The development of resources has caused various environmental problems.The implementation of green mining is an effective way to solve the contradiction between economic growth and environmental crisis.In order to avoid the damage to the ecological environment in the process of mineral resources development，the green mining method are adopted in many mines to achieve the purpose of sustainable development.At present，the green mining of domestic mines is still in its infancy.How to evaluate the level of green mining of metal mines scientifically and effectively and determine the evaluation method of green mining is an important problem to be solved at present.The purpose of this paper is to find a reasonable and suitable method for evaluating the green mining of metal mine.Determining the weight of each evaluation index is an essential step in the process of green mining evaluation.First of all，the relevant literature was summarized.The advantages and disadvantages of the commonly used objective weighting，subjective weighting and combination weighting methods were analyzed.Among these weighting methods，the combination weighting method can not only objectively reflect the importance of each index，but also reflect the decision-maker’s subjective desire，and improve the scientific decision-making，which is recommended to use this weighting method in later research.Secondly，according to the existing research results and the characteristics of metal mining，the fuzzy comprehensive evaluation method，extension optimization method，TOPSIS method，factor analysis method，matter-element analysis method and other evaluation methods suitable for green mining of metal mines were summarized.The applicability，evaluation steps，advantages and disadvantages were elaborated in detail.Researchers can choose different evaluation methods according to specific evaluation objects and characteristics.In order to determine the most suitable evaluation method，the above five evaluation methods were prioritized by using expert interview method and grey correlation method.The results show that TOPSIS method has the advantages of no strict requirements for indicators，flexible application，simple mathematical calculation andquantitative objective.Compared with other four methods，TOPSIS method has the highest priority that is the most suitable for green mining evaluation of metal mines.The research results of this paper can provide reference for future research and management suggestions for the government and enterprises.
High quality development and ecological civilization construction are organically integrated and mutually promoted.Green mine is an important way to build ecological civilization and realize high-quality development of mining industry.The evaluation of green mine construction work will not only help enterprises adjust themselves，but also help achieve high-quality mining development.Therefore，it is necessary to evaluate the construction of green mines.This paper used citespace to sort out the existing literature on the number of green mines and the evaluation index system of green mines from 1992 to 2019，and analyzed the three stages of green mine research about the embryonic stage，the development stage and the prosperity stage.The number of papers published at different stages is different，and the research depth is also different.It was also found that there is less literature combining high-quality development with green mines.Reviewing the existing evaluation index system of green mines，it was found that the index system was incomplete and did not reflect the characteristics of the times.This paper explored the internal connection between green mines and high-quality mining development.The construction of green mine is a realistic path for high-quality development of the mining industry，and a concrete embodiment of high-quality development of the mining industry.The high-quality development of mining is the meaning of green mines.Based on the understanding of their internal connection and traditional indicator system，this paper builds a more comprehensive and scientific evaluation index system for green mine construction from the perspective of high-quality development.This system contains four dimensions which are scientific management，resource utilization，modern production and ecological protection.The four dimensions cover 28 sub-indicators.Taking an aluminum mine as an example，the combination method of criteria importance through intercriteria correlation （CRITIC） and order relation analysis method （G1） was used to determine the index weights for green mine construction.This hybrid approach not only avoids excessive reliance on subjective experience，but also overcomes the shortcomings of objective standards that lack empirical guidance.The application of this method increases the accuracy of index system in this paper.In summarize，the article constructs a corresponding index system from the perspective of high-quality development，and combines subjective and objective methods in determining the weights.Further research is needed on how to use the indicator system in combination with the actual situation and which evaluation method will be used subsequently.
