Nanobubbles are also called submicron bubbles or ultra-fine bubbles. As a gas cavity struc‐ ture with nanoscale，its unique physical and chemical properties and stability mechanism have been scientif‐ ically explained by systematic demonstration. In order to study the unique physical and chemical properties of nanobubbles in detail，aiming at the problems of difficult separation of fine-grained minerals，low effi‐ ciency of sewage treatment such as mine wastewater and low utilization rate of tailings resources，the appli‐ cation status and mechanism of nanobubbles in mineral flotation，sewage treatment，slag soil improvement and other fields were studied and analyzed. Analysis and research show that nanobubbles not only have ex‐ traordinary stability and efficient mass transfer characteristics，but also can produce characteristic products such as reactive oxygen species（ROS）through interface effects. The great potential of nanobubbles in pro‐ moting the sustainable development of green economy and high-tech industries in the future is reasonably prospected.

In order to explore the innovative application of 3D printing technology in the mining field， the development，classification，materials and mature application experience in various fields of 3D printing technology are sorted out.In view of the lack of experience in the application of 3D printing technology in the field of mines，it is difficult to promote the application and face many challenges. The applicability of 3D printing technology in the field of mines and the existing problems are systematically studied. The applicabil‐ ity and advantages of 3D printing technology in mining equipment parts manufacturing，mine model mak‐ ing，mine tool customization，mine resource recycling and other aspects are analyzed. The problems of tech‐ nical limitations，high cost，shortage of professional and technical personnel，low enterprise cognition and acceptance in the application of 3D printing technology in the field of mines are clarified. The development ideas and suggestions for promoting 3D printing technology in the field of mines in China are put forward.It is feasible and promising to promote the application of 3D printing technology in China's mining field. Com‐ pared with the traditional construction method，this technology has great advantages，but it needs the joint efforts of all parties to overcome the existing challenges，so as to promote the technological upgrading and in‐ novative development of the mining industry.

The blasting cost accounts for about 30% of the mining cost of open-pit mines，and the blasting quality will significantly affect the subsequent loading，transportation and crushing costs.Therefore， it is of great significance to reduce the blasting cost for mining enterprises.Through in-depth analysis of the current status of China's blasting operation cost management，there are problems such as weak cost manage‐ ment awareness，poor management level and imperfect supervision mechanism. At the same time，the influ‐ encing factors and difficulties of blasting operation cost control are analyzed in detail.On this basis，the key measures of blasting cost control are summarized，including the optimization of blasting design parameters， the application of intelligent blasting technology and the effective management of the cost of civil explosives. Finally，the future development trend of the blasting industry is prospected，and it is pointed out that the blasting technology innovation is still the core measure to control the blasting cost，especially the intelligent blasting technology. With its significant advantages in improving efficiency and precise control，it will be‐ come the dominant direction of the future development of blasting engineering technology.

Due to high static load，complex overburden space structure and violent roof movement， the large mining depth island working face is easy to induce rock burst accidents when it encounters dynam‐ ic load disturbance or geological structure change，which seriously threatens the safe mining of working face. In order to prevent the occurrence of rock burst accidents，the passive CT wave velocity inversion is carried out for the effective microseismic events in different mining stages of the 1310 large mining depth island working face by using the microseismic monitoring system and the passive CT inversion technology. Then， the inversion results are combined with the impact risk assessment model to predict the impact risk area of the working face. The prediction results show that the coal strata in the detection area are generally in the middle impact risk level，which is basically consistent with the actual situation. The application results show that the passive seismic wave CT inversion technology combined with the impact risk assessment model can effectively predict the potential impact danger zone in the surrounding area of the working face，and provide scientific guidance for the next stage of pressure relief and impact prevention measures and provide effective guarantee for the safe mining of the working face.

In order to solve the problem of mine shaft deflection and improve the stability of the mine， taking the main shaft and auxiliary shaft of Yingpanhao Coal Mine as the research object，based on the anal‐ ysis of the geological conditions of the mine，a simple and convenient steel wire cycloid measurement tech‐ nology is proposed. The plane coordinate system of the suspended datum line is determined by the method of traverse measurement，and then the shaft coordinate of the monitoring point position can be determined ac‐ cording to the coordinate of the steel wire，and the continuous and stable monitoring of the shaft deflection is realized. According to the analysis of the time and space characteristics of shaft deflection，it is found that the deflection of shaft has experienced three stages of rapid growth，deflection mitigation and stability. The main well and auxiliary well are affected by the underground goaf，and the deflection in the east-west direc‐ tion exceeds 300 mm，which is dangerous. Through the single hole multi-layer grouting correction technolo‐ gy，the effective correction of shaft deviation can be realized，and the deviation of the main shaft in the east�west direction is reduced by 21.7%，and the deviation in the north-south direction is reduced by 2.1%. The deviation of the auxiliary shaft in the east-west direction is reduced by 27.7%，and the deviation in the north-south direction is reduced by 87.8%，which improves the stability of the shaft and has great applica‐ tion and promotion value.

In order to improve the safety of underground fully mechanized mining with coal pillarless， the geological conditions of extra-thick hard roof in Shaping Coal Industry are taken as the engineering veri‐ fication object，and the geological area division is carried out after the exploration of the geological condi‐ tions of the working face. Combined with the underground geological characteristics，the underground blast‐ ing pre-splitting scheme，the constant resistance large deformation anchor cable support scheme and the un‐ derground gangue retaining support scheme are analyzed in depth，and a set of relatively complete non-pil‐ lar mining technology scheme under the extra-thick hard roof is formed. Through the underground industrial test and monitoring，the application reliability of the scheme is proved. According to the practical applica‐ tion in underground coal mine，it is shown that the three-zone pre-splitting blasting technology can reduce the hanging length of the roof during the operation and ensure the safety of the retained roadway. For under‐ ground support，it is necessary to combine different geological conditions to set up advanced support，post�frame support，temporary support and stable support respectively. Through different support schemes，the support efficiency and support economy of underground roadway can be improved. The fully mechanized mining technology without coal pillar under the underground hard roof can significantly shorten the pressure step distance and reduce the pressure intensity，which has a strong guiding effect for the efficient and safe mining of coal under similar geological conditions.

After decades of mining in a tungsten mine，the mining work in the middle section above -110 m has been nearly completed，but a large number of complex goafs have been left，which has brought hidden dangers to the mining of ore bodies and the safety of underground workers. In view of the stability of the upper multi-layer goaf，the field investigation and rock mechanical property test of the goaf are carried out. Combined with 3DMine and Midas GTS NX software，the stress，displacement and plastic zone distribu‐ tion of the surrounding rock are analyzed by FLAC3D finite difference method. The results show that the dis‐ placement value of F11 vein in 207# ~208# exploration line F11 in the middle section of +40 m and +190 m changes relatively large，and the stress concentration phenomenon is obvious，which is a dangerous area of collapse. In the middle section of + 190，+ 140，+ 90，+ 40，-10 m，204# ~ 207# line No.1 ore vein pillar pillar plastic zone distribution range is larger，almost through the whole pillar，is a dangerous area. Accord‐ ing to the research results，it is proposed to increase the displacement monitoring in the east-west vein group located in the 207# ~208# exploration line in the middle section of + 40，+ 190 m，and increase the stress monitoring in the middle section of + 190，+ 140，+ 90，+ 40 m in the middle section of 204# ~207# ex‐ ploration line No.1 ore vein pillar，and select the key area to implement the treatment measures，so as to pro‐ vide strong support for the safety management of the mine and the future mining work，and promote the sus‐ tainable development of the mine.

