Nonferrous slag，a by-product of the nonferrous metal smelting process，can be used as a replacement for cement in the preparation of cementitious materials，which is a critical way to utilize large amounts of non-ferrous metallurgical solid waste resources.This study systematically analyzed to shed light on the latest research progress and achievements on the cementitious materials mainly prepared with the non-ferrous metallurgical slags both in China and abroad.Particularly，five aspects are emphasized in this paper，which are the composition and structural characteristics of nonferrous slag，potential cementitious properties，the activation method of slag，the preparation methods of cementitious materials，and the performance of its cemented body，respectively.The results showed as below：First，the mineral composition and structures of nonferrous slag differed widely.The crystallization of silicate mineral is almost complete and has high chemical stability，but the content of the vitreous body is lower.Second，the evaluation method of nonferrous slag potential gelling activity and the activity evaluation criteria are inconsistent.Third，the combination of phase modification and compound activation method could effectively improve the gelling activity of nonferrous slag.Fourth，nonferrous slag cementitious materials has good durability and high-temperature resistance and has certain properties of heavy metal solidification.At present，the preparation of cementitious materials based on nonferrous slag is mainly laboratory-based with few examples of large-scale industrial applications.The fundamental reason is that the problem of low and insufficient activity of nonferrous metallurgical slag has not yet been completely solved.As such，changing the structural characteristics of non-ferrous metallurgical slag is the key to overcoming the obstacles to its large-scale industrial utilization.Followed by this，the paper next discussed some important issues involved in the preparation process of cementitious materials and highlights the importance of the establishment of a non-ferrous metallurgical slag cementing system configuration database，the use of molecular research on simulation optimization of activation methods，and the development of simple and efficient activation methods，all in an effort to hasten the expansion of the future industrial application of non-ferrous slag cementitious materials preparation technology.
Copper and nickel slag is an industrial by-product produced by smelting copper-nickel metal in smelters，and it is an urgent problem to comprehensively utilize copper nickel slag and realize the development and utilization of high value-added products.The microcrystalline glass with good mechanical properties and high corrosion resistance can be prepared by using copper-nickel slag as the main materials and adding a small amount of composition regulator，clarifier and co-solvent in the process of production.Copper and nickel slag contains a lot of valuable metals，so it can be recovered by means of solution leaching，flotation extraction and high temperature reduction.In addition，the method of physical and chemical excitation of copper and nickel slag can be used to prepare mine filling green cementitious materials and high strength composite cementitious materials under the condition of mineral admixtures.Moreover，copper and nickel slag can also be used for concrete fine aggregate.The resource utilization of copper and nickel slag can save resources and protect environment.Compared with flotation and high temperature reduction method recovery to extract valuable metals from nickel smelting slag，the chemical solution leaching treatment method can comprehensively recover valuable elements and realize the cascade utilization.And the small amount of iron compounds after removing iron from copper nickel slag can be used as nucleating agent in the preparation of microcrystalline glass，which would be greatly improved the utilization rate of industrial copper nickel waste slag.In additon，combined with the new concrete technology is the key to solving the disadvantages of high density and low activity of copper nickel slag in the application of civil engineering.Therefore，further research is needed to fully utilize copper and nickel slag on a large scale.