It is necessary to do well the waste water produced by mining in green mines.In the surface aeration reactor，the unreacted gas is entrained from the space above the liquid level and dispersed again through the violent turbulence formed by the surface aeration paddle on the liquid surface.Therefore，a series of processes such as separation，purification，compression and recycling of unreacted gas can be omitted by using surface aeration，which is of great significance to reduce equipment investment and operation cost.Waste water treatment using surface aeration is helpful to save energy consumption.At present，there is no research reported on the local property distribution of bubbles in the surface aeration reactor，which is the necessary basis for the accurate design of the reactor.Sharp pictures of bubble motion can be obtained by using the newly developed multi-phase measuring instrument based on the telecentric photography.Then，a series of image processes including enoising，filtering （Gaussian filtering and Median filtering），binarization and in-focus bubbles detection are conducted.Thus，bubble size distribution is obtained and consequently，the specific surface area and bubble holdup distribution are further obtained.Using this method，bubble hydrodynamics in the surface aeration reactor is systematically measured.The axial position and stirring speed are mainly investigated.The results show that the bubble size in the surface aeration reactor is smaller than that in the gas-liquid agitated reactor supplied by the gas distributor.Along the axial direction downwards，the bubble size gradually decreases and the number of bubbles decreases on the whole.This can be explained qualitatively by the different gas dispersion model in surface aeration reactor and gas-liquid stirred tank.The effect of impeller speed is studied on B position.With the increase of the impeller speed from 350 r/min to 450 r/min，the number of suction bubbles increases and the average bubble size increases.In order to strengthen the gas-liquid dispersion process in the surface aeration reactor，two advices are provided：In a shallow bed，zones with fewer bubbles will be greatly reduced.So，such design is more advantageous，and the increase of impeller speed can strengthen the turbulence near the liquid surface and the overall fluid circulation.Thus，it is also appropriate to increase impeller speed within the allowable range of power. This study will provide a new choice for the efficient treatment of green mine wastewater.
Pakistan has a very important strategic position in the the Belt and Road initiative.The China-Pakistan Economic Corridor has penetrated the whole territory of Pakistan，that bring economic dividends to China and Pakistan and more countries of Asia.At present，China’s foreign dependence on non-ferrous metals is increasing year by year.China is urgent to obtain more non-ferrous metals resources and promote the sustainable development of non-ferrous metals industry.The China-Pakistan Economic Corridor is currently a“1+4” cooperation pattern，which include energy，transportation，industrial cooperation and construction of Gwadar Port.It provides a good opportunity for China to cooperate with Pakistan in non-ferrous metal cooperation.However，the construction of China-Pakistan Economic Corridor tends to electric power cooperation and road construction，while the research on non-ferrous metal industry cooperation is less between China and Pakistan.Based on the China-Pakistan Economic Corridor，through a comprehensive analysis of the current situation of non-ferrous metals cooperation between China and Pakistan，it is found that Pakistan is rich in undeveloped mineral resources due to its backward technical facilities，while China is short of metal resources，but the technical facilities for mining are too saturated in China.Therefore，it is necessary to consider the non-ferrous metals cooperation between China and Pakistan.From the perspective of good investment environment，convenient location and transportation，and clear focus on non-ferrous metal development，the feasibility of cooperation is explored，and it is found that non-ferrous metal cooperation has a large space for cooperation between China and Pakistan.The cooperation of nonferrous metals industry can bring more economic benefits and promote the common development of China and Pakistan.Then from the macro point of view，the paper puts forward the international capacity transfer mode of China and Pakistan non-ferrous metal industry cooperation，and from the micro point of view，puts forward three business models, namly production sharing cooperation，business cooperation and technical service cooperation in China and Pakistan.Finally，the paper puts forward three aspects of cooperation guarantee，which are cooperation mechanism，environmental protection measures and risk prevention and control measures based on the new concept of “five links”，in order to implement the cooperation between China and Pakistan’s non-ferrous metal industry，greatly alleviate the pressure of China’s lack of non-ferrous metal resources supply，and help Pakistan improve its national governance ability and improve the livelihood and employment of Pakistan in order to promote the common development of China and Pakistan.
At present，green mine construction is the key task to realize the high-quality development of mining industry in China.Sorting out and summarizing the existing literature is helpful to understand the current situation and development trend of green mine construction，and is of great significance to further guide the green mine construction.This paper used a combination of qualitative and quantitative methods，using CNKI database as the data source，combined with the definition of green mines，the literature measurement tool CiteSpace was used to study the existing literature of green mines.According to the research results，the knowledge maps of authors，authors，research hotspots and core keywords in the field of green mine research were constructed.The following conclusions are drawn：（1）According to the number of papers published，the existing research on green mines can divide into three stages，namely the initial stage of development，the period of vigorous development and the period of stable development.（2）The author’s analysis shows that there are fewer authors engaged in the research of green mines and less cooperation of the research team.There is no effective industry-university-research cooperation relationship between the paper publishing institutions and research institutions.（3）Through analysis of keywords，it can be found that the main directions of green mine research are informatization，digital mines，coal mines and green mine construction.And at this stage，the evolution trend and frontier hotspot of green mine construction research is a reflection of the practical application of Internet of Things and other information technologies in green mine construction and mining area ecological civilization construction.Based on the research results，we proposed the corresponding opinions and suggestions from the perspectives of technology，ecology and policy：（1）The automation，digitization and informatization of mine construction are the main means to promote the construction of green mines.（2）Green mine construction needs to focus on the ecological restoration of mines and the construction of ecological civilization in the field of mines.（3）It is necessary to establish and improve technical standards，management systems and related policy systems，and establish a long-term mechanism for green mine construction. In summary，this paper uses CiteSpace to analyze relevant research literature in the field of green mines.In the context of sustainable development and circular economy，it is necessary to rely on information，intelligence and automation，as well as multi-agent cooperation in technology，ecology and policy.This can improve the efficiency of green mine construction and promote the high-quality development of mining.
