Matigou-Miaogou gold deposit in Fengxian County，Shaanxi Province is located in the Tangzang-Shangdan tectonic mixed zone of the Qinling orogenic belt.Because of the multi-stage orogenic ductile and brittle tectonic activities，there are many types of superimposed composite shear zones，and deep granite magmatic intrusion during collisional orogeny，which make it an important favorable zone for gold mineralization.The Lower Paleozoic Luohansi Group is a set of shallowly metamorphic and strongly deformed volcanic-sedimentary rocks in the ore-hosting strata of the mining area.It has undergone multi-stage tectonic deformation and metamorphism.Folds and faults are well developed，which make the ore body morphology complex and can be roughly divided into north-south tectonic belts.The shape of folds is complex and varied，and the overall shape of folds is reversed S-shaped，while the fracture is a series of brittle-brittle toughness with multiple primary and secondary matching.This paper uses the research methods of structural section and slice of rock and ore in the mining area，based on the field geological facts，through the special study on hierarchical classification of the mining area structure，detailed research on various types of ore-controlling structure styles and features in the area.Combined with the methods of rock slices，petrochemical analysis and deep exploration of prospecting engineering，the history of regional tectonic evolution，divided different levels of ore-controlling structures，a four-level ore-control structure was divided.Structural profiles show that tight folds and other ductile shear deformation and dynamic metamorphism such as mylonite zone and schistosomiasis zone are developed in the mining area.Rock （ore） slices show that mylonite foliation displacement early regional foliation （phyllite，etc.） is widespread in the mining area，which can reach above the level of primary mylonite，and is multi-stage brittle and ductile superimposition transformation.Gold mineralization is related to ore type and fabric.Gold grade of alterated mylonite （10.2×10-6~17.5×10-6，weathered：4.97×10-6~6.23×10-6），especially superimposed quartz vein type，is higher than altered cataclastic rock （1.16×10-6），rock mass and boundary contact zone with the lowest grade （0.18×10-6~0.89×10-6），and is mineralized.The study concluded that there is a stripping fault before the metallogenic period.Matigou-Miaogou gold deposit is a fourth-order tectonic ore-controlling zone and a first-order Tangzang-Shangdan tectonic melange zone，which controls the distribution of metallogenic belts and ore-forming geological bodies in the area，i.e.the north-south tectonic slices and Jingshaowan back-shaped.The second-order is a nearly east-west-trending Luohansi-Wayaoshang brittle-ductile fracture（F9），which retains the characteristics of multi-stage compression brittle-ductile structure from north to south，and the section develops tectonic slices，it controls the spatial location of mineralized alteration zone.The third level is F9 which controls the NWW-NW secondary derivative brittle-ductile shear zone，which is nearly parallel to it，and controls the spatial form of ore bodies.The fourth level is the position where the occurrence of shear zone changes and the extensional fracture zone，which controls the occurrence change of orebodies and the changes of ore grade and type，such as thickening and quartz vein type superimposition and enrichment.The main ore-controlling structure extends in the direction of nearly east-west and northwest-west.The orebody dips northward gently and steeply locally，and is controlled by the vertical schistosomiasis zone of northward dip.The space may be in the form of multiple folds or fold stacks.The main gold metallogenic bodies in this area formed hydrothermal alteration and enrichment in the process of brittle-ductile shear deformation in the late Indosinian period，superimposed by enrichment of gold-bearing quartz veins in the extensional fracture zone of shear zone.The metallogenic type is Late Triassic brittle-ductile shear zone superimposed extension fracture hydrothermal gold deposit.
Phabon gold deposit is located in Phabon Village，50 km north of Luang Prabang City，Laos.Six gold orebodies were discovered in Phabon gold deposit，which has reached the large-scale gold resources according to the current level of exploration.Phabon gold deposit is in the “Sanjiang” metallogenic belt in Yunnan Province，which has the favorable metallogenic conditions.It is hosted in the Permian limestone and controlled by a NW-trending fault system.There are three types of primary ore and the ore-forming period is disseminated type，breccia type and auriferous calcite vein.The breccia type is with the highest grade，followed by disseminated type，and auriferous calcite vein with the lowest grade.This study explores the phenomenon of “coexistence of front and tail halos” by studying the vertical projections of the V-1 main orebody and the structural superimposed halo characteristics，which indicates that there are multiple stages of ore-forming activities，and the degree of denudation of orebodies is small.The extension is large and there may be blind orebodies in depth.At the same time，the anomalous concentration center of different ore-forming elementis distributed in the south-east direction，so it is speculated that the migration process of ore-bearing hydrothermal fluid alonging the tectonic fracture is from bottom to top and from south to north，which provides geochemical basis for the determination of lateral law.The spatial distribution characteristics of the different level of the V-1 main orebody and a series of parallel veins distributed by the left geese，and the ore-controlling microstructures shows that the Phabon gold ore vein has the rule of the lateral trending towards the southeast side.In addition，through the analysis of the pre-existing temperature measurement of the fluid inclusions in the metallogenic period of the Phabon gold mining area，parts of the mineralization temperatures are higher than 300 ℃.It is speculated that the genesis of the deposit may be related to magmatic hydrothermal fluid，and the ore-bearing fluid may be related to magma，atmospheric precipitation，surface water，etc.At the same time，high-grade native with realgar and orpiment can be seen in the 500 m depth of borehole.All of them are believed to have the potential to find sulphide-type gold orebodies and rich veins in the depth of the Phabon gold mine.The above conclusions provide theoretical guidance for prospecting and increasing gold resources in the depth and explorating parallel orebodies in the future.