The accumulation of solid waste such as tailings，smelting slag and mined-out areas caused by mining and smelting of mines has become the main problems in environmental protection，production and life safety in mining area.Typical pollution in mining areas includes lead-zinc，chromium，cadmium，manganese and arsenic pollution，which poses a great threat to groundwater，soil and health.Filling mining method is a new mining technology，which can not only effectively solve the problem of goaf collapse，but also immobilize the heavy metal by fill materials.At present，the reported studies mainly focus on the filling properties and gelation mechanism of filling cementitious material.However，the basic researches on the dissolution behavior and the immobilization mechanism of heavy metals are not enough yet.In this paper，the pollution features，dissolution behavior and migration mechanism of the typical contaminants in mining area，such as the lead，zinc，arsenic，chromium，cadmium，manganese and other harmful substances are presented.Through the ways of wastewater emission，atmospheric deposition，surface runoff，leaching，soil infiltration，the contaminant pollutes the atmosphere，water and soil around the mining area in the form of acid wastewater，waste gas or solid waste.The research progress on filling and immobilization of cementitious materials based on the solid waste from mining area，such as lead-zinc slag，blast furnace slag，chromium-containing slag，metal mine tailings are reviewed.The immobilization mechanism of harmful substances on the cementitious materials based on the solid waste from mining area is related to a series of physical and chemical behaviors，such as adsorption，precipitation，ions exchange，physical coating.However，the current study on the immobilization mechanism for harmful sub-stances on filling cementitious materials is not enough yet.Aiming at the present study and existing problems，prospects for the development of filling cementitious materials was put forward.The further study on filling cementitious materials could focus on the following aspects：Dissolution regulation and mechanism of heavy metals in tailings，smelting slag and cementitious materials，immobilization performance for harmful substances on cementitious materials based on solid waste，chemical composition，structure，reaction mechanism，relationship between product and solidified harmful substances，the effect on microstructure by harmful substance.This article could provide reference for the researchers and government officials for the development of filling cementitious materials.
The metallurgical and coal power industries produce a large amount of solid wastes，such as red mud and coal gangue，etc.The main elemental composition of this solid waste is Si，Al，Fe，Ca，Na and O，etc.It has the potential to prepare cementitious materials in terms of chemical composition and phase composition.The preparation of industrial solid waste into low cost cementitious material is an effective way to realize the large utilization of solid waste as well as energy conservation and emission reduction.Solid waste cementitious materials with 65% of red mud and coal gangue were prepared.Different mass ratios between red mud and coal gangue was considered.The recombination method of thermal activation and compound activation methods were used to improve their cementitious properties.X-ray diffraction（XRD），thermogravimetric-differential thermal analysis（TG-DSC） and Fourier infrared spectroscopy analysis were used to analyze the hydration products at different ages.The results show that the mass ratio of red mud to coal gangue has an important influence on the compressive strength of the hardened pastes，as well as the formation and development of hydration products.When the addition of red mud and coal gangue in the solid waste cementitious materials are 39% and 26% respectively，the compressive strength is the highest on the 3rd day，up to 13.28 MPa.When the addition of red mud and coal gangue in the solid waste cementitious materials are 13% and 52% respectively，the compressive strength on the 28 days is the highest，up to 31.62 MPa.The XRD patterns show that the red mud and coal gangue composites after thermal activated can react with gypsum，calcium hydroxide and carbonate to form ettringite （AFt），monosulfoaluminate hydrate （AFm），Hemicarbonate （Hc），and so on.TG-DSC analysis show that the content of C-A-S-H gel and AFt produced by different mass ratios of red mud and coal gangue is different.The pozzolanic reaction of the samples with higher coal gangue content is stronger at 28 days，resulting into the higher consumption of the calcium hydroxide in the activator，which is the main reason for the rapid development of the compressive strength of the red mud-coal gangue based solid waste cementitious materials at 28 days.A synergistic effect between red mud and coal gangue was determined by the heat activation and the addition of calcium based activators，i.e.， the release of active aluminate and silicate ions was promoted and the pozzolanic reaction was activited with more hydration products formed.Thus，it is conducive to the improvement of the compressive strength of sample in the early and late stages.This research provides theoretical guidance for the application of red mud and coal gangue-based bulk industrial solid wastes with higher aluminum and silicate components in the preparation of pavement base materials，wall building blocks and mine filling materials.
