Songshudaban gold deposit in Yanqi County is located in the middle part of the Southwest Tianshan of Xinjiang gold polymetallic metallogenic belt，and near north margin of suture zone between the Tarim plate and Kazakhstan-Erie plate.Songshudaban gold deposit produced in the Sahentuohai-Dashankou brittle-ductile shear zones.The ore-bearing rock are a set of fine clastic rocks and quartz veins from the middle Devonian Saaerming formation.The NW and NWW trending faults developed in the mining area，and metallogenic geological conditions are superior.1∶10 000 geological survey，1∶10 000 soil geochemical survey and explora-tory trench reveal，and other works have been carried out in the area.Four gold orebodies were found，but these orebodies have the features of small scale，low grade and extends unsteadily，the prospecting results are not outstanding.To identify abnormal sources of soil geochemical anomalies and search mineralized rich areas of gold，expand the size of the existing gold orebodies or find new gold orebodies in Songshudaban area，the 1∶2 000 rock geochemistry profile measurement were carried out，two primary halo comprehensive anomaly zones of Au，As，Sb，Hg，Cu，Bi with NWW trending were delinead.The anomalies are mainly distributed in limonite mineralized，kaolinized sericite phylliterelated to ductile shear zone.The mineralization and alteration of sericite chlorite slate，andesite porphyry，marble and other strata on both sides of the shear zone is relatively weak.After anomaly verification，three new gold orebodies and mineralization spots were found.The engineering control gold orebodies are 60~120 m long and 1.00~3.25 m thick with a grade of 0.65×10-6~2.85×10-6，it means that the good geochemical anomalies and ore prospecting results have been achieved.According to the features of rock geochemistry and gold mineralization，it is believed that the first subgroup of middle Devonian Saaerming formation is the favorable strata for searching gold deposits，and it is very important ore-searching criteria.The gold deposit is strictly controlled by ductile shear zones.There is great potential to find ductile shear zone gold deposits in Songshudaban mine area.
Minxian-Lixian metallogenic belt is rich in polymetallic resources in the west Qinling area，which has a complex tectonic history.However，there is still a lack of research on the geochemical anomaly patterns and ore-controlling factors of different types of deposits，which restricting the deployment of ore prospecting and exploration.To solve the problems，data of stream sediment geochemistry is utilized to study metallogenesis at a regional scale，to reveal the characteristics of distribution and association of geochemical elements，and thus provide important guidance for prospecting and exploration.A total of 4 095 samples were collected in the area and centered log-ratio（CLR） transformation was performed in the following to alleviate the skewness of raw data and make the element concentration tend to a normal distribution.Based on the fractal theory，Concentration-Area （C-A） models of Au，Cu，Pb，Zn，W and Sn have been established.It is found that elements of Au and Sn have multiple levels of geochemical fields，indicating that they have higher degree of enrichment and metallogenic potential.The geochemical anomalies of Au，Cu，Pb and Zn in the north subbelt can be roughly divided into two categories.One is related to the Late Triassic intrusive magmatism，where Suolong and Mawu gold deposit and Daijiazhuang Pb-Zn deposit expose.Another is related to the regional complex fault-fold system （Minxian-Tanchang fault and the Diebu anticline），where Zhaishang super-large gold deposit and several mineralization points expose.Also，anomalies of W and Sn show a strong spatial correlation with the Wuduojinhua pluton，hosting many mineralization points.Before performing factor analysis， Bartlett test of sphericity and KMO test were used to test the relevance of the selected data.The results show that the KMO value is 0.91，and Bartlett’s sphericity test also meets the conditions of factor analysis.The results of factor analysis indicate：（1）The element association of the first factor （F1） is Co-Cr-Cu-Ni-Ti-V-Zn，which represents the Late Paleozoic strata，and the factor score is consistent with the regional Cu，Zn mineralization，indicative of mineral sources from the strata.（2）The second factor （F2：As-Hg-Sb） represents the association of cryogenic elements，controlled by the Minxian-Tanchang fault and the Diebu anticline.（3）The third factor （F3：Bi-Sn-W） represents the element association of high temperature，controlled by Wuduojinhua pluton and the Diebu anticline.（4）The fourth factor （F4：Ba-Pb） shows similar patterns as F3；（5）The fifth factor （F5） has a single element of Au and it is irrelevant with the known Late Triassic magmatism，which indicates that the Au mineralization probably is related with complex tectonic system instead of magmatism.The main conclusions include：（1）C-A fractal model shows that elements of Au and Sn have higher degree of enrichment and metallogenic potential.（2）The results of factor analysis show that Cu and Zn mineralization probably come from the Late Paleozoic strata，Pb-Zn and W-Sn mineralization is related to magmatism of the late Triassic.The tectonic ore-controlling effect on Zhaishang gold deposit is more obvious.（3）Based on the combination of C-A fractal model and factor analysis，it is predicted that the Diebu anticline has a huge prospecting potential of Pb-Zn and W-Sn.