The western tungsten deposit area of Zhen’an is located in the south Qinling tectonic belt.The main exposed strata in the area are Paleozoic carbonate rocks.The magmatic rocks are mainly rouge dams，lazy benches and Sihaiping granite bodies.The fault development in the area provides a ore-conducting and ore-bearing structure for the tungsten ore formation in the area.The skarn-type tungsten mineralization occurred in the near EW strike fracture zone.In addition，the NE-NNE-oriented quartz vein-type tungsten mineralization also developed，which together constitute the main tungsten-molybdenum mineralization type in this area.This paper mainly conducts field investigation and indoor research on typical tungsten deposits such as Qipangou and Hetaoping in the mining area，and has obtained the following knowledge：（1）The ore-controlling structure in the ore-concentrating area is a tectonic fracture in two different directions from the EW and the NE-NNE direction.（2）According to the tectonic background of the area，the tectonic fractures in the NE-NNE of the ore-concentrating area are formed by the Late Indosinian-Yanshanian tectonic activities，and the near-east tectonic fractures are mainly formed by the Indosinian tectonic activities.Compared with the Yanshanian tungsten-molybdenum ore-forming period，the near-east-west fault is a pre-mineral structure，while the NE-NNE fault fracture belongs to the metallogenic structure.（3）The type of tungsten mineralization in the ore-concentrating area is mainly composed of hydrothermal quartz vein type and fault-controlled skarn type.The quartz vein type is mainly controlled by the NE-NNE fault and joint fissures, and the skarn type is mainly controlled by the near-east-west fault fracture zone.
The average dip angle and thickness of a silver ore body are 70 degrees and 10 m respectively.The ore body is unstable and the surrounding rock of the hanging wall and footwall wall is relatively stable.In order to determine the optimum stope structure parameters and optimize the safety and economy of the mining scheme，a Vague-RSM-AFSA model was established to optimize the stope structural parameters.Fifteen schemes of stope structural parameters were designed based on the principle of central composite test method，and the numerical model of each scheme was established by Midas coupled FLAC3D. Stope structural parameters are related to the safety and economy of mine production.The maximum settlement displacement of stope roof，maximum horizontal displacement of pillar，mining-cutting ratio and the ore loss rate were selected as evaluation indexes based on the geological conditions，mining methods and other factors.The Vague theory can accurately express the fuzziness and uncertainty of information，the weight of each index was obtained by calculating Vague entropy of each index.Based on Vague set，the positive and negative ideal schemes within the optimum range of stope structural parameters were obtained，and the superiority of each scheme was calculated by Euclidean distance method.Response surface methodology （RSM） can accurately construct the complex non-linear response relationship between independent variables and dependent variables，response surface method （RSM） was used to establish the response surface model of stope structural parameters and superiority of various schemes in central composite test.The square R 2 of the fitting correlation coefficient of the model is 0.9766.The numerical analysis of three groups of structural parameters in the optimum range but not in the central composite test was carried out.The maximum error between the results and the response surface model is 0.0213，which shows that the established response surface model has high accuracy.Artificial fish swarm algorithms （AFSA） has a strong ability to search global extremum，and can effectively solve complex non-linear multi-objective optimization problems，the artificial fish swarm algorithm （AFSA） was used to optimize the superiority response surface model.The optimum stope structure parameters were obtained as follows： 20 m for stope height，32.8 m for stope length，16.1 m for pillar width.And the superiority is 0.2631，which is higher than the maximum superiority of 0.2271 in the central composite test，and the error between the optimization results and the numerical simulation results is 0.0037. It shows that the Vague-RSM-AFSA model has good optimization ability and high accuracy，which provides a new method for the optimization of stope structural parameters.