Artificial roof cutting is often used in coal mines to reduce the influence of mining on road‐ way stability under complex geological conditions. Therefore，it is particularly important to determine rea‐ sonable artificial roof cutting parameters. Based on the geological conditions of F6218 fully-mechanized cav‐ ing face with thick and hard roof in Buliangou Coal Mine，the reasonable roof cutting height should be 45~ 67.5 m and the roof cutting angle should be greater than -6.63 ° through theoretical calculation. FLAC3D is used to simulate the stress distribution law of roadway surrounding rock under different roof cutting heights and angles of F6218 main transport crossheading. The results show that when the roof cutting height is 52 m and the roof cutting angle is -5°，the roof of the working face can be smoothly cut off，and the internal stress distribution of the roadway protection coal pillar is low and uniform，which obviously achieves the effect of roof cutting and roadway protection，and the influence of the roof cutting height on the roof cutting effect is more obvious than that of the roof cutting angle. The field monitoring shows that there is a certain range of elastic area in the middle of the coal pillar，and the deformation of the surrounding rock of the F6225 auxilia‐ ry transport roadway is fast and stable. The deformation is within the controllable range，and the effect of roof cutting and roadway protection is remarkable.

Restricted by many factors such as coal seam occurrence conditions and dense roof and floor strata，the 4# coal seam mined in Wangjialing Coal Mine has the characteristics of high gas content， low coal seam and poor permeability. The drilling gas extraction efficiency is low，the attenuation speed is fast，and the gas extraction standard period is long. Therefore，taking the 18109 working face of Wangjialing Coal Mine as the research object，in order to improve the gas extraction efficiency of the working face trans‐ portation channel，it is proposed to use the hydraulic fracturing technology to pre-crack the area and then extract. The numerical simulation study is used to determine that the effective fracturing radius of 4# coal seam is 4.1 m under the water pressure of 20 MPa for 25 min. Based on the numerical simulation results，the fracturing measures are formulated and the effect is investigated. The results show that the attenuation rate of gas extraction concentration in 4# coal seam is 25% after 60 days of fracturing，and the extraction standard period is shortened to 7 days，and the fracturing effect is remarkable. Comprehensive analysis shows that hy‐ draulic fracturing technology can effectively improve the permeability of coal seam and improve the extrac‐ tion efficiency，which has certain positive benefits for gas extraction in low permeability coal seam.

In view of the geological conditions and mining needs of a gold mine in Minxian County， Gansu Province，a mining scheme is proposed to improve mining efficiency，reduce costs，ensure operation safety and reduce environmental impact. The geographical environment，ore body occurrence and mining technical conditions of the mine are comprehensively summarized，and the geological characteristics，hydro‐ geological and engineering geological conditions of the ore body are clarified. Through the systematic rock mechanics parameter test，it provides a scientific basis for the design of mining methods. Using FLAC3D nu‐ merical simulation，the numerical calculation model is established，the displacement law of stope and the evolution process of mining stress are analyzed，and the recommended mining scheme is determined. Two main mining schemes of surface unnatural collapse and surface natural collapse are proposed，comparison of structural parameters，mining and cutting engineering，drilling and blasting，ore filling，stope ventilation and pillar recovery are compared. Finally，according to the mechanical properties of rock，mining cost，safe‐ ty requirements and environmental impact and other factors，the most suitable mining method is recommend‐ ed，and the selection of support technology is proposed.

In order to solve the ventilation problems such as air leakage in the upper subsidence area of the south southwest wing of Ekou Iron Mine and the coordinated operation imbalance of multi-stage fans，the ventilation system is optimized to improve the effective air volume rate of the mine and ensure safe and effi‐ cient mining. The node wind pressure balance technology is used to optimize the critical path wind resis‐ tance，and the air volume distribution is adjusted in combination with the combined ventilation of the main and auxiliary multi-fans. A main-auxiliary combined ventilation method based on wind pressure balance is proposed to realize the coordinated operation of multiple fans in series and parallel. A three-dimensional ven‐ tilation model with air leakage path in subsidence area is established to dynamically match the air volume of each middle section. Through real-time wind speed monitoring and intelligent control，the air leakage node tends to zero wind pressure state，and the air leakage effect is suppressed. The field application shows that the effective air volume in the optimized mining area is increased from 75.25 m3 /s to 77.42 m3 /s，with an in‐ crease of 2.9%. The air leakage in the upper caving area decreased from 50.21 m3 /s to 4.24 m3 /s，with a de‐ crease of 93.4%，which significantly improved the effective air volume efficiency of mine ventilation. The technical system effectively solves the problem of air leakage in complex caving areas and optimizes the coor‐ dinated operation of multiple fans through pressure balance control, air flow collaborative distribution and fan dynamic adaptation, which provides an important reference for similar mine ventilation system optimization.

Under the condition of IV-level broken marble roof of ZnV3 ore body in a lead-zinc mine， when the two-step stoping method of stage open stoping with subsequent filling is applied，the problems such as roof and side collapse exposed in the I-step stope and unreasonable mining preparation project pose challenges to the safe stoping in the II-step stope. Therefore，the systematic optimization design of the II�step stope is carried out. The key points of optimization include stope structure parameters，mining prepara‐ tion engineering layout，roof and side support scheme and blasting and ore falling process. Through industri‐ al test verification，the optimized mining method significantly improves the stability and operation safety of the stope roof，and effectively controls the ore dilution loss rate within 15%.This optimization scheme effec‐ tively solves the problem of safe and efficient mining of the II-step stope under the condition of broken roof, and has the value of popularization and application in similar mine.

In order to study the influence of different fan blade angles on the performance of coal mine ventilator，the physical model of fan is established，and the structure of fan blade is designed. The orthogo‐ nal test method and finite element analysis method are used to study the FBD No.8.0 coal mine fan used in Jinxinda Coal Industry. The fluid simulation software Fluent is used to build the fan model，and the influ‐ ence of blade angle on the performance of fan is numerically simulated. The simulation results show that there is eddy current structure in the internal flow field of the fan，the internal energy loss of the blade is small，and the total entropy output value of the wing angle structure bladeis reduced by 2.15%. When the relative installation angle of the first stage blade of the fan is 75%，the maximum pressure of the wing angle blade increases by 21.19%.When the relative installation angle of the secondary blade is 25%，50% and 75%，the pressure is increased by 2.5%，9.6% and 8.4% compared with the prototype blade.It can be seen that by adjusting the blade installation angle，the fan pressure can be increased and the air volume per unit time of the fan can be increased，so as to achieve better ventilation effect.