The copper nickel smelting slag is mainly the pyrometallurgical smelting slag discharged from the copper nickel ore in the smelting process.Its main elements are iron and silicon，with contents of about 40% and 30% respectively.Generally，the disposal of copper and nickel smelting slag is mainly stacking and landfill，which wastes land resources and pollutes the environment at the same time，so the comprehensive utilization rate is low.It has been shown that the copper nickel smelting slag has certain pozzolanic activity，and it is feasible to prepare filling cementitious materials with it.In this paper，copper and nickel smelting slag were ground to different fineness，cement mixed with smelting slag was used as cementitious material，Gobi aggregate was used as aggregate，and orthogonal test was carried out to prepare cementitious filler based on different grinding time，slag content and activator content of smelting slag.By measuring the uniaxial compressive strength of cemented backfill at different ages，the influence rule and mechanism of various factors on the compressive strength of cemented backfill were studied，and the final hydration products were qualitatively analyzed by SEM.The results show that with the increase of grinding time，the uniaxial compressive strength of cemented backfill increases at first and then decreases.The optimal grinding time is 50 min，corresponding to D（0.1），D（0.5） and D（0.9） of 4 μm，29 μm and 120 μm respectively.The addition of smelting slag reduces the uniaxial compressive strength of cemented backfill，but the reduction of compressive strength of backfill in the later period of maintenance is lower than that in the early period.The pozzolanic reaction of copper nickel smelting slag in cement Gobi aggregate system can promote the compressive strength of cemented backfill.SEM images show that the addition of Cu-Ni slag can promote the formation of ettringite and calcium silicate hydrate （C-S-H）.The influence of activator on the uniaxial compressive strength of cemented backfill is not obvious.The results of orthogonal test show that the content of Cu-Ni smelting slag has the greatest influence on the uniaxial compressive strength of cemented backfill， the second is the content of activator，and the least is the grinding time.Using copper nickel smelting slag with grinding time of 50 minutes，the ratio of the slag to cement is 2∶8，the content of activator is 4%，and the uniaxial compressive strength of cemented backfill is the highest.
With the further expansion of demand in the non-ferrous metal industry，the environmental pollution caused by large-scale stacking of copper-nickel smelting slag is becoming more and more serious.There are various forms of secondary utilization of copper-nickel slag in worldwide，including conventional methods such as metal extraction，glass-ceramics generation and ceramics，all of which have the disadvantage of low comprehensive utilization.Therefore，it is of great practical significance to study the construction cementitious materials using copper-nickel slag as the raw material in the secondary utilization of industrial waste.In the preliminary experiment，our research group used NaOH as the alkali activator to conduct the ion dissolution characteristics research of copper-nickel slag and the mechanical properties test of copper-nickel slag cementitious materials.The preliminary results show that the gelation and mechanical properties of copper-nickel slag materials are not ideal under the condition of a single alkali activator，and it is difficult to meet the actual engineering application standards.Therefore，this paper aims to use mineral admixtures to accelerate the activation of modified copper-nickel slag cementitious materials to improve their mechanical properties.After comprehensive consideration，we selected the slag powder and fly ash，which are also industrial waste，as the modifier.The admixture was mixed into the copper-nickel slag separately through the external mixing method to form two experimental groups.The final mixture ratio and water-cement ratio are adjusted and determined according to preliminary experiments.After curing，the compressive strength of each group of samples was tested by a universal testing machine.Then the product composition and modification mechanism of the experimental samples at various ages were analyzed by XRD，FTIR，SEM and other testing methods，and the performance improvement effect of different mineral admixtures was evaluated.The results show that both fly ash and slag powder as admixtures can improve the mechanical properties of copper-nickel slag cementitious materials of various ages by NaOH-activation，and the modification effect of high-doped slag powder is better.The modified cementitious material can basically replace ordinary Portland cement.According to the analysis of sample product and microstructure，the addition of mineral admixtures makes up for the deficiency of insufficient calcium source in the copper-nickel slag，which makes the polymerization reaction under alkaline activation more intense.In addition，the amount of C-S-H gel produced in the samples of the modified experimental group increased significantly，and the amount of iron gel produced decreased，showing a good acceleration excitation effect at all ages.