After more than ten years of underground mining in a quarry in Liuyang City, a gob group was formed by four irregular goafs, and the gobs were close to the surface with a running county-level Jiuxi highway.In order to develop the next-stage mining plan and ensure the safe operation of the above-mentioned roads and the quarry, it is necessary to comprehensively analyze and judge the stability of the goaf group and the overlying road.Field surveys about occurrence condition of goafs, hydrogeology survey as well as engineering geometry survey were performed.On-site point sample loading experiments and indoor rock mechanics experiments were made and basic mechanical parameters of surrounding rock were obtained and then the chart of the discrete strength parameters of the rock was used to analysis the quality of rock mass.After that,the required strength parameters for numerical analysis were calculated out with the method of Hoek-Brown principle as well as some amendments of related strength parameters.Then, numerical model about shallow buried connected goaf groups of the quarry formed after mining as well as highway on topsoil over the goaf group was built to evaluate the stability of goafs and highway so as to bring forward corresponding measures.After the initial geo-stress simulation and the formation of the goafs, in order to explore the impact of the driving load on the goaf, the driving load is applied to the road surface in the form of normal pressure, and then calculated to balance.Comprehensive evaluations on stability of goafs show that goafs are basically in stable condition and the goafs have little influence on overlying highway.The results also indicate that the highway is generally stable with partial separation of layers.Due to the spatial distribution characteristics of the goafs, the subsidence curvature caused by the uneven settlement and the local separation of road layers are harmful to the highway.The distribution of separation zone presents the characteristics of overall dispersion and local concentration, that is, unevenly distributed local strip-shaped separation zone. To ensure the safety of goaf and healthy running of highway,disposal measures for goafs and the road were proposed.Overall, the relative spatial position of the highway and the goafs and the surface topography of the surface play a major role in controlling the damage form of the highway.To ensure the safety of the road and avoid the activation of the goafs.Finally, it is recommended to backfill the 4# goaf to reduce the non-uniformity of spatial distribution and reinforce the separation part of the road by local grouting.
On the premise of ensuring safe production，efficient exploitation has become an important mode of urban mining resources exploitation and utilization.The mining activities in urban underground mines will cause the stress field redistribution and displacement deformation of the upper and lower layers and surrounding rock masses.Langya Mountain copper mine in Anhui Province is a typical urban underground mine， dangerous accidents such as ground subsidence and structure collapse caused by mining must be avoided.Taking mining methods and techniques optimization as a goal，three mining method were put forwarded，which are upward horizontal cut and fill method，two-step open stope afterwards back-filling mining method and upward high stratification filling mining method.MIDAS GTS NX three-dimensional numerical calculation model of ore bodies based on the three mining methods was established.12 surface monitoring were decorated by using FLAC3D software to simulate the orebody in -365 m to 245 m middle section，Langya Mountain copper mine.Orebodies in different mining methods under the condition of stope mining and surface stability was researched，and the surface tilt，curvature and level displacement deformation parameters was calculated.On this basis，three schemes are evaluated and optimized by entropy weight according to the comprehensive mining technical and economic indexes.The results show that：（1）The distribution of the settlement area extends evenly and outward in a circle，and the settlement trend is consistent with the strike of ore body.According to the deformation data of 12 monitoring points of three mining schemes，the monitoring surface settlement displacement and horizontal displacement of each point are U-shaped distribution affected by the distribution rule of ore body，and the maximum deformation reaches 25 mm.（2）The displacement inclination，curvature and horizontal deformation calculated at monitoring points with dense surface buildings meet the safety requirements，and with the maximum values of 0.099 mm/m，0.17×10-3 ·m-1 and 0.0248 mm/m，respectively.（3）The calculated surface deformation indicators are scored by experts，and the scoring results of surface indicators and technical and economic indicators are normalized.The comprehensive evaluation index values of three different schemes are obtained in the model of entropy weight method，and the evaluation results show that plan 3 is the optimal scheme.The coupling of numerical simulation and entropy weight evaluation integrates the objective data and fuzzy evaluation，and makes scientific and reasonable comprehensive evaluation of different mining methods，thus putting forward new ideas and directions for the comprehensive evaluation of urban underground mines.
Xinli mining area of Sanshandao gold mine is the only undersea metal mines in China，its mining technology demand is higher，and also have serious security problems.At present，at home and abroad，the research on the prediction of rock mass movement and surface subsidence caused by coal mining is relatively mature，and a variety of practical subsidence models and realistic surface subsidence prediction methods are formed.However，most large and medium metal mines are mined using filling methods.The effect of repeated mining not only makes the mines face new deformation and damage of the filling body，and with the continuous expansion of the scale of the filling body，the large-scale deformation and destruction of the filling body further complicates the movement of rock mass.Finally，threatening the safe production of mines.With the popularization of filling mining methods，the law of rock mass movement and surface deformation caused by filling mining has become an urgent problem to be solved.The in-depth study of this problem can provide the basis for rock movement and surface settlement for the safe mining design of submarine mines，and provide a conceptual model for the prediction of rock mass movement and surface settlement caused by mining.So，grasping mining-induced movement rules of overburden above goaf and realizing valid predictions for overburden movement are the problems to be solved for Xinli seabed gold mine.The monitoring of the displacement of rock mass is a direct means to study the movement and deformation of rock mass caused by inclined orebody mining.The movement and deformation characteristics of inclined overburden in mining by filling method are obtained by monitoring the displacement of roof of each level of the 55 lines underground in Xinli mining area.On this basis，the paper firstly proposed a cantilever mechanism to explain movement and deformation in overburden rocks triggered by cut and fill mining method in metal mines with inclined veins.Based on the analysis of the displacement monitoring data of roof，and according to the characteristics of the displacement curve，the profile functions method is proposed to predict the subsidence of inclined overburden in mining by filling method.The method consists of several exponential functions and the subsidence curve obtained by this method is very close to the measured results.And the accuracy of the prediction is all above 85%.Therefore，the research results have important guiding significance for the safe production of submarine mines.