In order to improve the resource utilization rate of a high-phosphorus oolitic hematite，a roasting-magnetic separation-leaching process for iron extraction and phosphorus reduction was proposed in view of the complex symbiotic relationship between iron minerals and phosphorus minerals and the diffi‐ culty in efficient utilization of conventional beneficiation methods. The experimental process conditions were optimized in the process of grinding-magnetic separation and sulfuric acid leaching dephosphoriza‐ tion. The test results show that under the conditions of grinding fineness of -0.038 mm95%，magnetic field strength of 95.54 kA/m，sulfuric acid dosage of 0.2 mol/L and reaction time of 20 min，the iron concentrate with total iron grade of 64.43%，total iron recovery of 96.54%，phosphorus grade of 0.18% and yield of 85.17% was obtained by the whole process test，which can provide guidance for other high phosphorus iron ore to increase iron and reduce phosphorus.

A porphyry copper-molybdenum ore in Heilongjiang contains 0.410% copper and 0.012% molybdenum. In order to comprehensively recover valuable elements such as copper and molybdenum，the ore dressing test was carried out in view of the characteristics of fine grain size of copper minerals，high content of bornite and high content of mud gangue. The test results show that the copper and molybdenum metals are recovered by copper-molybdenum iso-floatability-enhanced copper flotation recovery and mid‐ dle ore regrinding and reconcentration process. The copper grade of the iso-floatable copper-molybdenum mixed concentrate is 26.24%，the molybdenum grade is 0.71%，and the copper and molybdenum recovery rates are 78.81% and 71.83%，respectively. The copper grade of the enhanced copper flotation concentrate is 15.02%，the molybdenum grade is 0.16%，and the recovery rates of copper and molybdenum are 7.08% and 2.54%，respectively，which effectively improves the concentrate grade and recovery rate.

In order to reduce the fluctuation of grinding powder particle size of graphite raw materials and improve the recovery rate of fine powder，the response surface test is carried out.The results show that the classification frequency，the main machine frequency，the interaction of main machine classification and the interaction of feeding main machine have a significant effect on the fine powder particle size d50 of raw material grinding powder，and the degree of influence decreases in turn. The degree of influence on the recovery rate is the main machine frequency > classification frequency > induced draft frequency，and the interaction between the factors is weak.The optimized process conditions are as follows that feeding fre‐ quency is 9 Hz，main machine frequency is 19.7 Hz，classification frequency is 10.5 Hz，and induced draft frequency is 25 Hz. Under these conditions，the d50 of fine powder particle size is 24.90 μm，and the recovery rate is 88.13%. The predicted value is close to the experimental value，and the regression model had good fitting degree and reliability.

In order to fully grasp the production status and process adaptability of a gold ore dressing plant，in view of the problems of low metal recovery rate，difficult recovery of fine gold and uneven equip‐ ment load in the beneficiation process，the whole process investigation and raw ore process mineralogy re‐ search are carried out.The key processes such as crushing and washing screening，grinding and classifica‐ tion，flotation and the metal grade，recovery rate and classification efficiency of products in each stage are systematically analyzed by means of field investigation，production index analysis，ore multi-element and mineral composition test.The results show that the gold and silver in the ore are the main recoverable metals， mainly in the form of inclusions and fine particles，and some gangue minerals have adverse effects on the re‐ covery process.There is room for optimization in many links of the beneficiation process，especially in the re‐ covery and grading control of fine-grained gold. The process flow diagnosis and optimization should be car‐ ried out regularly to improve the metal recovery rate and process stability.

In order to optimize the high pressure roller mill process of large copper concentrators and reduce investment and operating costs，aiming at the selection of different configuration schemes of high‐ pressure roller mill process in the beneficiation process of large copper mines，a comparative study of typical three-stage two-closed-circuit and four-stage two-closed-circuit high pressure roller mill process schemes is carried out in a large copper mine in Pakistan.The research results show that compared with the four-stage two-closed-circuit process，the construction investment of the three-stage two-closed-circuit process is re‐ duced by 69.7619 million yuan，the unit ore operation cost is reduced by 0.79 yuan/t，and the present value of the cost is reduced by 184.4742 million yuan.At the same time，the three-stage two-closed-circuit pro‐ cess has the significant advantages of lower operating cost，higher system adaptability and reliability due to the small number of equipment and small building scale. Under the premise of meeting the requirements of ore treatment，the three-stage two-closed-circuit high pressure roller mill process scheme has better econo‐ my and operability.

The ore properties of a new mining area of a gold mine have changed. Now，the high-sul‐ fur gold mine containing more than 3% sulfur is explored. The gold minerals are mainly embedded in fine particles，which are closely related to pyrite symbiosis and no longer adapt to the original flotation process. In order to improve the indexes of mineral processing technology，the comparative test of mineral process‐ ing indexes of conventional flotation process and regrinding and re-concentration process is carried out. The test results show that the gold concentrate with yield of 7.69%，gold grade of 22.26 g/t and gold recov‐ ery of 82.25% can be obtained by using stage grinding and flotation process，one stage grinding fineness of -0.074 mm 80%，one roughing，two scavenging and one cleaning process，two stage concentrate regrind‐ ing fineness of -0.038 mm 90%，and two cleaning processes. The process meets the requirements of on�site beneficiation indexes.

In order to effectively develop and utilize carbonate-type fluorite ore resources，aiming at the problems of extremely difficult separation of calcite and fluorite，unqualified product index of fluorite concentrate and low recovery rate of fluorite in the separation process of carbonate-type fluorite ore，based on a new project of carbonate-type fluorite concentrator in an alpine region，the mineralogy research，pro‐ cess flow test，product particle size screening and reagent system research of the ore in the mining area are carried out. The results show that the carbonate-type fluorite ore is difficult to be separated. On the one hand，the carbonate-type fluorite ore contains a large amount of calcite，and both calcite and fluorite belong to calcium-containing minerals. The surface physical and chemical properties of the two are extremely simi‐ lar. When coexisting in the solution，there is mutual transformation between minerals；on the other hand，it is due to the presence of a large amount of fine mud（-0.038 mm）.Based on the research results，when de‐ signing the process flow of the mining area，the crushing and grinding adopts three stage one closed-circuit crushing and screening + pre-screening before grinding + ball milling + closed-circuit classification，the pretreatment adopts enhanced slurry adjustment + pulp heating，the selection adopts two roughing + coarse tail desliming + two scavenging + eight cleaning + one cleaning scavenging + coarse concentrate regrinding + fine tail desliming，the collector adopts emulsified oleic acid，and the inhibitor adopts acidified water glass and tannin extract.

