Yandan-Yantang gold deposit is located in Leye County，Guangxi，which is a large-scale carlin-type gold deposit，with a gold resource of more than 20 tons，newly discovered in Yunnan-Guizhou-Guangxi “Golden Triangle” area，China.The deposit is located in the northwest of Lingyun-Leye isolated carbonate platform，Guangxi.The host rock is calcareous sandstone with mudstone of Baifeng Formation of Middle Triassic.The orebodies are mainly controlled by anticlines and faults.The orebodies mainly occurs as vein type one in fault fracture zone，and a small amount are stratabound orebodies.The largest orebody is located in the core of the anticline and controlled by F1 fault，inclining northward，with a dip angle of 30°~60°，a width of 1.0~38.8 m，a length of nearly 2.5 km，a depth of 50~400 m，and Au grade of 0.50×10-6~7.00×10-6 in general，and the average grade is 2.0×10-6.The main mineralization and alteration are silicification，kaolinization，pyritization，arsenopyrite mineralization and stibium mineralization.The gold bearing minerals are arsenian pyrites and arsenopyrites.It has a typical combination of low temperature elements such as Au-As-Sb-Hg.Generally，it has typical carlin-type gold deposit characteristics.The results of soil and rock geochemical survey show that the Au and As elements in the ore-bearing fracture zone have good coincidence，they are all located in the core of anticline and distributed along the striking of F1 fault.However，only As anomaly appears in the east of the fault，which is consistent with the feature that As is the front halo of orebody in carlin-type gold deposit，suggesting that the orebody may lie to the east.The geophysical data of TDIP and CSAMT show that the gold orebody has the characteristics of low resistivity and high intensification rate.The high intensification anomaly of TDIP lies to the east，which also shows that the gold orebody tends to extend to the east.Based on the geological characteristics and geophysical and geochemical anomalies，it is considered that the F1 reverse fault in the core of anticline is the main ore-controlling fault，and the orebody has the trend of lying to the east，suggesting that the deep part of the mining area has good ore prospecting potential.
Jiaodong gold province is one of the major gold producing areas in China.Linglong gold orefield is located in the northwestern Jiaodong，which is a typical representative of the super large quartz-vein type gold orefields.In recent years，many scholars have carried out detailed geological prospecting and genesis of the Linglong gold orefield，but there are still controversies about the sources of ore-forming materials and fluids，and the mechanism of gold mineralization.Besides，deep exploration of gold ore is urgently needed to be solved.In this study，the Jiuqu gold deposit，located in the eastern part of the Linglong gold orefield，were sampled.The study of pyrite，the main gold-bearing mineral in the Jiuqu gold deposit，is of great significance to the genesis and prospecting prediction of the deposit. The mineral graphical and micro-geochemical characteristics of pyrite in different metallogenic stages were studied in detail，such as pyrite-quartz stage，quartz-pyrite stage，quartz polymetallic sulfide stage and carbonate stage.Mineralogy studies have found that there are three main types of native gold associated with pyrite in the Jiuqu gold deposit，mainly including intergranular gold and inclusion gold，with locally appearing of a large amount of fissure gold.The pentagonal dodecahedron of pyrite and its complex aggregates are usually related to the sulfur-rich concentration of ore-forming fluids，which is one of the good signs of gold mineralization.The crushing degree and particle size of pyrite are closely related to the content of primary gold，implying that pyrites with higher crushing degree and smaller particle size have a larger specific surface area，which is conducive to the adsorption of gold.Light-yellow，dark-yellow or yellow pyrite usually contain higher gold contents，while light-yellow white pyrite has a relatively low gold content.The micro-geochemical characteristics of pyrite show that the major elements of pyrite are characterized by iron-rich and sulfur-poor，and that the sulphur fugacity of the ore-bearing fluid gradually decreases during the ascending process.The difference in the chemical structure of pyrite indicates that it has experienced a lot of brittleness and plastic microstructural deformation.Moreover，the temperature of ore-forming hydrothermal fluids from the early stage to the main ore-forming stage generally tends to decrease.According to the mineralogy and mineral geochemical characteristics of the gold-bearing pyrite in the Jiuqu gold deposit，pyrite has a certain indication of ore-forming significance.Pyrite with complex shape，color change，brittleness and plastic deformation charac-teristics of pyrite can be used as prospecting indicators.