Sanshandao gold mine is divided into two mining areas.One is the Xishan mining area，whose orebody is buried on land,the other is the Xinli mine area.It is the only undersea metal mines in China，its mining technology demand is higher，and also have serious security problems.Among them，the clay aquifer of the Quaternary bottom and F1 fault mud are the key parts of water blocking，and the two aquifers will cause seawater to break into.Therefore，it is necessary to ascertain the geological conditions of the overlying strata in the mining area，especially the distribution of the clay aquifer.After exploration，high precision three-dimensional seismic exploration technology including flexible acquisition geometry，low noise receiver conditions and quantitative control has been formed.The foundation of 3D seismic exploration technology is 2D seismic exploration technology.3D seismic exploration is more accurate and spatially stereoscopic than the data obtained by 2D seismic exploration，but it also has higher requirements for the exploration environment.This paper briefly discusses the difficulties and countermeasures of exploration，the layout and data collection of exploration lines，the fine interpretation of the overlying layer and the hydraulic connection between the overlying strata and seawater.In the submarine seismic exploration in the Xinli mining area，good results have been achieved，as follows：In the geological exploration of mining areas，the 3D seismic exploration method can accurately detect the geological structure of shallow and deep in a large depth range，which is an effective and practical technical method.In this submarine seismic exploration in the Xinli mining area，good results have been achieved.The specific understanding is as follows：The Quaternary is stably distributed in the detection area，buried in depth of 8～39 m，which is mainly characterized by the thinness of the stratum in the west and the north and the deepening of the stratum in the southeast.Among them，the thickness of clay aquifer at the bottom of Quaternary varies in the range of 1～11 m，and the distribution trend is basically the same as Quaternary.But it thins obviously near the F1 fault，the thickness is 2.5～5.0 m，and thins gradually to the north-west direction，and the stability of aquifer becomes worse，which has a certain risk to the mining of the deposit.The total thickness of the weathering zone of the underlying bedrock in strong，medium and weak layers varies in the range of 3～35 m.The weathering zone near the F1 fault is obviously thicker，with a thickness of 20～35 m，which is the main permeable structure in the mining area.High-precision three-dimensional seismic technology was first applied in the geological structure exploration of the Xinli mining area，which provided data support for the safe mining design of the submarine mining area of the Sanshandao gold mine.
Mine water inrush is one of a major problem in the process of mining，and it is also a key technical problem in seabed mining.At present，the study on the potential dangers of water gushing and inrush in the mining of submarine metal deposits in China is still in its infancy，and there is no mature experience to draw lessons from.Therefore，this paper has made relevant research on the risk assessment and safety early warning system of seawater intrusion in seabed metal deposits.In the first，in view of the uncertainty and randomness in the risk assessment process of submerged gold mine water，an evaluation index system is established by selecting 10 important factors in geological and hydrological conditions.The factors are RQD value，joint spacing，rock permeability coefficient，structural plane condition，in-situ stress，water inrush volume，seawater proportion，brine proportion，atmospheric precipitation ratio and absolute value of seepage temperature difference.In the second，based on the evaluation results，the phase space of the time series of water inflow in dangerous areas is reconstructed，and meanwhile，the parameters of reconstructed phase space are obtained by G-P algorithm and autocorrelation method.What’s more，the evolution law of phase distance of water inflow is also analyzed，and then the early warning mechanism of water inflow safety is established.Combining with the reconstruction of chaotic phase space，the RBF neural network model for forecasting water inflow is established.Finally，after 6 000 training iterations，the model meets the training requirements，which is used to compare the simulated value with the actual value.It is found that the predicted result of water inflow within 13 days is basically consistent with the actual value，with the maximum error of 1.48%.After more than 13 days，the prediction effect becomes worse and worse.Therefore，the chaotic neural network model can be used to make a more accurate prediction of water inflow in a short time.The final research shows that the evaluation results of cloud model for water inrush risk are accurate and reliable.On the one hand，the phase space reconstruction reveals the chaotic characteristics of the system，and the evolution of the nearest phase points enlarges the intrinsic subtle variation characteristics of water inrush volume，which provides a basis for the establishment of early warning mechanism for water inrush safety.On the other hand，the chaotic RBF neural network can achieve short-term accurate prediction of water inrush volume and provide technical guarantee for underground safe mining barrier.