The deep exploration project of Yinshan copper polymetallic mine in Dexing，Jiangxi Province undertaken by Jiangxi No.4 Nonferrous Geological Exploration Team has achieved important exploration results. The newly proved resource reserves （331+332+333） are 540 000 tons of copper，230 000 tons of lead + zinc，57 tons of gold，914 tons of silver and 5.93 million tons of sulfur. It is equal to increasing the scale of a large copper mine，a large gold mine，a medium-sized lead-zinc mine and a near large silver mine. In this deep exploration，the original geological logging of more than 100 000 meters of drilling and more than 17 000 meters of tunnel has been carried out. 35 900 basic analysis samples have been taken and various rock and ore test samples matching with the exploration stage have been sent for inspection. In order to further expand the prospecting in the deep part of Yinshan，evaluate the prospecting potential in the deeper part of the mining area and predict the favorable space for ore generation，through the detailed geological observation and recording of various prospecting projects in the deep exploration，combined with the rock and ore test work，further systematically summarize the results of the exploration report，analyze and study the basic geological conditions and metallogenic characteristics of the deposit formation，so as to extract the results.The new understanding includes：（1）Yanshanian Yinshan subvolcanic body is closely related to mineralization，3# dacite porphyry is related to copper gold mineralization，5# quartz porphyry is related to lead zinc silver mineralization.（2）The altered quartz diorite in Caledonian period appears in many places on the outer side of the 3 Ying’an porphyry in Jiutong district，which，together with sericite phyllite and blasting breccia，forms the ore bearing surrounding rock in the Ninth-Xishan district.The opened magmatic activity channel is favorable for the emplacement of the 3 rock body related to the mineralization in Yanshan period.（3）The two flanks of Yinshan anticline are associated with the fracture structure belt，which is the main ore controlling structure.The northwest wing is associated with the East-West fracture structure belt，which is extremely developed with a wide strike and a long extension length. The south-east wing develops the North-South fracture structure belt，which is characterized by a short strike and a scattered distribution，which results in the north-west wing of Yinshan anticline controlling the occurrence and distribution of most ore bodies.（4）The location and shape of the orebody are directly controlled by the main fault and its associated network fractures on both sides. The sulfide vein continuity in the main fault controls the continuity of the ore body. The fine network vein ore is the main mineralization type，and the thick and large ore bodies are often composed of several main fault surfaces close to each other，such as the Ninth-Xishan District copper ore body.（5）The hydrothermal alteration associated with mineralization is a low-temperature alteration combination mainly composed of sericitization，carbonation and chloritization，which is lack of high-temperature potassium silicate salinization of porphyry deposits.The deep orebody of Yinshan copper polymetallic mine has not been closed，especially the outer contact zone on both sides of the deep 3 Ying’an porphyry at the turning part of Yinshan Ninth-Xishan area and the deep part of known orebody inclined extension are the best direction for subsequent ore prospecting.