The Kumishi region in Xinjiang has low vegetation coverage and high bedrock exposure，which are conducive to ore-prospecting by remote sensing.In order to improve the efficiency of ore-prospecting in this region and achieve a breakthrough in ore-prospecting，we systematically collected data of mine，geology and remote sensing in the Kumishi region.Then we extracted abnormal information of alterations from the ETM+ image by adopting the method of “Mask+Principal component analysis of Crosta+Threshold segmentation.”To check the accuracy of abnormal information of alterations，we compared the extracted alteration information with the field phenomenon of the wall-rock alteration in the Kalatage-Qigebu area and found that it was basically consistent.Based on multi-source information of mine，geology and remote sensing，six ore-controlling factors including mineralized points （ore spots），contact zones of magmatic rocks，alteration zones，faults，anomalies of hydroxyl alterations and anomalies of iron-stained alterations were selected.Since the number of deposits or ore spots in the Kumishi region was not enough to support the data-driven model，the analytic hierarchy process which belongs to a knowledge-driven decision-making method was adopted in this study.Consequently，the hierarchical model for the metallogenic prediction was established by the analytic hierarchy process which can present people’s subjective experience and thinking in digital form and realize the combination of qualitative analysis and quantitative analysis.In this model，the metallogenic prospective prediction was regarded as the target layer.The above six ore-controlling factors were considered as the criterion layer.0~300 m buffers，300~600 m buffers，and 600~1 000 m buffers were taken as the index layer in the lower layer of the first four criterion layers.The last two criterion layers were divided into three grades that were deemed as the index layer.By the combination of some previous research and expertise，some judgment matrices for each criterion layer and each index layer were constructed.In addition，we assigned values to each index layer.On this basis，some weights of each criterion layer and each index layer were calculated by the mathematical method.Meanwhile，the raster calculation and the kernel density analysis were carried out on the GIS platform to complete the comprehensive metallogenic prediction.Finally，some ore spots that were not added to the model were used to evaluate the effect of the metallogenic prediction.To test the accuracy of the predicted results，we drilled two holes in the Kalatage-Qigebu area.The scheelite mineralization in this area was preliminarily found because of the bluish-purple fluorescence of some samples under the ultraviolet light.It was confirmed more precisely by the scanning electron microscope（SEM） and the energy dispersive spectrometer（EDS）.In conclusion，the results show that the application of the analytic hierarchy process in the metallogenic prediction of multi-source information in the Kumishi region has a good effect.Therefore，it can provide some references for further work in this region.
Drilling and blasting is widely used in mining and tunnel excavation as an economical and efficient method of excavation.Among them，smooth blasting is the most common.The theory of smooth blasting theory is based on the concentric uncoupled charge structure.In the actual smooth blasting，the charge structure will change due to the existence of its own gravity, forming eccentric uncoupled charge.The change of the charge structure has made the previous theory no longer applicable，and the earth stress is a problem that cannot be ignored as the depth of the excavation changes.Therefore，in the presence of in-situ stress，the fracture area formed by eccentric blasting is determined to provide a theoretical reference for blasting construction.Because of the eccentricity effect，the uncoupling coefficient of the blasthole is different after charging.According to the definition of the concentric uncoupling coefficient，the equivalent uncoupling coefficient of each point of the eccentric uncoupled blasthole is given.Then based on the theory of blast stress wave and explosive gas，considering the effect of earth stress and the initial damage of rock，combined with the theory of maximum circumferential stress in fracture mechanics，the calculation formula of initial crack and extended fracture under eccentric uncoupling charge was derived.The No.2 rock emulsion explosives and three kinds of rocks were selected as examples to calculate the initial fracture range of the marble，shale and sandstone under the eccentric uncoupled charge，drawing with Origin software.By observing the difference between the coupled side and the uncoupled side，and exploring the influence of the ground stress on the initial crack caused by the explosion stress wave，we compared and analyzed the variation of the initial crack range under different ground stresses.The results show that the uncoupling coefficient on the wall of the blasthole is related to the difference between the deflection angle α，the blasthole and the radius of the lap.The equivalent uncoupling coefficient on the wall of the blasthole hole results in a very uneven distribution of the eccentric uncoupled charge structure，and there is a large difference between the length of the coupling side and the uncoupled side.With the increase of ground stress，the range of cracks around the blasthole is gradually decreasing，and the angle α of the shortest crack on the uncoupled side gradually increases，and its range gradually approaches the radius of the smashing zone.The presence of visible ground stress inhibits the expansion of the crack.The higher the ground stress，the smaller the crack range.When high geostress is encountered in the selected three types of rock blasting constructions，it is necessary to consider the fact that the cracks on the non-coupling side are short or non-existent.The blast holes are arranged in a triangle and the hole spacing is controlled between 0.45 and 0.70 m.