The rock mass contains a large number of complex fracture forms，which have a great impact on the strength and stability of the rock mass，making the rock mass show obvious anisotropy，and thus affecting the safety and stability of civil engineering structures.The common crack forms in rock mass are parallel，cross and intermittent and complex form of these three crack combination forms，and so on.While previous researchers’ study of fractured rock mass were more focused on the common fracture forms such as parallel，intersection and discontinuity.But in practical engineering，the rock mass cracks are mostly complex cracks formed by different combination of fracture forms，such as parallel and intersection joints forming N-shaped joints，and the stress and failure characteristics of N-type joints are more complex than that of single fracture form，and have a greater influence on strength and deformation of rock mass.Aiming at the stability problem of surrounding rock in underground engineering such as tunnels and roadways， the stability of rock mass with N-shaped fractures combined with parallel and cross fractures were studied，taking the N-type joints formed by the combination of 45 degree inclined main joints and two parallel joints as the research object，and the multi-repeated failure modes of tension-shear and compression-shear of rock mass under the combination of parallel and cross-fissures were studied.The influence of different primary and secondary joint angles on rock mass strength and failure mode was analyzed，which provided theoretical support for the design，construction and safety evaluation of underground geotechnical engineering.Uniaxial static load test and ultrasonic test were carried out on the cube specimen of cement mortar with side length of 150 mm，strength of 10 MPa and prefabricated with N-type joint，to obtain their stress strain，failure forms and ultrasonic data.Combined with fracture mechanics theory，it is concluded that the strength and deformation characteristics，the ultrasonic wave velocity attenuation law and failure mode （Ⅰ，Ⅱ crack type crack and extend the features） of N type joint rock mass.The results show that firstly the crack types of N-type composite jointed rock mass have wing crack and secondary inclined crack in sequence，and their propagation paths tend to be in the direction of main stress eventually，which is different from the crack development law with single jointed rock mass.There is a nonlinear relationship between stress intensity factor at the tip of the main joint and the load P and fracture angle θ 0.When θ 0 is small and P is close to the peak strength，the specimens mainly propagate in mode Ⅱ crack shape，while mode Ⅰ crack morphology is more obvious when θ 0 is larger.Secondary the average ultrasonic wave value of the specimens with joint angles ranges from 2.463~2.699 km/s，which is quite different from the ultrasonic wave velocity of the complete specimens （2.725 km/s），indicating that the existence of joints accelerates the internal damage of the specimens.When the inclination angle of the main joint is constant，the angle between the main and secondary joints and the number of joints has some influence on the physical properties of the specimen.The attenuation rate of each group of joint specimens is from 0.9% to 9.6%, the velocity attenuation of joint specimens with angle of 15 and 90 is the fastest，while that of joint specimens with angle of 60 is the slowest.Thirdly the constitutive relationship，peak strength and failure characteristics of composite jointed rock-like mass all show nonlinear characteristics.The distribution law of peak strength basically obeys M-type distribution，which is different from U-type distribution with single joint.Among them，the quasi-brittle failure occurs at the angles of 15，30，45，75，90 degrees and the complete specimen，while the brittle failure occurs at other angles，this may be caused by discrete of the specimens.
Seldom scholars have investigated the strain and stress state of mineral particles in the rock on the microscopic scale in experiment.At the same time，due to the complex shape of the internal particles of the rock，it is necessary to find suitable research methods and high-precision research instruments.Therefore，for quantitative research on the plastic strain and stress of mineral grains in sandstone under uniaxial compression，X-ray CT was used to scan three-dimensional structure for sandstone (spatial resolution of 4.6 micrometers) to investigate the movement behavior，and put forward the method of deformation gradient tensor calculation of mineral particles to investigate the plasticity of the grains and conduct statistical analysis of the results.Firstly，the displacement of sandstone mineral particles is extracted.At the same time，non-local means filtering algorithm is used to denoise images of sandstone.Then，based on the three-dimensional structure of sandstone，different mineral components are segmented.The principle strains and stress are obtained by and the deformation gradient of sandstone mineral particles.The results show that the filtering algorithm has a significant improvement effect on the CT image of sandstone.In addition，based on the X-ray CT in-situ test results of sandstone，there are relatively complex strain behaviors and stress responses in the sandstone，and significant differences in the deformation behaviors between the fracture zone and the non-fracture zone.Rock grains in Z axis direction experience compressive stress，and in the XY plane are under the effect of tensile stress.At the same time，mineral grains exist larger plastic strain，and the internal grains test of strain and stress is greater than strain and stress the sample at macro-scale.The grain plastic strain in the fracture zone and the non-fracture zone is about 30 times and 5 times bigger than on the macroscopic strain of the sample respectively，which indicate that the deformation behavior in in the microscopic of red sandstone is significantly different from that in the macroscopic sample.This method plays an important role in revealing the internal structure of rock mass and the evolution process of stress and strain state.
For underground mining，the reserved blasting layer for secondary blasting can ensure the contouring effect of the roadway face and reduce the surrounding rock damage.When using the reserved photo-explosive layer for roadway blasting，the influence of the initial stress field redistribution on the blasting crack propagation，the damage of the inner ring blasting to the reserved photo-explosive layer，and the stress wave during the blasting of the photo-explosive layer should be considered.Based on the interaction theory of ground stress，stress wave and explosive gas，the parameters of the secondary blasting of the reserved photo-explosive layer are optimized.The influence of the thickness of the reserved photo-explosive layer on the redistribution of ground stress and the influence of the secondary stress on the crack propagation of the explosion are analyzed.It is known that the secondary stress will inhibit the crack propagation and the thickness of the photo-explosive layer and the secondary stress are positive correlation，therefore，in the construction of the project，the thickness of the photoburst layer should be reserved for the secondary blasting.The thickness of the blast layer should not be too large.The analysis should not consider the damage，consider one damage and consider the double damage conditions，the axial non-coupling coefficient and the blasthole.The change in the size of the gap makes it possible to appropriately increase the axial uncoupling coefficient and the blast hole spacing in consideration of the damage.Taking the deep mining project of Jiaojia gold mine as the background，compared with the blasting effect before and after the optimization of blasting parameters，it can be seen that considering the ground stress and damage in deep mining，the porosity and cost can be improved.The research results provide a theoretical basis for the standardization of underground mining blasting，which can provide reference for similar projects.