In order to mine strip cluster veins efficiently and safely，based on the concept of collaborative mining，the concept of cluster continuous mining and the continuous horizontal layered filling continuous mining method were proposed.First and foremost，the theoretical calculation methods of slab beam，Platts pressure arch method，thick-span ratio method，load transfer intersection line method and structural mechanics beam theory method were used，and the safety factor was introduced to calculate the roof span under different safety factors.The roof safety problem of the continuous mining method is studied.Furthermore，through the analysis，the safe stoping span of cluster continuous mining method is ranged from 23.0 m to 18.6 m. When the safety factor was 2.0，the number of roof span was modeled by ANSYS and verified by Flac3D. For one thing，the numerical simulation results show that the maximum principal stress is 2.84 MPa，and the maximum displacement is 9.7 mm.There is only a small shear stress failure in the middle chamber.For another，the engineering example shows that: when the stope span is 18 m （rounding 18.6 m），there is rock block falling in a small local area of the roof，and the ratio of the length of the falling block to the roof span is 1.67%.The numerical simulation and engineering example results are alike.Finally，the concept of collaborative mining has strong coupling and inclusiveness.Besides，the new concept plays a guiding role for mining complex ore bodies in China，which can better meet the mining requirements.
The regional time-space mining sequence is one of the important strategic methods for underground pressure management at depths and destress mechanical effect is closely related to the time-space mining sequence itself. Aiming at the large-area mining mechanical model of three-dimensional mining sequence from the centre to the periphery at depths， based on the stress transfer process and characteristics of rockburst stress hazard， the stress evolution laws and changes of rockburst stress hazard were studied during the mining process from a single stop to multiple stopes.The research results show that the three-dimensional mining sequence from the center to the periphery at depths can gradually realize the gradual transfer of high stress and the gradual transition of stress hazard around the mining operation area.The destress effect of ground pressure control for the time-space mining sequence at depths is to achieve the desired destress environment reconstruction and the progressive transfer of the stress hazard through the reasonable setting of the three-dimensional mining sequence.The mutual feedback analysis technology based on the combination of numerical simulation and microseismic monitoring could realize high integration of large area numerical simulation and big data of microseismic monitoring， real-time dynamic analysis and tracking evaluation， and it is an effective method to evaluate the destress effect of ground pressure control for the time-space mining sequence at depths.The essence of the destress effect of ground pressure control for the time-space mining sequence at depths is the idea to actively create low stress destress zone in the high-stress environment.This idea had been applied at Nickel Rim South mine in Canada， which had achieved a good destress effect and realized reasonable management for ground control. It is believed that this idea has important guiding significance for deep and ultra-deep mining in China.
The ore body in the No.2 mining area of Jinchuan mine is exploited at the same time in the middle section of +1 000 m and +850 m.With the continuous development of mining，some technical problems in the recovery stage of the horizontal pillar in the middle section of +1 000 m are also highlighted.In the face of more and more serious actual situation，it is necessary to study the stability of horizontal pillar and filling body thoroughly.A detailed field investigation was conducted on the mining environment of the horizontal pillar in the middle section of +1 000 m.On this basis，using the ANSYS and FLAC3D numerical simulation software，the trend analysis of the stress and displacement of the filling body and the ground surface during the recovery of the horizontal ore pillar in the two mining area was analyzed，and the underground filling in the two mine area was revealed.The dynamic pressure distribution law of the body and the ground surface during the whole mining process，the stability of the filling body during the mining of the +1 000 m level pillar in the No.2 mining area was synthetically evaluated，and the stability of the 700 m and +850 m middle section mining was predicted by this method.The following conclusions are mainly obtained：During the mining process，the stress appears obviously，the accumulative displacement of the upper and lower plates is larger.When the thickness of the horizontal pillar is 20~30 m，the stress changes in the pillar，the maximum principal stress reaches the peak，the plastic failure area is in the middle of the rich ore body and has the through phenomenon，and the plastic failure of the pillar is all when the thickness of the horizontal pillar is 20 m.The filling body begins to destroy from the part of the contact zone of the surrounding rock and develops to the center of the filling body，and the filling body on the upper plate is seriously damaged than the filling body on the foot wall.According to the mining practice in the middle section of +1 000 m in the two mining area，two kinds of mining schemes are put forward and compared.The results show that during the mining process，the stress appears obviously，the accumulative displacement of the upper and lower plates is larger，and the two schemes have not appeared the phenomenon of large area collapse.Compared to the comprehensive stress，displacement and plastic failure area，the scheme two is better than the scheme one，but the two schemes are faced with the danger of large area plastic failure and local instability of the horizontal pillar at the end of the pillar mining.