In order to improve the ore blending efficiency and resource utilization rate of an open-pit copper-cobalt mine，aiming at the problems of large fluctuation of ore grade，low efficiency of transportation scheduling and unscientific yard management in the existing ore blending process，the investigation and op‐ timization of production ore blending process are carried out.Through data collection and analysis，the key problems such as lack of connection between mining plan and production scheduling，uneven ore mixing and insufficient yard capacity are identified. In view of these problems，optimization measures such as ore classification management，intelligent transportation scheduling，layered stacking and automatic stacking and reclaiming technology are proposed.Through the implementation of ore grade database and intelligent transportation management system，the ore ratio and transportation efficiency are optimized. In terms of yard management，layered stacking and three-dimensional laser scanning technology are used to significantly im‐ prove the mixing uniformity of ore.In terms of mechanical equipment，the stability of equipment operation is improved by increasing maintenance frequency and online fault diagnosis.After the implementation of the op‐ timization scheme，the fluctuation of ore grade is controlled within ±3%，the transportation efficiency is in‐ creased by 25%，the ore accumulation standard deviation in the yard is reduced to 0.06%，and the produc‐ tion efficiency is increased by 12%. The optimized ore blending process effectively improves the recovery rate of mineral processing and the stability of product quality，which provides valuable experience for pro‐ duction and ore blending process optimization in similar mining areas，and has positive demonstration signif‐ icance.

In order to optimize the two-stage grinding process index of Meishan Iron Mine，aiming at the problems of low yield and substandard fineness of easy selecting grade in the grinding products of the two-stage ball mill，the experimental study on the influence of steel ball gradation，medium filling rate and grinding concentration on the grinding effect is carried out.The experimental results show that when the ratio of ϕ60 mm and ϕ40 mm replenish steel balls is 40%:60%，the filling rate is 42%，and the grinding concen‐ tration is 75%，excellent grinding effect can be obtained.Compared with the original scheme on site，the yield and grinding fineness of the easy selecting grade are increased by 16.92 and 10.66 percentage points respectively.Reasonable optimization of steel ball grading，filling rate and grinding concentration can effec‐ tively improve the quality of grinding products，and has important guiding significance for optimizing the grinding process index of the concentrator.

The lead grade of a lead-zinc oxide ore in Yunnan is 1.67%，the zinc grade is 9.21%，and the zinc oxidation rate is 55.81%. In order to improve the recovery rate of lead-zinc oxide ore and avoid the waste of ore resources，aiming at the problems of various elements，high oxidation rate and difficult flotation of lead-zinc oxide ore at the present stage，experimental studies on grinding fineness，reagent system and flotation process are carried out.The test results show that the mixed flotation of zinc sulfide and zinc oxide is beneficial to shorten the flotation process. Under the optimal test conditions，the closed-circuit test obtains lead concentrate with lead grade of 39.25%，zinc content of 13.54%，lead recovery rate of 59.90% and zinc concentrate with zinc grade of 50.24%，lead content of 2.13%，zinc recovery rate of 77.52%. The zinc recov‐ ery rate is improved and satisfactory test indicators are obtained.

In order to improve the development and utilization efficiency of a spodumene mine，aim‐ ing at the problems of complex mineral composition and difficult separation of the spodumene，based on the study of ore properties，a comparative test of flotation process under desliming and non-desliming condi‐ tions is carried out.The results show that under the conditions of grinding fineness of -0.074 mm 70%，dos‐ age of adjusting agent sodium carbonate + sodium hydroxide（1 000+300）g/t，dosage of activator magne‐ sium chloride 150 g/t，dosage of combined collector BK452A+BK452B（1 200+800）g/t，without deslim‐ ing，spodumene concentrate with Li2O grade of 5.71% and Li2O recovery of 85.52% is obtained by closed�circuit test with one roughing，three cleaning and one scavenging process，which provides technical support for the efficient development of this kind of ore.

In order to develop and utilize an iron ore in Anhui Province，the ore property analysis and beneficiation test are carried out on the samples obtained from the exploration.The test results show that un‐ der the conditions of the first grinding fineness of -0.076 mm55%，the amount of xanthate 150 g/t and the amount of 2# oil 36.8 g/t，the iron ore is recovered by the combined process of flotation and magnetic separa‐ tion. The sulfur concentrate with sulfur grade of 37.44% and sulfur recovery of 73.93% is obtained by closed-circuit test of one roughing，two cleaning and one scavenging flotation.Subsequently，the magnetic separation pre-concentration test is carried out on the flotation tailings，and the magnetic field strength is 143.24 kA/m. The next grinding and magnetic separation tests are carried out on the obtained magnetic pre�concentration concentrate. The second-stage grinding fineness is determined to be -0.045 mm88%. The mag‐ netic field strength of one roughing and one cleaning in the second-stage magnetic separation is 143.24 kA/m and 111.41 kA/m，respectively. Finally，an iron concentrate with TFe grade of 64.59% is obtained.The grav‐ ity separation test of high intensity magnetic-spiral chute 1 roughing 1 cleaning is carried out on the low in‐ tensity magnetic comprehensive tailings. The high intensity magnetic field strength is 159.15 kA/m，and the iron concentrate with iron grade of 51.30% is finally obtained. It is combined with the low intensity magnetic concentrate to form a total concentrate. The total iron grade of the total concentrate is 64.06%，the iron re‐ covery rate is 60.64%，and the sulfur grade is 0.031%.

In order to efficiently utilize a Xuanlong-style oolitic hematite，aiming at the problem that iron-containing minerals and gangue minerals are difficult to separate from each other，the process mineral‐ ogy characteristics were analyzed，and the pure mineral wave absorption test and wave absorption character‐ istics of its constituent minerals were analyzed. The experimental results show that the power has an impor‐ tant influence on the absorbing ability of hematite，limonite，siderite，magnetite，apatite and quartz. When the power is lower than 500 W，the power has little effect on the absorbing ability of minerals，and even has no effect on quartz. When the power is more than 500 W，with the increase of power，the heating rate of min‐ erals becomes faster，and the absorbing ability becomes stronger and stronger. The absorbing properties of minerals are related to magnetism. The stronger the magnetism is，the stronger the absorbing ability is. The absorbing ability of hematite，limonite，siderite and apatite is similar，the absorbing ability of magnetite is the strongest，and the absorbing ability of quartz is the weakest.

Due to the change of ore properties，the recovery index of an iron mine in Liaoning fluctu‐ ates greatly，and the tailings run seriously.In order to explore a suitable beneficiation process and reduce the metal loss rate of tailings，systematic experimental studies such as wet pre-concentration，grinding fineness optimization，and magnetic separation field strength exploration are carried out for the iron ore，and appro‐ priate process parameters are determined. The test results show that the concentrate product with yield of 38.47%，iron grade of 63.25% and total iron recovery of 79.09% can be obtained by using the optimized two-stage grinding and four-stage magnetic separation process.The overall separation index is good，which provides scientific basis and technical support for the efficient development and utilization of the iron ore， and is of great significance to improve the utilization rate of iron ore resources.

