used to design the experiment and optimize the dosage of various additives in the reduction roasting of nickel-containing copper tailings. The influence of the interaction between the factors on the magnetic separation index was analyzed,and the mathematical prediction model between the independent variables and the response values was established. The optimal process conditions for reduction roasting-magnetic separation of nickel-containing copper tailings were determined :NaCl dosage 23. 723%,Na2CO3 dosage 14. 552%,NaClO dosage 10%. Under this condition,the predicted nickel grade of magnetic separation concentrate was 3. 528%. It has certain practicability and feasibility for optimizing the reduction roasting process of nickel-containing copper tailings