Weak structural plane is an important factor of slope instability in open-pit mines.It is very important to detect the position of weak structural plane accurately and carry out prediction and early warning in time for the production of open-pit mines.The existence of broken rock，mud or groundwater in the fault of mine slope is the main reason for the formation of weak structural plane，which is obviously different from the complete rock mass in terms of physical properties such as apparent resistivity and dielectric constant.In order to find out the influence of engineering geological conditions and meteorological and hydrological conditions on the formation of the weak structural surface，locate the position of the weak structural surface accurately，and analyze the role of the weak structural surface in the process of slope instability，the detection and research on the influencing factors of the slope instability of the open pit mine were carried out with the Bayan Obo iron mine slope as the research object.Because of the factors such as the high and steep slope formed by mining and the deformed slope body，it is difficult to arrange the high-density electrical method on site.The comprehensive geophysical exploration technology of high-density electrical method and ground penetrating radar(GPR) method were used to survey the slope in the study area，and the survey results were explained.Three high-density survey lines，eight high-density electrical sections and two geological radar survey lines were arranged outside the boundary line of the northern boundary of the study area.The results of high-density electrical method show that the apparent resistivity of intact dolomite and slate in the study area is high，while that of broken slate，fault and water bearing slate is obviously decreased.According to the results of GPR，the whole rock mass has strong reflected energy，and the broken slate and fault are reflected shadow area.The comprehensive geophysical exploration method starts from the different physical properties of the slope rock mass to detect the geological structure of the slope.In this study，the high-density electrical method and the ground penetrating radar survey method make use of the development degree of the slope cracks，the difference of the physical properties and the resistivity of the surrounding rock to carry out the fracture distribution survey.At the same time，using the characteristics of good water conductivity and strong electromagnetic wave absorption to carry out the underground water survey，and verify the inversion results with each other，and combine the drilling data and the engineering hydrogeological data to carry out the slope survey in the study area.It can effectively improve the positioning accuracy of the weak surface.
The stability analysis of surrounding rock of underground engineering is related to the safety of underground engineering.The stability of surrounding rock directly determines the success or failure of the underground engineering.Therefore，it is of great significance to carry out the stability evaluation of surrounding rock of underground engineering.Based on cloud theory，the rock uniaxial saturation compressive strength，integrity coefficient，basic rock quality index，groundwater impact correction coefficient，and weak structure surface condition impact coefficient were selected as the surrounding rock stability classification indicators.The combination weight of the above index system was obtained by using DEMATEL decision-making model and entropy weight method，and then 20 sets of measured data of highway tunnel engineering were selected as learning samples to establish a comprehensive decision cloud model for surrounding rock stability classification.It is applied to an example of surrounding rock stability classification for 5 groups of Xiaohongshilazi jade mine.The results show that the discrimination result of the comprehensive decision cloud model is consistent with the actual situation，and the discrimination accuracy can reach 80%，which is better than the discrimination results of the K-nearest neighbor algorithm and the random forest algorithm，indicating that the comprehensive decision cloud model established in this paper has certain application value in engineering practice and can provide a new idea for stability classification of surrounding rocks.