The lead grade of a lead-zinc oxide ore in Huili，Sichuan is 1.35%，the zinc grade is 7.34%，and the lead oxidation rate is 62.96%.In order to improve the recovery rate of lead and realize the comprehensive utilization of ore resources，aiming at the problems of copper，lead，zinc，sulfur，iron and other elements in the raw ore，the high oxidation rate of lead and zinc，and the difficulty in separating some oxidized ore，on the basis of the study of ore properties，the experimental research on the optimization of separation process and dosage of beneficiation reagents is carried out.The test results show that under the op‐ timum test conditions，the closed-circuit process of 3 cleaning 1 scavenging lead selection，lead selection tailings zinc floatation，zinc 2 cleaning 1 scavenging is adopted to realize the efficient separation of lead ox‐ ide，and the beneficiation index of lead oxide concentrate grade 56.54% and lead recovery rate 59.85% is obtained，which significantly improves the total recovery rate of lead.

In order to use an iron concentrate to process ultra-pure iron concentrate with an iron grade of more than 71%，based on the analysis of mineral properties of ordinary iron concentrate，experimental studies on grinding，magnetic separator separation，elutriator separation and flotation were carried out. The test results show that the ordinary iron concentrate is ground to −0.043 mm 75.56%，and the grinding prod‐ ucts are separated by an elutriation machine with fixed magnetic field of 95.52 kA/m，circulating magnetic field of 83.58 kA/m，compensation magnetic field of 83.58 kA/m，and rising water volume of 1 200 L/h.Un‐ der the conditions of flotation concentration of 40% and cationic collector Gy dosage of（60+30+15）g/t，the ultra-pure iron concentrate with yield of 92.55%，iron grade of 71.35% and iron recovery of 94.10% was fi‐ nally obtained through a closed-circuit reverse flotation test of one roughing and two cleaning. The recom‐ mended process flow for the production of ultra-pure iron concentrate by ordinary iron concentrate is grind‐ ing-elutriation machine magnetic separation-reverse flotation.

In order to determine the suitable beneficiation process flow and reagent system for a high calcium，high silicon and low grade refractory fluorite ore，and obtain satisfactory test indexes，aiming at the characteristics of high CaCO3 mineral content，fine crystal size，coarse crystal size of most fluorite miner‐ als and mutual encapsulation of a small part of fluorite and quartz minerals in the ore，the flotation process exploration，roughing grinding fineness，inhibitor type，regrinding position and grinding fineness conditions are studied. The test results show that the two-stage grinding process of roughing grinding-roughing-two cleaning-concentrate regrinding-five cleaning is adopted. The grinding fineness of roughing is -0.074 mm 60%. The cleaning inhibitor adopts the combination of water glass and DDE. The best regrinding position is after three cleanings，and the regrinding fineness is - 0.038 mm 75%. The fluorite concentrate with CaF2 grade of 97.50% and recovery of 90.08% is obtained in the closed-circuit test.The problem of fluorite and quartz inclusions dissociation and the influence of calcite argillization can be effectively solved by stage grinding and stage separation process. The use of water glass + DDE combined inhibitors can replace tradi‐ tional inhibitors to achieve effective inhibition of calcium carbonate-containing minerals.

Fine-grained tailings have the characteristics of low permeability coefficient，slow consoli‐ dation speed and poor mechanical properties. The construction of high dams is not conducive to the stabili‐ ty of tailings reservoirs. In addition，the influence of complex terrain directly affects the safe operation of fine-grained tailings dams when special conditions such as failure of drainage facilities or increased rain‐ fall occur. Taking a 200 m high tailings dam as an example，the tailings dam in three valleys at the same time，the three-dimensional numerical analysis method is used to carry out the analysis of the interaction law of seepage field and stability and the study of control saturation line. The results show that due to the comprehensive influence of complex topographic conditions such as excessive gully angle，regional seep‐ age and narrow dam axis，the spatial seepage characteristics of high dam are obviously different. The satu‐ ration line in the dam abutment area is 2~3 m higher than that in the surrounding area，which is the most critical area for dam seepage control. When the dam height is 200 m，the depth of the control saturation line is 23 m. The key area of the dam body adopts local horizontal drainage measures to encrypt and control the local infiltration line to ensure the safe operation of the tailings reservoir.

In order to study the problem of retaining water proof coal and rock pillars under the condi‐ tion of gully mining in loess gully area，taking the 200 working face of Shuanglong Coal Mine as an exam‐ ple，according to the structural and hydrogeological characteristics of overlying strata in coal mines，the de‐ velopment height of water-conducting fracture zone and the failure law of overlying strata under mining con‐ ditions are analyzed by engineering geological analogy method and numerical simulation method. The results show that the crack-mining ratio of 200 working face is determined to be 28 by engineering geological analo‐ gy method，and the development height of water-conducting fracture zone is 50.40~89.60 m. By analyzing the range of plastic failure zone and vertical displacement of overlying rock after mining influence，when the working face continues to advance to 500 m，the overlying rock of coal seam roof has been completely de‐ stroyed，and the height range is 51.2~95.8 m. The development height of water-conducting fracture zone is closely related to the buried depth and thickness of coal seam in working face. When the height of waterproof coal pillar in Quaternary aquifer of 200 fully mechanized mining face is 58~110 m，it meets the require‐ ments of ditch mining. The field practice shows that after the mining of the working face，the water of the Wangcungou river is not introduced into the working face，and the safe mining and water-preserved mining are realized. The research results can provide reference for coal mining in loess gully region.

In order to study the mechanism of freeze-thaw damage and failure of granite with fissures， four groups of granite samples with prefabricated fissures inclination angles of 0°，15°，30° and 45° are sub‐ jected to freeze-thaw cycle tests. The strain gauge and thin film sensor are used to measure the frost heaving force and the strain change at the crack tip during the freeze-thaw process，and the frost heaving force，longi‐ tudinal and transverse strain of the rock samples with freeze-thaw cracks are analyzed. The results show that with the increase of freeze-thaw cycles，the longitudinal and transverse strains of fractured rock mass in‐ crease gradually，while the frost heaving force decreases gradually. The larger the inclination angle of the initial prefabricated fissure，the smaller the variation range of the longitudinal and transverse strains of the frozen-thawed rock sample. According to the variation trend of longitudinal and transverse strains and frost heaving force of granite under single freeze-thaw cycle，it can be divided into six stages of inoculation，frost heaving damage，recrystallization，thermal expansion stage，melting reduction and residual deformation. The more the number of freeze-thaw cycles，the more serious the internal damage of the rock sample，resulting in the greater residual strain of the freeze-thaw fissured granite rock.