The Qianchuiliu mining area of Muping in Yantai City is located in the northeast margin of Jiaolai Basin，Shandong Province.It shows good location and metallogenic condition with Liaoshang gold deposit （super large） on the west and Xilaokou gold deposit（large） and Xijingkou gold deposit（medium） on the east.However，there has been no breakthrough in ore prospecting in this area through geological work for many years，and the prospecting has fallen into confusion.In this paper，base on the introduction of the geological background of the Qianchuiliu mining area，we sorted out and summarized the geological，geophysical and geochemical data obtained in this area.Then based on the characteristics of the surrounding typical gold deposits and the main orebodies in each deposit，we summarized the gold metallogenic regularity and the metallogenic characteristics in this area.According to above studies，the reasons why the prospecting effect is not obvious in this area in the past are found and discussed.It is considered that there are some problems，including the selection of geophysical methods，excessive engineering spacing，too much attention to the industrial grade of surface samples，and lack of systematic understanding of mineralization.Furthermore，two possible prospecting ideas were proposed：Firstly，it is considered that the four gold mining areas，e.g.，Liaoshang，Qianchuiliu，Xilaokou and Xijingkou are controlled by the same NE-trending large fault zone from west to east，the inclination angle gradually changed from steep to gradual；Secondly，the above four mining areas are controlled by a large fault zone in the east-west direction，the inclination angle gradually changed from steep to gentle from north to south.Gold orebodies exists in the large fracture zone，the shallow orebody is characterized by steep dip，scattered and small scale.Whereas，the deep orebody mainly exists in the fault fracture zone from steep to slow，distinguished by large scale and stability.Notably，there is a large ore-free interval between shallow and deep ore bodies.Further analysis shows that in the Qianchuiliu mining area between Liaoshang and Xilaokou，although there are no industrial orebodies on the surface or shallow surface，a large-scale fracture zone has been found，which should be brought into the same metallogenic system as the surrounding gold deposits.No matter which model controls the ore deposits，in NE or near EW direction，it is inferred that there are a series of gold orebodies in Qianchuiliu mining area，which are relatively gently dipping and inclined to SE or S，and exist in the place from steep to gentle in the fracture zone.Therefore，the gold resource potential is between the Liaoshang and Xilaokou gold deposit，and it is concluded that there is a great prospecting potential.
Tongdao county is located in southwest of Xuefeng arc structure belt，there are some small and medium-sized gold deposit such as Jinkeng deposit，Huanggou deposit and Chaxi deposit.Few research have done in this area，in order to discuss the genesis of gold deposit，this paper focuses on the genetic mineralogy study about pyrites of different occurrence.The macroscopic geological characteristics of the three deposits show that the wall rocks of the ore body are all low-grade metamorphic sandstone slate.Strong silicification alteration and fading alteration occurred in the surrounding rocks near ore-bearing quartz veins in Jinkeng mining area.The dip angle of quartz vein is steep in Huanggou mining area，and the tendency is southeast or northwest，the fracture filled with quartz vein is shear fracture.The ore bearing quartz veins in Chaxi mining area are mainly NW steeply dipping veins and their branch gently dipping veins.The gold orebodies are mainly quartz vein type or altered rock type.The ore contains pyrite，arsenopyrite and other sulfides.Generally，the ore vein with more pyrite content has a relatively high gold grade，suggesting that pyrite is the main gold-carrying mineral.Rock-mineral determination show that pyrite is mainly cubic and pentagonal dodecahedron and other semi automorphic granular in three gold deposit.MLA（mineral liberation analyzer） scanning results show that gold was produced in pyrite farcture or pyrite intergranular in Huanggou gold deposit.Major element results analyzed by EPMA show that the pyrites in general are rich in iron and deficient in sulfur，containing a small amount of arsenic.The δFe-δS diagram shows that all points from three deposit concentrate in a narrow range，which is consistent with metamorphic hydrothermal gold deposit.Trace elements results analyzed by LA-ICPMS show that average Co/Ni value for Jinkeng pyrite samples is less than 1，which implies the fluid are from metamorphic water mainly.There are two kinds of pyrites in Huangou deposit，one produced in fine quartz vein，the Co/Ni value is near 0，the other zonal pyrite produced in wall rocks near ore，the Co/Ni value of core and edge are quite different，which implies the zonal pyrites have multi-stage growth history.As-Co-Ni diagram show that pyrites from Jinkeng and Huanggou deposit are mainly metamorphic hydrothermal type，and the metallogenic temperature should be medium low temperature.Compared with that of Huanggou gold deposit，pyrites collected from Jinkeng deposit has higher trace element content（e.g.，Au，Ag，Cu，Pb and Zn），which suggests that the Jinkeng area has more better prospecting potential.According to less private mining，we infer the gold body are eroded slightly，there is still great prospecting in deep part of the deposit.