The equity structure is the foundation of corporate governance.It is of great practical significance to establish a reasonable equity structure to improve the corporate governance efficiency.Most literatures use linear regression model or multiple nonlinear model to study the relationship between corporate governance efficiency and equity structure.Few scholars consider the impact of equity concentration on corporate governance efficiency from the perspective of China’s private mining companies，and few scholars consider that there may be a structural mutation between equity concentration and corporate governance efficiency，namely threshold effect.Based on the data of 48 private mining companies listed in Shanghai and Shenzhen from 2013 to 2017，this paper constructs a DEA model to measure the efficiency of corporate governance，and uses a threshold model to explore what kind of equity concentration is more suitable for the current economic environment of China and more effective to improve the efficiency of corporate governance of private mining companies in China.Based on the theory of production function，this paper selects total assets，asset liability ratio and number of senior executives as input indexes，growth and profit rate as output indexes，and constructs DEA measurement model of corporate governance efficiency.The results show that：The total average governance efficiency of China’s private mining companies in 2013~2017 is 0.7092，and the governance efficiency is still low；Only four companies have maintained relatively effective governance，accounting for 8.33% of the total sample；Only 10 companies have five-year average governance efficiency of more than 0.9，accounting for 20.83% of the total sample；There are significant differences in different corporate governance efficiency，and the phenomenon of two-level differentiation is serious.Taking corporate governance efficiency as explanatory variable， Tobin’Q value and corporate age as control variable， equity concentration as explanatory variable and threshold variable， a threshold model of the impact of equity concentration on corporate governance efficiency was constructed， and a multiple regression model of the impact of corporate governance efficiency was constructed with company size as explanatory variable.The results show that：（1）There is a threshold effect and an inverted “U” relationship between the equity concentration and the corporate governance efficiency.When the equity concentration is lower than the threshold of 29.73%，they are positively correlated；When the equity concentration is higher than the threshold of 29.73%，they are negatively correlated.（2） The optimal Largest shareholder holding ratio of private mining companies in China is[0.1873，0.3360].（3） The company size is negatively correlated with the corporate governance efficiency of private mining companies in China.
As a kind of non renewable strategic resource，rare earth is the key strategic basic material for the transformation of traditional industries and the development of emerging industries，which has an important strategic value for China and the world’s high-tech industries.Under the background of the current domestic and international situation，China’s policy adjustment on rare earth export tends to raise international objections.In order to safeguard national interests，meet public demands and eliminate international objections，this paper analyzed the export control of rare earth by using the theory and method of control economics.First of all，on the basis of combing the evolution of China’s rare earth export control and reviewing the current rare earth export control policy system，we divided the evolution of China’s rare earth export control into three stages：Laissez faire stage，strict control stage and comprehensive control stage.Then，taking “public interest” as the core，we constructed the regulatory economic adaptability analysis framework of rare earth export from three dimensions of “externality” control，“departmental interest” control and “incentive” control，and discuss the adaptability with the current international trade rules.Finally，on the basis of this framework，we put forward the basic ideas of establishing and improving the rare earth export control system in China from four levels of demand level，guidance level，utility level and implementation level.The research shows that：The purpose of China’s rare earth export control is to ensure national security，social public interest and sustainable development of rare earth industry；The main body is a diversified control subject with government control as the core；The object is the individual，enterprise and industrial chain related to rare earth industry；The hand is the combination of economic control and social control with relevant laws as the core.Through the establishment of rare earth export control system，we can find the control path that can coordinate the conflict of interest between rare earth export and different stakeholders，and provide reference for the high-quality development of China’s rare earth industry and the development of the world’s rare earth industry.