As a man-made geological disaster，the debris flow in the waste dump is formed by the com‐ bined action of material source，topography and water source conditions. It has the characteristics of strong concealment，easy start-up and high frequency. Through on-site investigation，the dumping materials of a waste dump are mainly waste soil and gravel. The physical and mechanical properties of the loose accumula‐ tion body are poor，and the upper part of the fine particle content is significantly different，showing a natural grading phenomenon. In terms of topography and geomorphology，the quantitative score of the susceptibility of gully debris flow in the waste dump site is 55 points，which is a mild susceptibility level. The overall ter‐ rain is gentle and the loose material reserves are moderate. In terms of water source conditions，the average annual precipitation in the region is 656 mm，concentrated in July-September，and the maximum daily pre‐ cipitation is 109.2 mm. The drainage facilities can resist the once-in-a-century rainstorm. Based on the analysis of the current situation，the possibility of gravity，hydrodynamic and composite debris flow in the waste dump is low. Under extreme conditions ( interception and drainage failure + continuous rainstorm + six-level earthquake )，the dump may be unstable，and the debris flow scale prediction is about 6 000 m3 . The research results provide a theoretical basis for the prevention and control of mine dump disasters.

Taking the gas test roadway in the II84 mining area of Guobei Coal Mine in Huaibei mining area as the engineering background，the deformation evolution law of the surrounding rock during the exca‐ vation disturbance of the main roadway in the strong structural area of the kilometer deep mine is deeply ex‐ plored. The comprehensive control technology method of the stability of the surrounding rock of the kilome‐ ter deep mine roadway is proposed，and the importance of timely support is verified. The results show that the average buried depth of the gas test roadway in II84 mining area is large (1 108 m)，the formation temper‐ ature is high ( 43.35°C~49.84°C )，and it crosses multiple faults，resulting in obvious ground pressure. With the increase of the distance from the excavation face，the growth rate of the roof subsidence of the roadway shows a decreasing trend，and when the distance from the excavation distance is about 2 times the width of the roadway，the growth rate of the roof subsidence gradually tends to be stable. With the increase of the bur‐ ied depth of the roadway，the growth rate of the roof subsidence with the advancing distance of the excava‐ tion face is also increasing，and the plastic zone of the surrounding rock is increased by about 1.5~2.1 times. Under the condition of active and timely support，certain continuous deformation and overall displacement of surrounding rock are allowed to occur，which is conducive to the stability control of surrounding rock in kilometer deep mine. The research results provide a reference for the stability control of surrounding rock in the process of excavation disturbance in kilometer deep mine roadway.

In order to make full use of the mineral resources of Mirador North Mine，reduce the amount of rock stripping，improve the utilization rate of resources and the economic benefits of the mine， the NPV optimization program is used to optimize the open-pit mining boundary of Mirador North Mine. Based on the technical and economic parameters，the final slope angle and other main parameters of Mira‐ dor South Mine，the main parameters of Mirador North Mine boundary optimization are determined. Ac‐ cording to the constructed model，a total of 41 boundaries are delineated，and the incremental value and cumulative value of the NPV open-pit optimization boundary are obtained，and the change trend is ana‐ lyzed. The results show that after the Pit31 boundary，the net present value increment becomes negative， the cumulative value of the net present value is the largest，and the Pit31 boundary is the optimal reference boundary. The amount of ore in the boundary is not sensitive to the rise of metal price，but very sensitive to the decline of metal price. The maximum elevation of the optimized boundary stope is 1 135 m，the elevation of the closed ring is 900 m，the bottom elevation of the open-pit mine is 510 m，the mining depth is 390 m，and the mining height is 235 m. The amount of ore in the boundary increased by 59.286 million tons， with an increase of 2%，and the average grade of the increased ore is 0.385%，which extend the service life of the mine and ensure the full development and utilization of mineral resources.

Taking Shigetai Coal Mine in Shendong mining area as the research object，the numerical simulation，mine pressure measurement and similar simulation test methods are comprehensively used to compare and analyze the stress distribution and movement evolution law of overlying rock under the condi‐ tions of single coal seam mining and repeated mining，and the influence mechanism of repeated mining on overlying rock movement in shallow buried close distance coal seams is discussed. The results show that compared with single coal seam mining，the stress concentration degree of overburden support is reduced during repeated mining，but the high support stress area is formed near the stop line of upper coal seam， which is easy to induce support crushing accident. With the advancement of lower coal seam mining，the in‐ terlayer overlying rock is broken，and the overlying rock subsidence shows the dynamic characteristics of 'sudden increase-slowing down'，and the influence range of subsidence continues to expand. Repeated min‐ ing promotes the evolution of overburden structure to a single caving zone，which aggravates the risk of roof instability in the working face. The research results can provide a theoretical basis for safe and efficient min‐ ing of shallow buried close distance coal seams.

The characteristics of geothermal gradient changes are influenced by multiple factors such as geological structure，stratigraphic lithology，hydrogeological conditions，cap rock thickness，and deep active fractures. This article uses the actual temperature measurement data of drilling wells in Jinchanghe mining area，Baoshan City，to draw isotherm maps from two scales of drilling depth and elevation. At the same time，combined with regional structure and rock mass distribution，the distribution laws of ground tem‐ perature at different depths and elevations are compared，and the characteristics and main controlling fac‐ tors of ground temperature gradient changes are comprehensively analyzed and studied. The differences in geothermal geological conditions，genesis，and structural thermal evolution in the region are summarized. The research results indicate that at the same elevation，there is a significant concentration of thermal ef‐ fects around the F2 and F10 fracture zones. The temperature increase of the F2 fracture is slightly higher than that of the F10 fracture，and as it moves westward，the ground temperature increases with depth，while a rela‐ tively low temperature section appears clearly in the exposed rock mass area. Under the same depth condi‐ tions，comparing the geothermal maps of different depths，there are two obvious differences. Firstly，there is a difference in geothermal temperature near the fracture zone. On the F2 and F10 fracture zones，the tempera‐ ture is slightly higher. Secondly，near the rock mass，a slightly lower circle is clearly present. Through com‐ prehensive research，it has been determined that the thermal anomalies in the region are mainly controlled by intrusive rock activity and fault activity. The shallow sedimentary rocks are continuous and intact，form‐ ing a good thermal insulation cover layer.

The deep cone thickener plays an important role in the field of mine tailings treatment and resource recovery，but the change of tailings particle size has a significant effect on its operation perfor‐ mance. Taking Baoshan Mine in Hunan Province as the research object，the whole tailings were mixed in different proportions，and the particle size distribution，rheology and dynamic flocculation sedimentation tests were carried out，and the numerical simulation was carried out. The test results show that the particle size composition，rheological parameters and sedimentation performance of different graded tailings are ob‐ viously different，and the particle size of tailings affects the sedimentation speed and concentration effect. Based on the paste filling theory，in order to deal with the change of tailings particle size，the countermea‐ sures of optimizing process parameters（adjusting feeding speed，flocculant addition amount and rake frame speed）and tailings pretreatment（classification and grinding）are put forward to improve the opera‐ tion efficiency of deep cone thickener and provide technical support for the sustainable development of min‐ ing enterprises.