With the rapid economic development，the status of mineral resources in the national economy and the demand for mineral resources has been increasing.In the mining production of these resources，it is an important task to ensure enduring and effective supports，which directly affect the safe production and sustainable development of the mine.Controlling roadway deformation by using appropriate support measures has become a critically important area of focus in the study of rock mechanics and mining.Because the rocks have experienced complex high stresses for a long period of time，the physical and mechanical properties of deep rock masses can change dramatically and the deformation failure modes are significantly different from those in shallow environments.Severe deformations and failures may occur due to high ground stress a short time after roadway excavations，and these may incur large repair costs that seriously hinder the baseline economic development of a mining area.The Jinchuan Mine，the largest nickel production base in China，is located in Jinchang City，Gansu Province.It is a large and complex deposit with high ground stress，a deeply buried ore body，and broken rocks.Due to its extremely complex regional geological background，special engineering geological environment，and distinctive rock mechanics，the Jinchuan Mine has attracted the attention of researchers and experts at home and abroad.Based on the special geological conditions of high-stress and fractured surrounding rock in Jinchuan No.2 mining area，field investigations and numerical simulations were carried out to study the deformation failure characteristics of the roadway in the study area and the effects of 8 different support methods.The results show that：（1）The deformation failure types of roadway in the study area can be divided into six types，including unsymmetrical pressure，roof falling，side cracking，floor heaving，side cracking and rib spalling which is the most common one；（2）The main features of the roadway deformation include large deformation，prominent time effect and the maximum principal stress plays a dominate role.（3）Adding U-shape steel，supplementing bottom support，increasing the length of the bolts，and reducing the distance between the bolts all can improve the support effect to different degrees.The effects of supplementing U-shape steel and bottom bolt-mesh-anchor support are the most significant，which can reduce the roadway deformation and plastic zone by about 70%.Increasing bolt length can control the deformation and overall stability of the roadway better，but the optimization effect is not significant.Reducing the spacing between bolts is beneficial to control the deformation and plastic zone on each part of the roadway.The dense arrangement of bolts can effectively improve the integrity of surrounding rock，and the supporting effect is better after reducing the row spacing of bolts.The aim of the research is providing a reference for other engineering solutions under similar geological conditions.
Huangtupo copper and zinc mine located southwest of Hami City，Xinjiang Uygur Autonomous Region，China.It is an underground mine，and there are several goaves in the mining area.There is another mine nearby the area，which is also mining ore.The mining activities of two mines have caused a great disturbance to the pressure environment in the area.Therefore，MicroSeis microseismic monitoring system was introduced to give early warning of the ground pressure disaster that may be caused by goaves in Huangtupo copper and zinc mine.This system monitors the stability of surrounding rock around the goaves and production area in real-time.The microseismic monitoring system has the advantages of broad range，high sensitivity，non-contact，and multi-parameters analysis.In order to ensure the reliability and real-time performance of the microseismic system，the system was optimized.Using network analysis tools to optimize the best microseismic network layout scheme，than the event positioning accuracy is effectively guaranteed.In this paper，through network analysis，the optimized positioning accuracy of the center practice is about 5 m，and the positioning accuracy of the production operation area is within 10 m，which can fully meet the requirements of ground pressure monitoring and disaster early warning.Microseismic systems always pick up signals in rock masses indiscriminately.However，there are many production noise signals in the general engineering environment，such as blasting signals，mechanical vibration signals，and electrical interference signals.In the aspect of signal recognition，the traditional approach is to rely on manual methods for identification and classification，with low efficiency.Therefore，an artificial intelligence method was proposed to identify the microseismic signals.This automatic identification model ensures the real-time performance of the microseismic system and is the basis of disaster early warning.The early warning method of microseismic monitoring technology is based on quantitative seismology.Moreover，quantitative seismology is based on the development of rock mechanics，seismology，and statistics.In this paper，seismological parameters such as microseismic event activity rate，spatial distribution characteristics，seismic moment，energy，and b value were used to analyze ground pressure activity.At the same time，a set of early warning and analysis methods of microseismic monitoring ground pressure disaster was put forward.This method can realize early warning of ground pressure，provide time for evacuation of mine personnel，and effectively grasp the development trend of ground pressure.Furthermore，it can guide mine personnel to go into the mine for production in a safe time，so it has the significance of popularization in the monitoring of underground mine pressure.