As the mining depth increases，the ground stress gradually increases，and rock burst phenomenon is likely to occur，which brings great damage to underground roadways and stope.Accurate ground stress magnitude and direction has good reference guidance value to underground engineering and can effectively avoid the occurrence of damage such as rock burst.In order to obtain the accurate ground stress distribution in the deep mining area of Xincheng gold mine，the stress relief method and acoustic emission method were used to measure the in-situ stress of the -830~-1 150 m deep mining area.The specific method of geostress measurement and the solution process of geostress measurement results were expounded.Subsequently，six measurement points of -830 m，-930 m and -1 030 m were measured using the stress relaxation method，and three measuring points in the three levels of -950 m，-1 050 m and -1 150 m were measured by AE method.Among them，the directional disturbance least squares multiple regression was used to improve the accuracy of the six stress components of the hole stress relief method，and the coordinates of the strain gauge were transformed into a space rectangular coordinate system by using the space coordinate transformation formula.The magnitude and direction of the ground stress were calculated by using the LUT-str three-dimensional geostress calculation program.The distribution law of the deep ground stress in the mining area under two different measurement modes was obtained，and the comparative analysis of the measurement results of the two methods were carried out.The results of the two measurement methods show that the horizontal principal stress and the vertical principal stress measured by the two measurement methods both increase linearly，the vertical principal stress is both close to the self-heavy stress of the overburden layer，and the deep stress of the Xincheng gold deposit is horizontal stress mainly，the maximum horizontal principal stress is NWW-SEE direction.The maximum horizontal principal stress measured by AE method is about 1.39 times of self-weight stress，and the stress relieving method is about 1.49 times.The maximum horizontal principal stress.vertical principal stress and horizontal minimum principal stress measured at -1 030 m level with errors of 12.1%，5.35%，and 13.46%，respectively，which have good consistency and provide good support for the exploitation and support design of deep mining areas.
In underground engineering，rock （body） is damaged or destroyed by impact drilling，blasting，crushing and other dynamic disturbance.In this process，external energy conversion and internal energy consumption are inevitable.Energy dissipation is an important factor that causes rock damage and failure state，so it is of great significance to study the dynamic mechanical properties and failure behavior of rock from the perspective of energy. At present，in the research of rock dynamic characteristics，the commonly used equipment are drop hammer，split Hopkinson pressure bar （SHPB） and light gas gun，among which the SHPB test system is generally used to study the dynamic characteristics of rock under medium and high strain rate（10~103 s-1）.In order to quantitatively describe the energy dissipation capacity of rock in the process of dynamic compression，the uniaxial dynamic compression tests of cylindrical red sandstone specimens were carried out with SHPB device，and the failure process of the specimen was recorded by a high-speed camera.The test results show that with the increase of incident energy，the specimen shows three different states：intact，ruptured and broken after the dynamic impact loads，and the peak stress of specimen shows obvious strain rate effect.In addition，the failure mode of specimens is mainly tensile failure.In the aspect of energy consumption，the dissipative energy of the specimen shows a two-stage linear growth rule with the critical incident energy as the interval point.When the incident energy is less than the critical incident energy，the specimen remains intact after impact.When the incident energy is greater than the critical incident energy，the specimen will be broken after impact and the fragments will fly out.Based on the obtained linear energy consumption rule，two stages of dynamic compression energy dissipation coefficient （DCEDC） are defined respectively.When the specimen is in intact state，the ideal DCEDC is a fixed value，for the red sandstone specimen in this paper，this value is 0.19. When the specimen is in the broken state the DCEDC increases with the increasing incident energy and gradually approaches 0.68.
Fracture rock mass is a kind of engineering rock mass widely existing in nature，which is easy to cause structural failure and instability of rock mass and induce engineering accidents under the action of external force.Therefore，it is necessary to study the crack evolution law and the fracture instability mechanism of rock mass with prefabricated fractures.In this paper，a lot of rock-like samples with prefabricated crisscross cracks were made based on the similarity theory.The uniaxial compression test on the rock-like samples with different fracture length and inclination angles were carried out by using the RMT-150B rock mechanics testing machine，and crack evolution law and fracture characteristics were analyzed.The research results show that the compressive strength of the samples with crisscross crack is significantly lower than that of the intact. The peak stress decreases with the increase of secondary crack length when the principal crack length of the sample is constant. The failure mode of the sample contain crisscross crack with the dip angle are 0° and 60° respectively shows the tensile wing cracks.The failure mode of the specimen contain crisscross crack with the dip angle are 30° and 45° respectively shows the tensile-shear mixed cracks, which have both wing-shaped cracks and se-condary coplanar cracks.