The phosphorus in the overflow of an inclined plate thickener for iron tailings in Chengde has not been effectively recovered due to fine particle size and large mud content，which not only wastes resources，but also affects the efficiency of enterprises. In order to solve this problem，an experimental study on the adaptability of the cyclone static microbubble flotation column to the phosphorus separation of an inclined plate overflow in Chengde was carried out，and the economic estimate was carried out on this basis. The test results show that the average feed concentration of cyclone（inclined plate overflow）is 6.17%，and the grade of P2O5 is 2.0%. The sand concentration is 33.15%，the yield is 45.66%，the P2O5 grade is 3.5%，and the P2O5 recovery rate is 79.19%. The average feed (cyclone grit) P2O5 grade of the cy‐ clone static microbubble flotation column is 3.5%，the concentrate P2O5 grade is 29.6%，the tailings P2O5 grade is 0.5%，and the concentrate P2O5 recovery rate is 86.47%.In the preliminary industrial design， two-stage cyclones were selected for thickening and desliming，with two sets of FX100-PU-BL ×42 cy‐ clones and one set of FX100-PU-BL×16 cyclones. The flotation equipment of one roughing，two cleaning and one scavenging is one FCSMC-3 000×8 000 flotation column（roughing），one FCSMC-2 400×7 000 flotation column（cleaning 1），one FCSMC-2 000×7 000 flotation column（cleaning 2），and one FC‐ SMC-2 800×7 000 flotation column（scavenging）. The economic budget estimates show that the total in‐ vestment is 8.975 million yuan，and the annual production efficiency is 3.937 8 million yuan. It is proved that the cyclone static microbubble flotation column has good adaptability to the overflow phosphorus sepa‐ ration of inclined plate thickener in Chengde area，which can provide reference for the transformation of concentrator.

In order to meet the high strength requirements of ferrite products in the field of electronic components，and solve the problem that the current products are prone to cracks and crushing in practical applications，the key factors affecting the strength of ferrite products are analyzed in depth，and an effective promotion strategy is proposed.Through the systematic investigation of raw material purity，particle size dis‐ tribution，chemical ratio，preparation process parameters，and microstructure (grain size，grain boundary state，porosity)，the microscopic mechanism of the influence of various factors on product strength is re‐ vealed.The results show that the density and uniformity of the sintered body can be significantly improved by selecting the main and auxiliary raw materials with high purity and uniform particle size and optimizing the proportion of each component in the formula.At the same time，precise control of molding process parame‐ ters and precise regulation of multi-stage sintering temperature and atmosphere can effectively improve grain growth and grain boundary binding force，and reduce porosity. It can provide theoretical guidance and practical basis for the development and production of high-performance and high-reliability ferrite materi‐ als. It can effectively reduce the defective rate of products，improve the overall reliability and service life of electronic equipment，and then improve customer satisfaction.

With the continuous enrichment of market application scenarios，the types of permanent magnet magnetic separators are also increasingly diversified，and the structural characteristics of each mag‐ netic separator are different. In order to deeply study the differential performance of these diversified perma‐ nent magnet magnetic separators in dealing with material characteristics and adapting to the environment， starting from the core link of magnetic system structure design and assembly process of permanent magnet magnetic separators，combined with magnetic circuit analysis，material selection and separation dynamics theory，the structural design principle and assembly process technology of the magnetic system of the core components of the three mainstream permanent magnet magnetic separators of drum type，roller type and plate type are discussed in depth. Through comparative analysis，it is found that permanent magnet magnetic separators with different magnetic field characteristics have unique advantages in magnetic field strength， separation efficiency and applicable scenarios，in order to provide theoretical basis and technical reference for the optimization and engineering application of mineral separation equipment，and promote the further development of permanent magnet magnetic separation technology.

In order to carry out ecological restoration and treatment of abandoned mines，from the perspective of comprehensive utilization of industrial solid waste，it is proposed to use industrial solid waste for ecological backfill of abandoned mines. Taking the treatment of an abandoned mine in Huoqiu County，Anhui Province as an example，based on the principle of combining comprehensive utilization of solid waste with mine restoration and treatment，the ecological backfilling process of abandoned mines， backfilling and pollution control requirements，current situation investigation of abandoned mines，proper‐ ty investigation of solid waste，and backfilling project of abandoned mines were analyzed，and the ecologi‐ cal backfilling way of abandoned mines was determined. The analysis and research show that the tailings in Huoqiu County can be ecologically backfilled to realize the effective utilization of the abandoned mine vol‐ ume of about 49.362 m2 . After ecological backfill，it can be reclaimed into forest land，which can realize the reuse of land resources.

Aiming at the problem of coal spontaneous combustion caused by air leakage in goaf of 2-1 coal seam working face in Menkeqing Coal Mine，through the combination of experiment and numerical sim‐ ulation，the variation law of low temperature oxidation characteristic temperature of coal body under differ‐ ent air leakage conditions and its correlation with oxygen concentration are studied. The simultaneous ther‐ mal analysis test of controlling carrier gas flow and oxygen concentration is used to simulate the conditions of oxygen supply and heat storage in goaf，and the influence of different air leakage intensity on the tempera‐ ture field and flow field in goaf is analyzed based on numerical simulation. The results show that the air leak‐ age intensity has little effect on the thermogravimetric curve of coal，but under the same oxygen concentra‐ tion，the heat dissipation effect of larger airflow will significantly delay the low temperature oxidation pro‐ cess of coal. The linear correlation between characteristic temperatures T1 and T2 and oxygen concentration is weak，while T3 and T4 decrease with the increase of oxygen concentration in a quadratic function. The nu‐ merical simulation shows that the high temperature area of the residual coal seam is mainly concentrated near the return air roadway，which is distributed in a triangular shape near the wall surface，and the in‐ crease of ventilation volume will lead to the migration of the velocity field and temperature field in the goaf to the deep. According to the research results，the fire prevention technology of gas monitoring strategy optimi‐ zation，air leakage prevention method innovation and the fire extinguishing method of injecting slurry，inert gas and gel foam material are put forward，which has important guiding significance for ensuring the safe mining of coal mines.

In order to solve the support problem of the mining roadway in Huayang No.1 Mine under the mining disturbance of the adjacent working face，taking the return air roadway support of the 151306 working face of the mine as the engineering background，the monitoring method of surrounding rock fracture is used to grasp the deformation and instability characteristics of the surrounding rock，and the reasons for the instability of the surrounding rock are analyzed. The repair and reinforcement scheme is proposed and verified by industrial tests. The results of mine pressure monitoring show that under the influence of mining near 151304 working face，the surrounding rock of 151306 return airway under the original anchor net cable support condition has serious convergence deformation and large range of loose failure. The depth of loose failure of roof strata is 2.8~3.5 m，and the depth of loose fracture of solid coal side is 3.0~3.5 m，which can not guarantee the stability of surrounding rock of roadway. The special-shaped anchor cable with umbrella�shaped reed device is designed for secondary reinforcement. The tension test in 151306 return air trough shows that the special-shaped anchor cable can provide stable anchoring force ( ≥ 200 kN ) under the condi‐ tion of broken surrounding rock，which can effectively solve the anchoring problem of traditional anchor ca‐ ble in weak surrounding rock. The detailed reinforcement support scheme of 151306 return air crossheading is designed，and the original bolt and anchor cable are re-prestressed or tensioned. The surrounding rock de‐ formation data show that the deformation rate and deformation of surrounding rock after repair and reinforce‐ ment are significantly lower than those under the original support conditions. Compared with the original sup‐port，the convergence of the two sides is reduced by 77.8 %，and the convergence of the roof and floor is re‐ duced by 69.2 %，which achieves better surrounding rock control effect.