In order to solve the deep prospecting problem of Jidongwan mining area in Luocheng County，Guangxi，the geo-electrochemical extraction method was carried out to explore concealed tin-copper polymetallic deposits.It is found that the geo-electrochemical extraction anomaly，shown above the known orebody profile，exists a high correspondence with the orebody，which can better reflect the concealed tin-copper orebody.It means that the geo-electrochemical extraction method is feasible to find tin-copper polymetallic deposits in the Jidongwan mining area，and it has good effectiveness and adaptability. The factor analysis of the geo-electrochemical extraction element data in the study area was conducted.The results show that the elements can be classified into four elemental assemblages，namely，F1（Cu-Ni-Co-Pb-Zn），F2（Ag-Bi），F3（W-Sn） and F4（B）.According to the spatial distribution pattern of single elements and elemental assemblages anomalies extracted by the geo-electrochemical approach，it can be seen that each element has a high anomalous definition，intensity，and good continuity.Besides，the elemental assemblages are anomalously well-nested and clearly zoned.Based on the analysis of the spatial distribution characteristics of the geoelectric extraction elements and the combined element anomalies in the Jidongwan mining area，according to the size，intensity，morphological characteristics and the degree of agreement between the anomalies，combined with the geological location and geological characteristics and other factors， two A type target areas（A-1，A-2） and two B type target areas（B-1，B-2）are delineated in the study area.It is believed that the study area has favorable ore-forming geological conditions，which is a favorable location for searching for concealed tin-copper polymetallic orebodies，and has great prospecting potential.
Based on the dual functions of commodity and currency，this paper takes the great influence of gold price fluctuation on the world economy.At present，most of the literatures analyze the influencing factors of international gold futures price fluctuation from three aspects of supply and demand，finance and index.However，due to the instability of the global political and economic environment，international gold futures prices fluctuate violently.Few scholars consider the impact of geopolitical risks and economic policy uncertainty on the price fluctuations of international gold futures.At the same time，few scholars combine the above two factors with other variables to analyze the influencing factors of international gold futures price.In order to better explore the main influencing factors of international gold futures price，this paper used the monthly price data of international gold futures from 2000 to 2019，using VAR model，VECM model，cointegration test，impulse response and variance decomposition to conduct empirical research.At the same time，Granger causality test was used to analyze the causal relationship between the variables and the international gold futures price.The analysis focuses on the results of impulse response，which is different from the method of orthogonal impulse response in traditional dynamic analysis.In this paper，the generalized impulse response analysis method was used.The results show that there is a long-term equilibrium relationship between international gold futures price and geopolitical risk，economic policy uncertainty，dollar index，interest rate level，U.S. inflation level and the D-value between global gold supply and demand，and dollar index have the most significant impact on international gold futures price.Geopolitical risks and economic policy uncertainties have a positive impact on the international gold futures price in the short term，while the positive impact of economic policy uncertainties is longer.This paper provides a better theoretical basis for predicting the trend of gold price.
Deep mining has gradually become a new trend in underground mining，and the non-explosive mechanized mining method，as one of the alternatives to conventional drilling and blasting excavation，has shown great advantages in rock-breaking efficiency and safety.Non-explosive mechanized mining of hard rock mines is a technical problem that needs to be solved to realize continuous mining and safe，efficient and green development of deep resources in hard rock mines.In the roadway excavation，the initial stress state of the surrounding rock is destroyed to form a secondary stress field resulting in the phenomenon of stress concentration，which will form a “crushing zone” around the surrounding rock，called the excavation damage zone （EDZ）.The feasibility of non-explosive mechanized mining is closely related to the thickness of the EDZ around the ore to be cut.The existing research shows that the thickness of the EDZ is mainly affected by rock properties，ground stress，geological conditions and excavation parameters and other factors.So in this paper，the characteristics of the EDZ thickness were considered comprehensively，and five influencing factors of uniaxial compression strength，rock mass grade，burial depth，rock bulk and excavation span were selected.Through multiple regression analysis，using 69 sets of data collected at multiple mine sites，a functional relationship between the thickness of the EDZ and five influencing factors was established，so as to obtain the prediction model of the thickness of the EDZ.The results were obtained by comparing the measured data of the EDZ thickness with the prediction values obtained from the EDZ thickness prediction model.The high determination coefficient and the low root mean squared error show that the established EDZ thickness prediction model and the non-explosive mechanized mining criterion have good reliability.In addition，the weights of the five influencing factors on the thickness of the EDZ were evaluated by the entropy weight method and ranked in order.The results show that the uniaxial compressive strength has the largest influence on the thickness of the EDZ，the rock mass grade has the smallest influence on the thickness of the EDZ，and the burial depth，rock bulk density，and excavation span have increasing influence on the thickness of the EDZ.The regression prediction model can better predict the thickness of the EDZ at Kailin Maluping mine，and the predicted value meets the requirements of non-explosive mechanized mining，verifying the feasibility and rationality of non-explosive mechanized mining.