In recent years，due to the impact of Fukushima nuclear leakage accident，the price of natural uranium has continued to decline，and more and more uranium mines have gradually attached importance to the utilization of resources.Muckpile is the smallest mining unit in open-pit mine.Finding out the grade distribution in muckpile is very important for blasting charge，network connection design，ore block design and shoveling operation.At the same time，it is very important to reduce dilution and loss and improve resource utilization. Grade estimation of muckpile is an extremely important routine work in open-pit uranium mines.In order to get the grade estimation results quickly and accurately，the basic principles of the nearest neighbor method，the inverse distance weighted method and the ordinary Kriging method are introduced.Taking a foreign uranium mine as an example，the bench height of the open-pit uranium mine is 7.5 m.The bench is divided into several muckpiles by single bench mining.The blasting hole grid is about 6 m×6 m.Gamma logging is used to obtain the grade information of each blasting hole in the ore-bearing muckpile.The logging interval is 0.1 m，that is，the original sample length is 0.1 m，and Gamma logging is not carried out in the pure waste muckpile.Using three-dimensional mining software，four muckspiles were selected to carry out grade estimation experiments.Based on the estimation results of the ordinary Kriging method，the deviation，statistics and graphical analysis of the estimation results of the nearest neighbor method and the inverse distance weighted method were carried out successively.The results show that the deviation of the inverse distance weighted method is generally smaller than that of the ordinary Kriging method in ore quantity and average grade，the maximum deviation of ore quantity is only 6.19%，while that of the nearest neighbor method is generally larger，and the maximum deviation of ore quantity is 27.6%.The accuracy of the nearest neighbor method is close to that of the ordinary Kriging method，and the accuracy of estimation meets the requirements of actual production of mines.It can be used to estimate the grade of muckpile.However，the nearest neighbor method has a relatively poor estimation accuracy and can not be used to estimate the grade of muckpile.The inverse distance weighted method，as a grade estimation method of muckpile，has a simple operation process and relatively definite parameters，which can save a lot of time while satisfying the requirement of estimation accuracy.The research results can provide guidance and reference for similar open-pit uranium mines to estimate the grade of muckpile.
As the mining depth continues to increase, the pressure management of the stope and goaf is becoming more and more difficult.In order to maintain the stability of the stope,ensure the safety of the operation and prevent the collapse of the goaf,the filling method has become the preferred method for underground mining and has been widely applied.The filling method is to fill the filling body in the goaf to form a filling body with a certain compressive strength, and then carry out underground management by the supporting action of the filling body.Therefore, in the process of mining using the filling method, it is the key to efficient and safe mining of the mine to prepare the filling slurry with reasonable ratio and considerable economy to ensure that the compressive strength of the filling body can meet the needs of ground pressure management.However, there is no simple linear mapping between the filling ratio and the compressive strength of the filling body, and it is usually difficult to calculate by general mathematical methods.To this end, many researchers have conducted a lot of research on the ratio of filling slurry and the optimization of compressive strength of the filling body.Most of these studies only consider optimization under single-objective conditions, and there are few studies on multi-objective conditions.Therefore, other methods should be found to carry out multi-objective optimization research. In this paper, based on artificial neural network and genetic algorithm, a new optimization method of filling ratio is proposed.Firstly, the parameters of cement filling ratio, fly ash mass fraction and tailings mass fraction were optimized parameters, and the backfill strength was used as the optimization target to establish a BP neural network of 3-9-1.The BP neural network is optimized based on genetic algorithm, and the GA_BP neural network with higher prediction accuracy was established.Then,the GA_BP neural network with higher prediction accuracy is used as the fitness function, combined with the cost calculation function, and multi-objective optimization is performed by genetic algorithm to obtain the optimal filling slurry ratio parameter.The results show that when the compressive strength of the filling body is 1.5 MPa, the cement mass fraction is 8%, the fly ash mass fraction is 2.3%, the tailings mass fraction is 66.3%, the cost is the lowest, and the lowest cost is 29.3 yuan/t.The optimization results are consistent with the actual situation.