In order to accurately predict the risk level of coal spontaneous combustion，aiming at the limitation of low prediction accuracy of traditional BP neural network model，a prediction model of coal spontaneous combustion risk level coupled with improved grey wolf optimization algorithm（IGWO）and tra‐ ditional BP neural network is proposed.Firstly，a new random dynamic control factor is proposed by using Tent mapping and Levy flight，which improves the development ability and convergence speed of grey wolf optimization algorithm（GWO）.Then，the effectiveness of the IGWO algorithm is verified by six standard test functions.Finally，taking 50 sets of sample data in the goaf as the research object，the IGWO-BP predic‐ tion model of coal spontaneous combustion risk level is established.The absolute value of relative error is used as the evaluation index of model prediction accuracy，and the prediction results of GWO-BP and BP models are compared and analyzed.The results show that the IGWO algorithm has better convergence speed and prediction accuracy than the traditional grey wolf optimization algorithm（GWO）.The prediction effect of IGWO-BP model is better than that of GWO-BP and BP models，and the absolute value of relative error is less than 8%，which greatly improves the prediction accuracy.This research can provide important decision support for the monitoring and early warning of coal mine spontaneous combustion fire.

Aiming at the problem of rock mass quality evaluation of underground mining engineering， taking the rock mass of the 3 000 m level middle section of Zaozigou Gold Mine as the research background， the entropy weight method is used to determine the weight of the evaluation index，and a five-element set pair analysis model based on the entropy weight method is constructed. Five indexes of rock uniaxial com‐ pressive strength，RQD index，joint spacing，joint state and groundwater condition are selected to evaluate the quality of surrounding rock. The results show that the diorite porphyrite in roadway is hard-hard intru‐ sive rock，and the quality grade of surrounding rock in its distribution section is Grade II. The slate belongs to hard-weak metamorphic rock，and the quality grade of its distribution section is relatively low，mostly Grade III. The evaluation results of the set pair analysis method are in good agreement with the RMR classi‐ fication results，and can intuitively reflect the degree of closeness between the evaluation rock mass and each grade standard. It is proved that the method is reasonable and feasible for the rock mass quality evalua‐ tion of underground mining engineering.

In order to study the feasibility of underground sludge recovery in skarn mines，taking a skarn iron mine as the research background，a series of sludge recovery research and practice are carried out in view of the problems of more sludge，long cleaning time，difficult treatment and high cost in this type of underground mines.Through the sampling of sludge in the drainage ditch，sedimentation tank and sump of each production section，the grade test is carried out. It is concluded that the average grade of sludge iron content is 22.41 % ，which is greater than the boundary grade and had recovery value. By analyzing the causes of underground sludge，formulating sludge recovery plan and carrying out sludge recovery practice， not only the iron ore resources in the sludge are extracted，but also the service life of the underground drain‐ age pump is improved，and the metal recovery rate is improved and the ore loss rate is reduced. It is further proved that the sludge of the skarn type mine has good utilization value，and provides a feasible reference ex‐ ample for similar mines in underground sludge recovery.

The Dexing Copper Mine employs FFP1516 40/40 M50 diaphragm filter presses for concen‐ trate filtration. Due to the properties of the slurry，scaling on the filter plates is challenging to remove，se‐ verely affecting filtration efficiency. Improper cleaning methods can even shorten the service life of the filter plates. To address these issues，systematic experimental research and production practices were conducted. Based on the experimental results，the primary component of the scale is calcium hydroxide，along with mi‐ nor amounts of calcium sulfate dihydrate，copper iron sulfide，iron disulfide，and flotation reagents.Compar‐ ative studies on chemical cleaning agents，including industrial hydrochloric acid，slurry cleaning agent KJ- 26，sulfuric acid and ammonia solutions，reveal that KJ-26 achieves effective descaling while being safe and environmentally friendly. Physical removal methods for internal filtrate channel deposits，consisting of hard springs，high-pressure hoses and "soft drill bits" demonstrate that the "soft drill bit" is safe，reliable and highly efficient.By combining chemical immersion with KJ-26 and physical cleaning using the "soft drill bit"，the moisture content of the filter cakes during their lifecycle decreased from 10.8% to 9.9%，reducing transport costs and concentrate leakage. Additionally，the service life of filter plates extended from the de‐ signed 3 years to 4.5 years. This proper cleaning and repair method can save approximately 33，000 RMB per filter plate of operational costs.

To address the decline in production capacity and economic efficiency，and to ensure sta‐ ble output and financial performance，a mining company purchases non-mainstream ores to carry out pro‐ cessing business. Taking Dongshan Concentrator as a case study，it analyzes how fluctuations in raw materi‐ al prices，processing costs，and the mix ratio between self-mined and processed ores affect economic re‐ turns，and establishes a dynamic economic evaluation model. The research highlights the importance of ore blending in the concentrator’s production process and points out that the current cost allocation method fails to accurately reflect actual resource consumption and synergistic benefits. To tackle these issues，the study proposes building a market price analysis model to manage risks，optimizing ore-blending ratios，and inno‐ vating business models. It applies a break-even analysis model to guide operational decisions，adopts a vari‐ able cost separation method to improve cost accounting，derives the optimal mixing formula for self-mined and purchased ores，and promotes a "trade + base" toll-processing model. Under this model，professional trading companies handle procurement，sales，and risk management，while mines focus on production and earn processing fees. Research findings show that implementing these strategies not only generates direct economic benefits but also significantly improves the output and recovery rate of self-mined ores，thereby enhancing overall production efficiency. This systematic approach offers an effective solution for resource�declining mining enterprises seeking to improve economic performance.

In order to optimize the stope structure parameters of stage chamber mining method in a calcite mine and ensure safe and efficient mining，theoretical analysis and numerical simulation methods are comprehensively used. Firstly，the stability of the stope roof is theoretically calculated based on the load transfer intersection line method，the Platts arch method and the thickness-span ratio method.At the same time，combined with the theoretical formula of pillar strength and the safety factor method，the overall sta‐ bility of the pillar in the designed mining depth is evaluated. The theoretical analysis results show that the original 14 m stope span is not enough to ensure the safety and stability of the roof and pillar system，and there is a mining risk. In order to ensure the safe mining of the ore body，the stope span should be opti‐ mized to 9 m. Furthermore，FLAC3D numerical simulation software is used to verify the theoretical analysis results. The simulation results are consistent with the theoretical prediction. It is confirmed that the struc‐ tural parameters under 9 m span can effectively maintain the stability of the stope，and the optimization of the design parameters of the original stage room method is realized，which provides a technical basis for the safe mining of this kind of mine.