The upward horizontal slicing and filling mining method is adopted in No.1 sub roadway of -750 m middle section in Jiaojia gold mine.Due to the development of layered joints on the roof and staggered distribution of joint structures，wedge-shaped caving and spalling failure of the roof occur.It is difficult to control the stability of rock mass with traditional bolt support.In this paper，through the field engineering geological survey and rock mechanics experiment，the rock mass quality grade is determined to be grade Ⅳ.The composite support system of resin anchor cable，metal mesh and shotcrete were selected by stability chart method，and the reasonable structural parameters of resin anchor cable support were calculated theoretically.Through the industrial test in -750 m middle section，the practical results show that the stability of rock mass has been significantly improved after using resin anchor cable support system.Through field displacement monitoring，the safety，reliability and effectiveness of resin bolt support system are further verified，which provides strong technical support for mining body under deep complex structure and accumulates certain practical experience.
Sanshandao gold mine，belonging to Shandong gold mining （Laizhou） Co.，Ltd.，is located at Laizhou Bay of the northwest of Jiaodong Peninsula，Shandong Province.The surface of gold mine is covered by river，sea，roads and village，so Sanshandao gold mine is a typical three-underground mine.The purpose of this paper is to optimize the technology and control measures of the “three-underground” mining mine.Through analysis of “three-under” mining case of Sanshandao gold mine， the mining technical conditions was analyzed through investigation， simulation and monitoring methods， and the impact of “three under” mining on the surface was analyzed combined with the relevant parameters of the filling method.The main research objects are protected top pillar and mining sequence.The method of room and pillar alternately raised mining with backfill could reduce rate of ore loss.The rate of ore loss was reduced from 13% to 4%，which demonstrated the suitability of the method.Mining sequence is another object that influence mining safety and stability.Four mining plans were conducted by simulation models：Mining sequence of plan-1 was mining from one side to another；Mining sequence of plan-2 was mining from center to sides；Mining sequence of plan-3 was mining one every the other two panels；Mining sequence of plan-4 was mining from sides to center.Finally，the optimized mining sequence is plan-3.Fault was the major factor in mining safety，and F3 fault in Sanshandao gold mine have leaded to several water inrush accidents，so roadway engineering should keep away from F3 fault.But some roadways have to go through the F3 fault in reality.The first measure was reinforced the fracture zones by advance grouting.And put some pipes into the fracture zones in order to improve the engineering geological condition.For surface water body，the patrol system and emergency plan were set for prevent intrusion.In Sanshandao gold mine，345 GPS monitoring points were set to monitor surface deformation.The cover range of monitoring was 8.5 km2.The mining engineering influence was minimized to surface subsidence which showed the technology and measures were effective.In underground mining，IMS micro-seismic monitoring system was set in Sanshandao gold mine in 2012.A set of system of working in real time，dynamically，automatically was built for ground pressure monitoring.This system provided support for mining engineering safety and efficient.The mining engineering was also implemented based on principle of production-learning-research combination.Appropriate mining technical scheme and controlling measures are the guarantee of mining stability and sustainability.