In the process of formation of natural rock-mass，a large number of cracks，holes and other original defects often occur in interior，the internal defects of rock have a significant impact on the mechanical properties of rock-mass.Therefore，it is important to study the initiation，propagation and fracture of cracks in defective rock materials and rock-mass materials for practical engineering.Hence we explored the influence of the change of internal defects from cracks to holes on the fracture mode and characteristics of rock-mass materials by combining theory with experiment.Firstly the mechanical model of uniaxial compression was constructed and the stress at the hole edge was solved by using the conformal angle mapping method，then the uniaxial compression test was carried out on the defective rock samples made of cement mortar materials.The rock-mass specimens were made by mixing 325# white cement，river sand，and water at a mass ratio of 5∶5∶2，the size of the defective sample after forming is 200 mm×150 mm×50 mm.The defects were created by inserting 3D printing materials into cement mortar paste and removing them during curing，the long axis 2a is 40 mm，the short axis 2b is change values for 1，10，20，30，40 mm，hence the corresponding m [m=（a-b）/（a+b）] values were 0.95，0.60，0.33，0.14 and 0.Uniaxial compression of defect specimens by using the rock mechanics servo-controlled testing system after standard conservation were carried out.The test results show that：（1）Under uniaxial compression，when m is 0 the uniaxial compressive strength of the defective rock-mass is the lowest.The uniaxial compressive strength of the defective specimen increases gradually with the increase of m value，and the peak strength of the defective specimen decreases gradually with the increase of m value.（2）In the process of uniaxial compression fracture of defective rock-mass，the initial tension crack is initiated at the end of the short axis of the defect.With the increase of m value，the initiation position gradually moves to both ends of the long axis，and the crack develops along the direction of the principal stress.Under the action of continuous load，shear cracks are initiated near or far from the long axis of the defect，and the shear crack propagates continuously with the increase of load.In the later stage of crack propagation，spalling phenomenon at the end of the long axis when the m value is large.（3）After uniaxial compression fracture the defective rock-mass will have two fracture modes, namely shear failure and tension-shear mixed failure.When m is greater than 0.60，the failure mode is shear failure，others will happen tension-shear mixed failure.
The rock mass of underground mine is a very complex dynamic system，which has many influencing factors.The rock mass quality evaluation is not only an important means to understand the characteristics of underground mine rock mass，but also an important basic data of underground mine design，construction and disaster prevention.The fuzzy and uncertainty of rock mass quality evaluation are strong.Cloud model theory can analyze the fuzzy and quantitative problems，which is very suitable for the random and fuzzy evaluation of multi indexes of rock mass quality evaluation.In order to evaluate the rock mass quality of underground mine more accurately and efficiently，the CRITIC-CW method was proposed，which can quantitatively analyze the fuzziness among many factors affecting the rock mass quality.According to the characteristics of many influencing factors of rock mass quality，rock quality index （RQD），rock uniaxial saturated compressive strength（RW），rock mass integrity coefficient（Kv），structural plane strength coefficient（Kf） and groundwater seepage amount（ω） were selected to evaluate the quality of underground mine and rock mass.20 groups of sample data of rock mass quality evaluation at home and abroad were collected.The original data were standardized，the standard deviation，the correlation coefficient and the amount of information were calculated by using critical method to quantify the discreteness and internal relationship of sample data，and then the weight of each evaluation index was obtained.Based on the CRITIC-CW method，20 groups of rock mass quality evaluation samples were evaluated，and only one case is misjudged，which shows that the CRITIC-CW method has high accuracy and reliability.Xinli mining area of Sanshandao gold mine is the only gold mine under the sea in China.The geological conditions of the mining area and the quality of surrounding rock are complex.In the production process，local pumice falling，roof falling，collapse and other disasters often occur due to blasting vibration，mechanical drilling and other activities，that seriously threatening the safety of mine production.In order to understand the rock mass quality of the mining area better，the CRITIC-CW method was used to evaluate the rock mass quality of some stopes in Xinli mining area of Sanshandao gold mine.The results show that the rock mass quality of the evaluated stopes is mainly class Ⅲ and class Ⅳ，and the rock mass quality is general.According to the results of the rock mass quality evaluation，after strengthening the support for the stopes and surrounding works with the evaluation class Ⅳ，the caving phenomenon of the mining area is obvious decrease.