The Xiling mining area in Sanshandao gold mine is the first coastal metal mining area in China.Therefore，it is of great significance for coastal rock engineering excavation design and disaster control to study the effect of the buried depth on in-situ stress，rock mechanical properties and their relationship.For this purpose，the standard rock specimen at 5 different buried depths ranging from 300 m to 1 900 m were taken from the three geological drilling in this mining area，namely ZK88-21，ZK88-14 and ZK94-2.With the aid of MTS815，the mechanical parameters and acoustic emission Kaiser point in different directions of rock at different buried depths were tested，and the mechanical properties and in-situ stress of rocks were further obtained.On this basis，the in-situ stress，rock mechanics parameters and their interrelationships at different buried depths were analyzed.The results show that the mechanics parameters，self-weight stress，vertical stress，maximum horizontal stress and minimum horizontal stress have a logarithmic relationship with the buried depth，and the increase amplitude of vertical stress is gradually smaller than that of the self-weight stress with the increase of the buried depth.Similarly，the rock mechanics parameters are roughly logarithmic to the in-situ stress.Among them，the effect of the maximum horizontal stress on the rock mechanical parameters is greater than that of the minimum principal stress.In addition，the effect of buried depth on the tensile strength is greater than its effect on the compressive strength.
Under certain conditions，such as the drilling surrounding rock cooled by drilling fluid in geothermal development，the surrounding rock rapid cooled in the process of extinguishing the fire，rock in rock mass engineering will experience rapid temperature change（thermal shock）.Therefore the study of thermal shock in rocks is of great significance for stability analysis of rock structure affected by thermal shock.Granite specimens were heated to the high temperatures of 200 ℃，400 ℃ and 600 ℃，and then cooled by three methods of water cooling，air cooling and cooling in the stove.The physical properties such as dry density，P-wave velocity，porosity of granite after distinctive thermal shock were measured.The dry density and porosity were measured with buoyancy techniques.The P-wave velocity was measured by a non-destructive ultrasonic detector.As the heating level and cooling rate rise，the dry density and P-wave velocity present a descending trend，and the porosity presents an ascending trend.The damage degree of granite increases with the increase of heating temperature and cooling rate.The dynamic tensile tests were performed on the specimens after distinctive thermal shock treatment utilizing the split Hopkinson pressure bar system.The dynamic tensile strength of granite heated at 600 ℃ is less than that of granite heated at 400 ℃ and 200 ℃，and the dynamic tensile strength of water-cooled granite is less than that of air-cooled and stove-cooled granite.The damage degree of the granite caused by thermal shock was analyzed by the crack morphology of the specimens recorded by high-speed photography during the tensile failure and the morphology of the broken pieces after failure.The results show that the damage degree of granite increases with the increase of heating level and cooling rate.Scanning electron microscopy （SEM） was used to identify the microcosmic damage and fracture characteristics of granite caused by thermal shock.There are two kinds of characteristic fracture morphology of thermal shock were observed on the specimens after heated at 400 ℃ and 600 ℃ （both air-cooled and water-cooled conditions）.However，neither fracture morphology can be found at 200 ℃ （including 3 kinds of cooling conditions）.Therefore，there is no thermal shock at 200 ℃；When the heating level reaches 400 ℃，the granite is damaged by high temperature and thermal shock.When the heating level reaches 600 ℃，the granite is badly damaged.And the damage degree of granite increases with the increase of heating temperature and cooling rate.This study can provide theoretical basis for the analysis of thermal shock damage and the evaluation of rock mass stability after high temperature disaster in practical engineering.