With the implementation of the grand western development program，a number of mines located at high altitude have appeared in China，where the special environmental factors of low air pressure and low temperature have brought challenge to the dust extraction work of the mines.The large amount of productive dust will cause serious damage to human respiratory system and is one of the main threats to the health of mine workers.The working face of the excavation roadway is one of the largest productive dust sources in underground mining operation.Therefore，it is of great engineering value and theoretical significance to study the dust extraction method of excavation roadway in high-altitude mine.In order to optimize the ventilation method of dust extraction in an excavation roadway of high-altitude mine and study the law of dust particle diffusion and distribution，the numerical simulation was conducted with computational fluid dynamics software Fluent and an excavation roadway （with section shape of three centered arch） at an altitude of 3 700 m in Pulang mine was taken as research object.The Lagrange discrete phase model was selected to calculate the gas-solid flow，which allows the exchange of momentum，mass and energy between continuous phase and discrete phase but ignores the interaction between particles.Through analyzing six different ventilation scheme models about far-forcing-near-exhausting（FFNE），near-forcing-far-exhausting（NFFE） and pure forcing（PF） established in this paper，the airflow field，dust particle distribution and respiratory zone dust particle concentration of them were analyzed and compared to optimize the better ventilation method.The distance between the pressure vent and the heading face and the distance between the center of the air duct and the ground were set as parameters to optimize the position of the air duct of the blowing ventilation.The mass concentration of dust particles and the law of dust particle diffusion in the selected plan were analyzed and compared with the excavation roadway in plain mine under the same ventilation condition.The following conclusions can be drawn：For the excavation roadway at an altitude of 3 700 m in Pulang mine，the best solution for dust extraction is using blowing ventilation scheme where the air duct is arranged in the position directly above the center of the roadway，while the distance between the pressure vent and the heading face is set to 16 m， and the distance between the center of the air duct and the ground is set to 3 m.The sedimentation of dust particles makes the mass concentration of dust particles is high at the bottom of the roadway and low at the top of the roadway.The mass concentration of dust particles at the cross section of the roadway （1 m，5 m，10 m，20 m，30 m） increases first and then decreases.The occurrence point of the maximum value of the dust particle mass concentration moves away from the working face with time，and its value generally decreases.Under the same ventilation condition，the dust extraction efficiency of high altitude mine is better than that of plain mine.
Mineral resources are an important pillar of China’s development.Industries based on mineral resources occupy half of the national economic development.However，with the long-term exploitation of mineral resources in China，many mines have encountered various production and safety issues.Poor resource conditions，aging production equipment，poor management capabilities，and many safety accidents have brought problems to the development of China’s mines and have become a huge hidden danger.In recent years，with the rising demand for healthy and safe mine environment in China’s mines，the relationship between safety guarantee conditions and the production capacity of mines has become closer and closer.The optimization of mine safety guarantee conditions and the scientific and rational formulation of production capacity targets becomes particularly important.Based on the characteristics of the production capacity of underground metal mines，this paper establishes the “human，machine，material，environmental，and pipe” safety guarantee research and evaluation model of underground metal mines related to production capacity through the methods of literature survey，field investigation，and expert interviews.The calculation characteristics of the model calculation process were designed and demonstrated by comprehensively utilizing the calculation characteristics of entropy weight-analytic hierarchy process，accident tree and LEC method.Finally，taking an underground lead-zinc mine in China as an example，the research was conducted from three aspects，including the research on calculation and evaluation of the current safety assurance status score under the existing production capacity，evaluation and result verification of the ability to complete different production targets under current security conditions，and production capacity target formulation in the next 3 years.The evaluation results show that under the existing production conditions，if the mine want to rapidly improve the safety guarantee conditions，it is necessary to prioritize the reduction of the number of underground operators，reduce the violation rate of the operators，reduce the length of underground operations，optimize the conditions of underground mining，and rationally optimize the mining structure，and so on；The mine’s optimal production targets from 2020 to 2022 should be located at about 138 000 t/a，137 000 t/a，and 133 000 t/a，respectively.The comparison between the evaluation results and the facts proves that the evaluation results are consistent with the actual situation of the mine and can provide reference and guidance significance for the actual production of the mine.Therefore，the evaluation method can provide an effective basis and direction for mine capacity optimization，self-evaluation and improvement of safety guarantee capabilities.