The room and pillar method is one of the mining methods with high labor productivity, which is widely used in small metal mines.Getang gold mine is located in Anlong County，southwest Guizhou Province，with complex geological conditions.The gold ore body directly covers the undulating paleo-karst erosion surface of the Maokou Formation，and its thickness varies from 0.3 m to 76.0 m.The lithology of the top and bottom of the ore body is complex.In order to design the parameters of underground stope scientifically，analyze the failure mechanism of the roof of the goaf and the bearing mechanism of the pillar，and guide the safe production of the mine，this paper used the theoretical calculation combined with the numerical simulation method to reasonably select the stope parameters and carry out the numerical analysis of the surrounding rock stability of the stope.Through the calculation of the mining span theory，the span of the mine is ≤10 m and the recommended pillar size is 3 m×3 m.Due to the large variation of the thickness of the orebody，the stability of the surrounding rock of the stope should be analyzed under different mine height conditions.In this paper, a numerical model of pillar width of 0.300,0.375 and 0.500 was established by using the finite element Phase 2, and the stability of the surrounding rock in the stope was analyzed by numerical simulation.The simulation results show that when the pillar width-to-depth ratio is 0.300，0.375，0.500，the average stress levels of the floor in the goaf are 12.78，8.04，7.03 MPa.The average stress levels of the rock mass are 19.02，13.03，13.06 MPa.The average stress levels of the roof of the goaf are 10.73，7.20，6.04 MPa；The average stress levels inside the pillar are 28.07，18.62，18.54 MPa；The average displacements near the floor of the goaf are 0.83，0.67，0.62 mm；The average displacement near the rock dam is 2.52，1.27，0.95 mm；The average displacement near the top plate is 8.53，4.73，4.45 mm(maximum displacement is 9.80，5.55，5.27 mm)；The average internal displacement of the pillar are 2.05，0.93，0.68 mm，respectively.According to the com-prehensive analysis，we can conclude that:(1)After the mining，the stress concentration inside the pillar is affected by the supporting pressure，and the floor，rock and roof of the goaf are the stress reduction area；the stress level inside the pillar is the highest near the boundary of the goaf.The stress level inside the rock core is second，and the stress level of the floor and roof of the goaf is the lowest.(2)After the mining，the maximum displacement occurs in the vicinity of the roof of the goaf due to the occurrence of the fracture zone and the plastic zone and the pressure of the overburden. Due to the conduction of support pressure，the displacement value of the pillar from top to bottom is gradually reduced.(3)The maximum stress value and maximum displacement inside the pillar appear at the top of the pillar；The pillar width-to-depth ratio has a certain influence to the stability of the surrounding rock of the stope.With the increase of width-to-depth ratio，the average stress level and average displacement near the boundary of the goaf are reduced，the stress concentration in the pillar is alleviated，and the deformation is reduced. In the process of mining，the size of the pillar should be increased appropriately at the location where the depth of the ore body is large and the thickness of the ore body is large.Keeping the width-to-depth ratio of the pillar at about 0.500 can better maintain the stability of the stope.