In the process of underground mining and tunnel construction，the rock is mostly in the process of repeated loading and unloading，and the macro-cracks and micro-defects in the rock mass itself will continue to expand under fatigue loading and eventually lead to many accidents.Therefore，it is of great engineering significance to study the micro-defects of fractured rock masses under fatigue loading.In the previous studies, acoustic emission and CT scanning technology were mainly used to reflect the change of microscopic damage through AE number or CT number, which obtained good results.The porosity measured by nuclear magnetic resonance technology can also be used to show the damage of rock samples，but it is currently mainly used in uniaxial compression loading.In this experiment，yellow sandstone specimens with five fracture inclination angles （0°，15°，30°，45°，60°） were selected.Firstly，uniaxial compression experiments were performed to measure the uniaxial compressive strength of fractured sandstone at various angles.Then carry out fatigue loading experiments，and select the upper limit fatigue loading stresses based on the measured uniaxial compressive strength to be 19.1 MPa,25.6 MPa and 30.3 MPa，respectively.The internal porosity of each fractured sandstone before and after 30 fatigue cycles under each upper limit stress was measured with nuclear magnetic resonance instruments.Combined with the analysis of T2 spectrum measured by nuclear magnetic resonance instrument，it is found that with the increase of the upper limit stress，the total area of T2 spectrum and the accumulation of porosity in fractured sandstone have increased significantly.This shows that its internal damage increases with the increase of the upper limit stress，and then combined with the T2 spectral area for quantitative analysis，it was found that the spectral area of the small pores in the T2 spectrum changed only slightly with the increase of the upper limit stress，while the spectral area of large pores increases exponentially with the increase of the upper limit stress.No matter from the angle of the change of the ratio of large pores (to the total pores) to the fatigue upper limit stresses under different inclination angles，or from the angle of the change of the ratio of large pores under different fatigue upper limit stresses to the angle of fracture inclination，similar rules are obtained.Therefore，it can be concluded that the change of large pores is the main factor that causes the total porosity of fractured sandstones to increase after fatigue loading，and then the curve of the ratio of the proportion of large holes to the upper limit fatigue stress ratio after fatigue loading at various inclination cracks is fitted.The fitting coefficients of sandstones at various inclination angles are very high，which shows that the change law of internal damage can be well displayed.Considering the effect of initial damage of rock samples on fatigue loading，two types of damage variables based on the ratio of large pores to total pores were defined to study the impact of fatigue upper limit stress on the fatigue damage of sandstones with different fracture inclination angles.According to the relationship curves between the two damage variables，the upper limit stress ratio and the upper limit stress，the change of the defined damage variable can be well projected. Further analysis can show the intensity change of the sandstones with different fracture inclination angles，that is，the damage intensity of the fractured rock sample that tends to be gentle will eventually be greater than that of the fractured rock sample with a sharp increase in damage. Finally，combining the probability density function of Weibull distribution and generalized Hook’s law，it is deduced from the theoretical formula that it is reasonable to use pores to study sandstone fatigue damage.Combining the results of previous studies and this experiment，it was found that the porosity can well reflect the microscopic damage of rock samples in both uniaxial compression experiments and fatigue loading experiments.
In engineering geology，red clay especially refers to the high plastic clay，which color is brownish-red or brown-yellow and so on，formed by lateralization of exposed rocks of the carbonate system.The red clay sample in this study was taken from 20 m underground in Changzhi area of Shanxi Province，China，which is a special red clay with high pores，high shrinkage and strong hydrophilic properties.The basic physical parameters of red clay were first measured according to the standard for geotechnical test methods（GB/T50123-1999），besides，the mineral composition of the red clay was appraised by X diffraction analysis.The results show that the content of the I/S layer in the red clay is high.In order to study the softening characteristics of the remodeling of red clay and the relationship between shear strength and moisture content，undrained triaxial tests was carried out using the TSZ-2 automatic strain control three-axis instrument.A total of 24 cylindrical specimens were produced during the experiment，each cylindrical sample size is 39.1 mm×80 mm.Because the moisture content of the original soil is about 17.0% to 23.7%，so the moisture content of remodel red clay is 15%，18%，21%，24% respectively.And confining pressures of 100 kPa，200 kPa and 300 kPa were applied respectively at each moisture content.The relationship between moisture content, principal stress difference，cohesion and internal friction angle was obtained from the experiment.When the moisture content changes, the remold red clay of Changzhi area of Shanxi Province have different failure forms.It would have macroscopic shear failure under low moisture content and confining pressure，meanwhile，the stress-strain curve has obviously softening phenomenon, and the modified stress-strain softening model can be better to simulate the test curve.Due to the high mineral content of I/S layer of the remolded red clay in Changzhi area，Shanxi Province，China，so the red clay has a large pore inside，with the increase of moisture content and confining pressure，the specimen from macro-shear damage to plastic damage，besides，when the moisture content is 15% to 24%，there is a linear relationship between the non-draining anti-shear strength and moisture content of this kind of red clay.The research results in this paper can provide reference for the related foundation treatment in the special red clay area of Changzhi，Shanxi Province，China，and also provide a theoretical basis for the further mathematical model of special red clay.