With the increasing emphasis on mine safety exploitation and the environment protection，filling mining method has been widely applied in many underground mines around the world.The damage and strength criterion of backfill is the most basic research content of filling mining and the research on the damage and strength of backfill is the most basic research content of backfill material.Thus，it is of great significance to the underground engineering to determine the mechanical properties and damage characteristics of backfill materials.In oder to reveal the damage mechanism of backfill material under uniaxial loading，firstly，the five successive stages of the stress-strain curves of backfill material under uniaxial loading were analyzed，such as initial compaction stage（OA），elastic deformation stage（AB），strain hardening stage（BC），strain softening stage （CD） and residual strength stage（DE），then taking the damage variable as the internal variable that affecting the mechanical properties of backfill materials，and the classical damage constitutive model of backfill material under uniaxial loading was derived based on the statistical damage theory，maximum-tensile strain yield criterion and strain equivalent hypothesis.Due to the backfill material contains a large number of micro defects such as micro pores and micro cracks，and there is a compaction process of the backfill specimen in the initial loading stage，a compaction hardening coefficient was proposed and introduced to the classical damage constitutive model and the modified damage constitutive model was established，which makes up the defects that the classical damage constitutive model cannot explain the compaction process of backfill in initial compression stage.The modified damage constitutive model was used to fit a variety of experimental data and was compared with the fitted results of the classical damage constitutive model.The results show that the modified damage constitutive model can not only simulate the compaction process of the backfill specimen in the initial loading process，but also be consistent with the stress-strain experimental data，and the fitting results are much better than those of the classical damage constitutive model，which fully indicates the feasibility of the modified damage constitutive model.The influence of the change of fitting parameters on the shape of the fitting curves was also studied and the control variable method was used to change one of the parameters to study the change trend of the shape of the fitting curves.The results of this study show that three different types of fitting parameters have different effects on the shape of the fitting curves.
The downward layered approach cemented filling mining method was selected in Jinchuan nickel deposit，but there is a problem of high filling cost and low production capacity.In order to reduce the cost of filling mining，the industrial filling test of waste rock and tailing mixed aggregate was carried out based on a large number of laboratory studies.Firstly，the particle size analysis and grading study of the -16 mm waste rock coarse aggregate and dressing tailings fine aggregate were carried out.The results show that the diameters of the two kinds of aggregate belong to filling aggregate with discontinuous distribution and poor gradation.According to the different ratios of the two kinds of aggregate，the compactness test of the mixed aggregate was carried out，and the relationship curve between the ratio of waste rock tailings of the mixed aggregate and the compactness was established，so as to determine the optimal ratio of the mixed aggregate when the compactness reached the maximum.The research results show that when the ratio of -16 mm waste rock and dressing tailings is within the range of 7∶3 to 5∶5，the density of mixed aggregate accumulation reaches or approaches the maximum，and the corresponding ratio of mixed aggregate particle size is continuously graded.Then，the industrial filling test was carried out for the mixed aggregate with the ratio of waste rock and tailing of 6∶4 and 5∶5，thus obtaining the strength of the cemented backfill with the mixed aggregate of the two ratios.The test results show that when the cement content is 260 kg/m3，the strength of cemented backfill of the two kinds of mixed aggregate meets the strength requirements of cemented backfill in the downward layered approach and cemented filling mining method in Jinchuan mine，and the strength of the mixed aggregate cementing backfill in the ratio of 6∶4 is higher than that of the mixed aggregate cementing backfill in the ratio of 5∶5.According to the observation on the fracture surface of the cementing backfill test block，when a single stage of mixing is used，there are uneven mixing of the mixed aggregate filler slurry and agglomeration of cement and tailings，resulting in poor homogeneity of the cemented filler and low overall stability.So for the waste rock-tailing mixed aggregate filling slurry，it is recommended to use two-stage activated stirring，which can not only improve the overall quality of the filling body，but also improve the fluidity of the filling slurry，which is conducive to the pipeline self-flow transportation of the filling slurry.It is also found in the industrial filling test that the precise ratio of slurry of mixed aggrgate is another important factor affecting the quality of cemented backfill and slurry pipe transport characteristics.Therefore，improving the ratio of waste tailing aggregate and adding amount of cement and water is an important factor to realize the safe and reliable application of waste tailing mixed aggregate in filling mining.