As trade friction between China and the United States escalates，international concerns about the creditworthiness of the United States will have a negative impact on the status of the dollar as a national currency，countries may increase their holdings of gold and demand for gold will increase.Myanmar is one of the most promising countries for China’s direct mining investment.The gold resources in Burma are abundant and widely distributed.At present，there are few reports on the development and utilization of gold mines in Myanmar.It is of great significance to strengthen basic research on overseas mineral resources and avoid technical risks.Mineral development investment risk is bigger due to lack of basic materials of process mineralogy of a gold mine in sagaing province，Myanmar.The chemical composition，mineral composition，particle size distribution，physical phase and dissociation degree of gold and structure of ore were studied by means of X-ray diffraction （XRD），scanning electron microscope （SEM） and chemical analysis to find out the process mineralogy characteristics of a gold mine in Sagaw Province，Myanmar.The results show that the grade of gold is 5.13×10-6，which is the main valuable element.The ore has autogenous grain structure，block structure，patchy structure and disseminated structure.The mineral composition of the ore is simple，the metal minerals are mainly pyrite （14.75%），a small amount of chalcopyrite，magnetite and porphyry，and the gangue minerals are mainly quartz，plagioclase，calcite，chlorite and white mica.The distribution rate of gold in heavy minerals is 3.94%.Free gold is hornlike，massive，flaky and circular, the fineness of gold is good （more than 93%）.Gold is easy to dissociate.Most of the gold in the non-heavy minerals has been dissociated，the distribution rate of free gold is 92.68%.The distribution rate of gold parcel is 3.38%.The monomer dissociation degree of fine-grained gold is also relatively high.In the -0.074 mm grain size，The monomer gold content is 98.72%，the adherent-gold content is 1.28%.After 60 h of full-mud cyanidation，the gold leaching rate reached 90.19%，which was close to the rule of gold monomer dissociation degree in the gold mine.It is necessary to continue to strengthen the research on the theory and technology of selecting and metallurgy of a gold mine in shijie province and improve its technical and economic indexes.
There are an abundant gold ores resource in China，and most of gold ores are belong to the refractory ores.The gold in the refractory ores is difficult to recovery by the leaching technology because of the fine dissemination particles in ores.Besides，the natural gold ores usually coexisted with pyrite，arsenopyrite and stibnite and is generally enclosed in these sulfide minerals.The conventional cyanide leaching is difficult to process this gold ore.In this paper，a gold ore from Gansu Province of China contains Au 4.3×10-6，Sb 0.48%，As 0.37% and C 1.84%，which belongs to a refractory gold.The recovery of gold is very low when the ore was directly leached by the cyanide leaching technology.In order to improve the recovery of gold，the gold was recovered in industrial scale by a process combined the gravity separation，froth flotation and cyanide leaching.However，the recovery rate of gold only is 82% due to the gold with a complex dissemination relationship in ores，the gold grade in the final cyanide leaching residue is approximately 0.8×10-6.In order to increase the recovery rate of gold，the occurrence state of gold in flotation tailings was investigated by electron probe microanalysis （EPMA），the flotation tests were conducted in laboratory scale based on the mineralogy results of the flotation tailings.The results indicated that gold in flotation tailings was mainly existed in the formation of lattice gold in arsenopyrite，pyrite and stibnite the or enclosed in these sulfide minerals with the fine dissemination particles size.When the flotation tailings was leached by cyanide solution，the gold enclosed in these sulfide minerals cannot contact effectively with the cyanide solution even if under the very fine grinding fineness.However，the recovery rate of gold was significantly improved when the flotation tailings were firstly sieved before cyanide leaching.After sieving，the coarse particles with the particles size of +0.038 mm was regrinded and increase the liberation degree of pyrite，arsenopyrite and stibnite.After that，the regrinding products was subject to the froth flotation again in order to recovery these sulfide mineral，the tailings after flotation were subjected to the cyanide leaching together with the -0.038 mm fine particles.The recovery rate of gold is obviously increased by 81.3% to 90.21% by using this process，the grade of gold in the final leaching residue is less than 0.3×10-6.The experimental result is helpful for the improvement of industrial production process.
In the process of mine safety production，frequent mine fire accidents have caused huge casualties and economic losses，which has become one of the major concerns.The environment conditions of mines at different altitudes are completely different，which directly affects the evolution of the mine fire，and brings great challenges to the emergency rescue work during the mine fire.Therefore，it is of great practical significance to study the effect of altitude on the law of smoke spread during the mine roadway fire period.In this paper，based on the construction of the mine fire model，the key paramaters of the fire smoke at the characteristic height of the human eye (z=1.6 m) were used as the focus，fire scenarios of the mine mechanical and electrical chamber at five groups of different altitudes from 0 m to 4 000 m（equal points） was simulated by using the Fire Dynamics Simulator（FDS）.By observing the process of smoke diffusion and dynamic temperature rise in different fire scenarios，the law of smoke diffusion and temperature distribution in mine roadway at different altitudes was analyzed.At the same time，the changes of temperature，smoke behavior（CO concentration），visibility and other fire smoke characteristic parameters in the mine fire at different altitudes were compared，so as to analyze the influence of altitude on the safety evacuation of underground personnel during mine fires.The results show that：（1）With the increase of altitude，the rate of smoke spread and the influence range of smoke in the mine fire are correspondingly reduced.In the transverse diction，the effective and safe evacuation route should be far away from the fire side in the tunnel；（2）With the increase of altitude，the characteristic parameters of fire smoke also change to some extent，that is the peak temperature and CO concentration decrease，while the visibility gradually increases；（3）Compared with low-altitude areas，when the fire occurs in the mine with relatively high altitude，the safety evacuation time is prolonged and the safety evacuation distance is shortened，which makes the possibility of people’s safety escape is greater.In general，this paper reveals the mechanism of the effect of altitude on the smoke spread of mine fire，which can be used as reference for the prevention and control of mine fire accidents.