The grade of high-altitude complex copper oxide flotation concentrates treated in a large-scale concentrator in Tibet was unqualified，and the recovery rate was not satisfactory.Through the study of mineralogy of minerals，the embedding characteristics of metal minerals and gangue minerals was obtained.The secondary copper ores with high copper content as well as the mineral arsenic bismuth copper ore are closely embedded with pyrite，where a mixture of copper and iron minerals often forms，which can affect the quality of copper concentrate and the recovery rate of copper.There are a certain amount of muscovite，feldspar，gypsum and calcite in the ores.Muddy phenomenon is prone to occur during the grinding process，which can affect the copper mineral floating.Thus，the optimization of grinding fineness and flotation reagent system for this refractory oxide copper ore was carried out in this study.On the spot，a large amount of lime was added，and the pH value was adjusted to 11 using high alkalinity to inhibit the rise of pyrite.From the study of process mineralogy，it was known that pyrite was dissolved by pyrite，and pyrite was suppressed at the same time.It will affect the rise of copper minerals.The new drug T506 is an inhibitor developed for the characteristics of pyrite.This inhibitor interacts with the surface of pyrite by adjusting the arrangement of polar groups to achieve the effect of inhibiting the rise of pyrite.The laboratory closed-circuit test was conducted in condition of the copper oxidation rate of ore is 36.80%，where combined copper oxide is 16.59%，copper grade is 0.51%，gold grade is 0.25×10-6，and silver grade is 14.24×10-6.In the selection process，the new inhibitor T506 is used to replace part of the lime in the rough selection section，and the amount of sodium sulfide is appropriately increased.On the basis of ensuring the pH value of 11 in the selected operation section，the amount of T506 is increased in an appropriate amount to obtain a concentrate with a copper grade of 19.72%，a gold grade of 2.66×10-6，a silver grade of 300.36×10-6， a copper recovery rate of 65.50%，a gold recovery rate of 18.36% and a silver recovery rate of 35.92%.The concentrate grade increased by 9.18% compared with the one in on-site production conditions，and the copper beneficiation recovery rate increased by 4.87%.Under the premise of ensuring the qualified copper grade of the produced concentrate，the recovery rate of copper is correspondingly increased，and the purpose of increasing the economic benefits of the enterprise and comprehensively utilizing valuable mineral resources is achieved.
Identified the project risks of transnational mining M&A，and established an evaluation index system including four grade Ⅰ indexes and eleven grade Ⅱ indexes，which was applied to a case，and the evaluation results are consistent with the fact.Thus，it provides a more scientific evaluation standard for the project risk evaluation of transnational mining M&A.It is known that risk identification is very important to establish a project risk evaluation index system，index grading is the basis which should be considered according to the data issued by the authority and the accepted classification rules，and the number of qualitative indexes should be reduced to make the results more objective.A TFN-RS empowerment model was established，that is，using the triangular fuzzy number theory to determine the subjective weights，using rough set theory to determine the objective weights，which solves the existing problem of single subjective or objective empowerment，so that the weight empowerment is more scientific.It is shown that the weights of the geological resource conditions and the economic benefit conditions are relatively larger，29.79% and 29.82%，respectively.Therefore，in the process of transnational mining M&A，obtaining resources and economic benefits are the main motives.In terms of grade Ⅱ indexes，the service life，infrastructure and internal rate of return are the most important indexes.This paper established a project risk evaluation model for transnational mining M&A based on the cloud and matter-element theory，which can better solve the fuzzy problems of the risk level’s boundary division and quantitatively evaluate each project risk level.It is conducive to the further identification of risk factors and the development of risk control strategies.Applied the established risk evaluation model into a case，it shows that the combination of TFN-RS model and the cloud matter-element model is one of the effective methods to evaluate the project risks of transnational mining M&A.It showed that the mining technology conditions and the geological resource conditions of the project are in a “lower” risk level，the external construction conditions are in a “general” risk level，the economic benefit conditions are in a “low” risk level，and the project risk level is in a “lower” risk level.But the potentiality of mineral resources，the engineering geological conditions and the infrastructure are in a “high” risk level，which are the main project risk sources.General recommendations are as follows.Before transnational mining M&A，enterprises should do their due diligence and collect detailed data as much as possible.Decision criteria is as fallow：If the evaluation result is in a “high” risk level or above，it should be carefully decided or even directly rejected； If the evaluation result is in a “general” risk level or below，it should be treated differently，that is，carefully analyze the grade Ⅱ indexes and pay particular attention to some extreme indexes which may bring forward risks，and then estimate their possibility and scopes from the view of evading or reducing risks in the future，and then make further decisions.Corresponding risk control strategies should be made after the M&A and should also be adjusted while implementation so that the operational risks can be reduced and a good success rate can be got.