Tailings pond is a man-made source of dangerous debris flow with high potential energy，which threatens the safety of downstream residents and facilities.In recent years，tailings pond accidents have occurred frequently，causing extremely casualties, environmental pollution and bad social impact.In order to reduce the occurrence of accidents，the actual safety of the tailings pond must be scientifically evaluated.Aiming at the problems that complex causes of tailings dam accidents，many influencing factors of safety conditions，and difficulty in determining the proportion of each evaluation index in the whole system，this paper proposes a tailings dam safety evaluation method combining entropy method and catastrophe theory.Based on the “Four Factors”（people，things，management，environment） theory of safety management in system engineering，the safety status of the tailing pond is affected from the aspects of personnel status（A），the status of tailing pond itself （B），safety management（C） and environmental impact factors （D）were decomposed，and an index system of 3 layers and 11 underlying indicators was established.When in use，firstly，entropy method is used to sort the importance of evaluation indexes，and then catastrophe theory is used to calculate to obtain the catastrophe grade value of tailing pond，and finally the comprehensive safety grade of tailing pond is obtained.The method was applied to a engineering project，and the case studies show that the relative importance ranking results of the underlying indicators are：｛A2，A3，A1｝，｛B1，B3，B2｝，｛C3，C1，C2｝，｛D1，D2｝.The relative importance ranking results of the middle indicators are：｛B，C，A，D｝.Then use the normal formula to calculate the total mutation level value is 0.9641，the mutation membership function value is 0.86，means the security level belongs to a safer level.This result is consistent with the results obtained by the expert group，and is in line with the basic situation of the tailings pond.The safety evaluation method based on entropy method-catastrophe theory can be adapted to the safety evaluation of tailings pond.
Mine fan is an indispensable mechanical equipment in mine production，but its performance index in actual operation in the high altitude areas is far lower than the performance standard when it leaves the factory，that is，the problem of fan efficiency reduction occurs.Therefore，selecting a scientific and reasonable method to evaluate the factors affecting the performance of mine fans at high altitude is not only the basis for the selection of mine fans in the high altitude areas，but also the key factor to realize the performance optimization of mine fans in the high altitude areas.In view of the complexity，ambiguity and uncertainty of the factors influencing the performance of mine fans in the high altitude areas，the high-altitude mine fans performance evaluation index system consisting of 4 first-level indexes and 21 second-level indexes was established.On the basis of this evaluation index system of the performance of mine fans in the high-altitude areas，the paper gave each evaluation index weight by using the information entropy theory，thus，the fuzzy comprehensive evaluation model based on entropy weight method was set up.Through the use of the model，the effective evaluation and ranking of the factors influencing the performance of mine fans in the high-altitude areas was accomplished.Taking a mine in Diqing，Yunnan Province as an example for empirical，the analysis results show that the first-level indexes are ranked from the largest to the smallest according to their weight，that is fan structure，environmental conditions，management factors，other factors.Among the second-level indexes，six indexes have a great influence on fan performance.They are air density，the number of blades，blade installation angle，blade thickness，professional training and fan installation form.Moreover，four indexes have a small influence on the performance of the mine fan.They are air temperature，the number of guide blades，supervision of mine fans and selection of fan installation location.In addition，the results in this paper verify the reliability of the fuzzy comprehensive evaluation method on the basis of entropy weight in solving the problem of evaluating the factors influencing the performance of mine fans in the high-altitude areas is verified.These results also provide more solutions for the analysis of the factors influencing the performance of high-altitude mine fans.The results can provide a scientific theoretical basis for the reasonable selection and optimization design of mine fans in the high altitude areas.
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