Ventilation of tunneling face is an important part of mine ventilation system，which is of great signi-ficance for guaranteeing the health and life safety of workers.However，the special plateau environment with low pressure and low oxygen has put forward higher requirements for ventilation effect.According to the special environmental requirements of high altitude metal mine and based on analytic network process，11 evaluation indexes were established from three aspects of safety benefit，economic benefit and technical benefit.There is a complex interaction between the evaluation indexes of the ventilation effect of the heading face.The correlation of the evaluation indexes was obtained through group discussion among 12 researchers in the field of mine ventilation.Thus the network structure of ventilation effect evaluation index of heading face was established and the final evaluation system was formed.ANP method involves many elements，the calculation process is complex and the calculation is large.According to the analysis of the ventilation effect evaluation index of the tunneling face of the high-altitude mine and the result of correlation relationship construction，the ANP model diagram of ventilation effect evaluation of the tunneling face was established in the super decision software.The comprehensive weight of three ventilation modes and the global weight of each evaluation index were calculated to select the best ventilation method.This evaluation system was applied to a metal mine at an altitude of 3 400 m in Yunnan.Ten people，including experts in mine ventilation engineering and on-the-job mine ventilation technicians，were invited to fill in the pairwise comparison judgment matrix questionnaire.By comparing the importance of the two evaluation indexes，the judgment matrix was established，and the super decision software was used for relevant calculation.The results show that the comprehensive weight of far-pressing-near-suction ventilation mode ventilation mode is 46.16%，and its ventilation effect is the best.The global weight of “oxygen supply effect” is 20.08%，which is the most important evaluation index.The oxygen supply effect should be taken into account when choosing the ventilation mode of mining face at high altitude.It is proved by practice that the conclusions obtained by the evaluation system are in line with the actual safety of mines，and can point out the main factors to evaluate the ventilation effect of mines.
Low integration，poor sharing，lack of cooperation are the issue in intelligent mine construct of underground metal mine.“1145” construction idea was put forward to intelligent mine construct.Business flow and data flow as clues，construction content which cover all elements and thought-out whole flow is planed based on production technology，production management，process control，safety and environmental protection.Planning content contain information basic platform，production technology collaboration platform，intelligent mining equipment and systems，safety and environmental protection management platform，3D-visualization intelligent control platform.Industrial control network from surface to underground，wireless telecom network and data center are main construction content of information basic platform.The data of other platform and equipment operation are transmitted，stored and shared by information basic platform.Technical operation data and business flow are standardized in the production technology collaboration platform base on 3D mining software.All types technicians can use the same data on the flow.Production technology collaboration platform promotes working procedure and standardization.Production management platform takes the production process management as the core，carries out the whole process management with the production plan，plan execution and result feedback.Material consumption，assay，equipment operation are managed in the same time.Production management platform ensures betimes and sharing，it also provides basic information to manager decision.Intelligent mining equipment and systems can reduce the number of people going down the underground by introducing unmanned equipment.Intelligent mining equipment and systems can reduce the access of construction personnel to dangerous working areas by equipment reformation.Intelligent mining equipment and systems guarantee operator safe and equipment trace scheduling.Virtual simulation training technology and management system introduced in safety and environmental protection management platform.Virtual simulation training technology can effectively reduce the cost of training and improve the safety of operation training.Mobile terminal was used to record site security risk and assign people to deal with the risk in management system.The system can increase efficiency and decrease accident rate on site.The manage process was queried by system.3D digital mine model was established by GIS technology and virtual reality technology on 3D-visualization intelligent control platform.Production management data，safety and environment management data，intelligent equipment operation data was introduced in 3D-visualization intelligent control platform. 3D-visualization intelligent control platform is used to production management and Scheduling.Master plan can provide guidance for the intelligent mine construction of underground metal mine.
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