As a strategic pillar industry in China，rare earth industry plays an important role.Rare earth has been widely used in new energy，energy conservation，environmental protection，electronic information and other emerging fields，and is known as the treasure house of new materials in the 21st century and the vitamin of modern industry.The prominent negative externalities in China’s rare earth industry has a long history during the development and utilization of rare earth resource.The negative externalities mainly include short and narrow industrial chain，insufficient research and development technology of high value-added products，and ecological and environmental damage caused by resource development，which seriously restricts the safe and healthy development of China’s rare earth industrial chain.This paper focuses on the impact of the negative externality of ecological environment caused by the development of rare earth on the safety of China’s rare earth industry chain，analyzing the security threats in China’s rare earth industry chain，such as uneven development of upstream and downstream enterprises，the existing mining area governance exist hidden dangers.Therefore，putting forward to construct the vertical feedback mechanism of the rare earth industry chain security.That is，the negative external sharing behavior of the upstream and downstream enterprises in the industrial chain of rare earth.And the feedback process，the feedback stage，the negative externalities measurement and the standard of feedback were discussed.The influence of negative externalities in rare earth industry chain security is solved internalization，so it will not involve or less involve industries other than rare earth.Finally，from the three aspects of capital，technique and talent feedback，the countermeasure and the suggestion of feedback control was put forward，suggest that the government should plays a guiding role through the guidance of policy rather than a leading role in the rare earth industry chain feedback mechanism.And upstream and downstream rare earth enterprises should reduce reliance on the government governance.Solving the internalization of negative externalities affecting the safety of rare earth industry chain and involving little or no factors other than the rare earth industry chain，give play to the role of rare earth coordination between upstream and downstream enterprises feedback.In a certain extent，Feedback mechanism can mobilize the enthusiasm of rare earth associated upstream and downstream industry management of ecological environment destruction and motility.Through the establishment of the vertical feedback mechanism of the rare earth industry chain，a new governance path to offset the positive and negative externalities is sought to provide reference for the safe and healthy development of China’s rare earth industry chain.
Dabaoshan polymetallic mine has a complex environment and high requirements for ore blending.Underground mining was used early.In the later stage，in order to improve mining efficiency and reduce safety hazards，open-pit mining was used.However，this led to the legacy of more untreated mined areas,and bring a big challenge to production work.Hongda Blasting Co.，Ltd. takes the Dabaoshan Project Department as its pilot unit and fully considers its role as a mine construction enterprise in the construction of digital mines.From the perspective of practicability and investment costs，digital mines suitable for mining construction enterprises was conducted.Based on the application of various advanced mining software，adhered to the actual needs of mine construction，the UAV aerial survey，DIMINE software and truck dispatching system were used as technical support，from the data acquisition，processing and application of open-pit mine,a digital mine construction framework that could be applied in various construction management stages was constructed.Firstly，the detailed terrain and 3D models of topography were obtained by the UAV aerial survey technology.The production status and the distribution of hazard sources were clearly understood，and the macroscopic survey of open-pit mine was realized.Then DIMINE software was used in the whole life cycle of open-pit mine for production planning，daily technical submission，engineering quantity settlement and blasting automation design，which realized the three-dimensional production planning and design of mines，ensuring the scientific exploitation of resources and reduced the depletion and loss of ore.At the same time，the truck dispatching system was used to carry out the mining and real-time dispatching management，which ensured the orderly mining construction and the effective execution of the mining instructions，so as to avoid the enforced idleness due to poor organization of work.The combination of UAV aerial survey，DIMINE software and truck dispatching system has realized the organic unification of mine status investigation，safety hazard identification，production planning and design，scientific mining，real-time supervision，etc.，ensuring safe production of the Dabaoshan open-pit mine.Practice showed that compared with traditional mine construction enterprises，Hongda’s digital mine pilot work has better realized mine integrated design and integration services in mining planning and design，construction and dispatching，and on-site supervision，which has significantly improved the refined construction the management level，it could provide a certain reference for the construction of digital mines in mining construction enterprises.
Non-coal mines are prone to fire accidents due to the fragility of the mine system and the high temperature of the mine.It is important to improve the fire contingency professional skills of mine operators through contingency training, which plays an important role in the prevention and control of mine fire accidents.However, the traditional contingency training has the disadvantages of single form, poor training effect and difficulty in realizing some training contents, so this paper developed a non-coal mine fire contingency training system with comprehensive functions and strong interaction using virtual reality technology.A mine fire contingency training system functional framework consisted of four basic subsystems,namely project introduction subsystems，accident scene experience subsystems,personnel role experience subsystems and comprehensive assessment subsystems is designed.And a mine fire training system is constructed whose functions include the virtual roaming before the fire, the scene experience when the fire occurred, the evacuation,contingency rescue,post-disaster treatment after the fire,and comprehensive assessment and evaluation after learning and training.3Ds Max 3D modeling software and Unity3D game engine are utilized to establish a virtual scene of mine fire，and the C# language script programming and HTC VIVE head-mounted display device are applied to realize the interaction between trainee and the mine fire virtual scene thus the system is developed, and conducting indoor test and field test for evaluation on the system effect. The results of the indoor test evaluation show that the user experience indicators of the VR training system are generally 2 to 4 times of the PPT training，and its immersion indicator is 22.5 times of the PPT training. The training effect indicators are generally 1 to 2 times of the PPT training, and 90% of the tested students prefer the mine fire emergency training system based on VR technology.While the field test process equipment is stable, mine operators have a strong interest in the VR training system and stronger willingness to learn actively, and most of them mentioned that they can be proficient in operation system and understand the training content of the system easily.It shows that the mine fire contingency training system based on VR technology can bring better user experience and training effect, improve the efficiency of mine fire contingency training effectively, and is more popular than traditional training.The VR training system has the characteristics of low cost, easy acceptance and flexible training methods, which can achieve good training results and strengthen the fire emergency professional skills of mine operators.
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