The senior executives’ tenure is often regarded as a reflection of their power，cognition，experience，innovation and change attitude，which plays an important role in the management of senior executives and profoundly affects the operating efficiency of an enterprise.Most of the existing studies believe that there is a positive correlation between the two，but few studies examine the impact of current senior executives’ tenure on corporate operating efficiency from the perspective of China’s private mining enterprises，combined with the status of enterprises’ executive selection and operating management.Taking the financial data of 52 private mining enterprises listed in Shanghai and Shenzhen A shares as a sample，this paper measured the operating efficiency of them from 2013 to 2018 by using super-efficiency BCC model，and then maked an empirical analysis of the relationship between senior executives’ tenure and the operating efficiency of China’s private mining enterprises，also examines the moderating effect of senior executives’ post experience richness and equity concentration on the relationship.Based on the input-output perspective，this paper firstly selected total operating cost，net fixed assets，and employee compensation as input variables，total operating income and net profit as output variables，and used the super-efficiency BCC model to measure the operating efficiency of China’s private mining enterprises.The results show that：On the whole，the operating efficiency of China’s private mining enterprises is generally not high during the period of 2013 to 2018，with an average value of 0.682；The change trend of overall operating efficiency of enterprises shows a U-shaped distribution that first decreases and then increases.Specifically，the average number of enterprises whose operating efficiency needs to be improved urgently （that is，the value of operating efficiency is less than or equal to 0.6） is about 21 per year，accounting for 40.38% of the total sample size，while the average number of DEA efficient enterprises is about 3 per year，accounting for 5.77% of the total sample size.When discussing the impact of senior executives’ tenure on the operating efficiency of China’s private mining enterprises，an empirical analysis model of the relationship between senior executives’ tenure and the operating efficiency of China’s private mining companies，as well as a moderating effect model of senior executives’ post experience richness and equity concentration on the relationship between the two is constructed by taking corporate operating efficiency as dependent variable，senior executives’ tenure as independent variable，senior executives’ post experience richness and equity concentration as moderating variables，enterprise scale，enterprise listing age，asset-liability ratio，and heterogeneity of senior executives’ tenure as control variables.The results show that：（1）The senior executives’ tenure has a significant negative impact on the operating efficiency of China’s private mining enterprises；（2）The senior executives’ post experience richness and the equity concentration have a significant weakening effect on the negative relationship between senior executives’ tenure and the operating efficiency of China’s private mining enterprises.According to the empirical conclusions，this paper puts forward specific suggestions that are conducive to improving the management and operating efficiency of private mining enterprises.
The particle size of the grinding products in the fine grinding section of a domestic mineral processing plant is uneven，and there are more coarse-grained and over-fine-grained grades.At the same time，the content of the grinding fineness -0.074 mm does not meet the standard.According to the current mill grinding process，combined with the nature of the ore itself in the concentrator，the grinding quality is improved through the grinding process.This paper uses the international standard sieve for particle size screening of the ore sampled uniformly，combined with the spherical diameter semi-theoretical formula to formulate the grinding plan，compare the grinding results，evaluate and select the best grinding plan.Laboratory test results and data analysis show that the grinding media system is Φ45×50∶Φ35×40∶Φ30×35∶Φ25×30=30∶20∶20∶30. Compared with the steel ball plan and the current plant plan，the overall steel section plan has an over-coarse level of 0.10 mm and a yield reduction of 0.73 percentage points and 5.42 percentage points，respectively，and an over-pulverization level of 0.010 mm and a yield reduction of 2.51 percentage points and 0.77 percentage points，respectively.The grinding fineness -0.074 mm content has increased by 1.75 percentage points and 5.33 percentage points respectively.The intermediate easy-selection grade 0.100~0.038 mm yield has increased by 1.96 percentage points and 5.57 percentage points，respectively，and the grinding technology efficiency has been improved by 3.54 percentage points and 8.14 percentage points，mill q-200 increased by 3.15% and 10.24%.According to the comparison of various grinding indexes，it can be concluded that the grinding method of the steel section in the grinding process is mainly based on the grinding and peeling effect，supplemented by the impact effect，which can effectively reduce the content of coarse-grained and super-fine-grained grades，and improve the qualified grain.The level of content reduces the difficulty of flotation.The increase of the efficiency of grinding technology shows the improvement of the quality of grinding products，and the increase of the mill q-200 shows the improvement of the production capacity of the mill’s unit effective volume.The above conclusions indicate that the steel segment is more suitable for fine grinding process，it improve the quality of grinding products，the production capacity of the mill and the efficiency of the enterprise.
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