Paishanlou gold mine uses crushed stone and cement slurry spray cementation filling technology，and the cement consumption accounts for more than 15%.Due to the poor water absorption of the crushed stone，the gaps between the particles are large and interconnected，a considerable part of the cement slurry is lost，which not only causes waste of materials，but also seriously pollutes the underground environment.In order to solve the problem of the lack of filling materials，the Paishanlou gold mine investigated the conditions of the source of aggregates near the gold mine.Then construction waste piled up on the southern edge of Fuxin City was processed and crushed into underground paste filling material aggregates.Portland cement was used as a cementing material，and a scientific and reasonable material ratio was designed to fill the goaf.By using construction waste，while solving the problem of insufficient sources of underground filling materials，it reduces various hazards caused by a large amount of construction waste.Not only can it bring significant economic benefits to the enterprise，but also make full use of bulk solid waste，resulting in huge environmental and social benefits.Using the method of geotechnical test，the universal hardness of the concrete block was measured to be 3.74，which is a medium firm rock，and the difficulty of breaking is moderately small.The universal hardness of the brick is 1.17，which is a relatively soft rock and easy to break.The apparent density of the material is 2.137，which is less than 2.6~2.8 of general rocks.The natural moisture content is 3.56% and it is in a relatively dry state.The water absorption rate is 9.3%.In view of the lack of intermediate particle size of construction waste in primary crushing，a new crushing process was proposed：1/3 of the coarse aggregate after primary crushing is crushed to less than 15 mm and backmixed to obtain a well-graded aggregate.Good gradation is beneficial to the workability，water requirement and fluidity of the slurry.Aiming at the strength and fluidity of paste filling materials，construction waste is used to prepare aggregates，ordinary cement is used as cementing material，and fly ash is used as additives to prepare paste materials that meet fluidity and strength requirements.Uniaxial compressive strength tests and slurry slump test were conducted.The results show that when preparing aggregates from construction waste， 15% fly ash，10% cement，and 78% slurry mass concentration are the optimal mix ratios.The uniaxial compressive strength of the filling body is 1.15 MPa at 3 d and 3.5 MPa at 28 d.The moisture content is 27%~28%， and the slump is 21.5 cm to 24.0 cm.It can meet the requirements of the strength and fluidity of the paste material.
The application of power plant ash to mine goaf filling can enrich aggregate source and consume a large amount of solid waste，which has important social benefits.Power plant ash mainly refers to the ash produced by coal-fired power generation，which is a kind of bulk solid waste with the characteristics of large discharge and low utilization rate.The properties of ash produced by different types of power plants are very different，but they generally have certain pozzolanic activity and gelation characteristics，so they are good filling materials.In order to explore the influence of different ash residues on the strength of the filling body，fluidized bed bottom slag，fluidized bed fly ash and fly ash were mixed with different ratios as filling aggregate，ordinary silicate cement was used as cementation material，and add water to prepare paste material，then fluidity test and compressive strength test were carried out.The results show that：（1）The fluidized bed ash contains some cementation components，the fly ash has the water-reduction effect and the pozzolanic activity，both of which are good downhole filling materials.（2）When the moisture content of paste material exceeds its critical moisture content，the fluidity will be greatly improved，which will also lead to segregation and dehydration of the filling material，then reduce the strength of the filling body.（3） When the ratio of fluidized bed bottom slag，fluidized bed fly ash and fly ash is 6∶2∶1，cement content is 10%，the slurry concentration is 73%，the slump is 20 cm，and the 28 d strength of the filling body can reach 3.3 MPa.This ratio not only meets the requirements of slurry fluidity and backfill strength，but also greatly reduces the filling cost.（4）Taking the above ratio as the control group，the grading optimization experiment was carried out.The undisturbed bottom slag was broken，then the fine particles with different particle sizes and proportions were used as fine aggregate to replace the undisturbed bottom slag.When the particle size of the broken bottom slag less than or equal to 5 mm and the replacement rate is 10%~15%，the strength of filling body reaches 2.4 MPa on 7 day and 3.5 MPa on 28 day，and the strength is significantly improved.The experimental study of the paste filling material prepared from the ash residue of power plant with a specific ratio provides data support and theoretical basis for engineering application，which is of economic value and environmental protection significance.
The development of any enterprise must take safety as the fundamental premise，and safety is the first priority of mining enterprises.Mining-related occupations have significant hazards that are difficult to eliminate and characterized by a lower occupational safety culture and a higher accident rate than occupations with lower or easily eliminated hazards.The safety production situation in metal mining enterprises is still very serious，and human-induced accidents account for most of them.Therefore，it is very important for enterprises to strengthen the construction of their own safety culture and let employees develop good safety behavior habits.The current literatures mainly focus on the relationship between safety culture and safety behavior，but few studies focus on the mediating variables between them.In order to further explore the mechanism of the effect of safety culture on employees’ safety behavior in metal mining enterprises，psychological authorization was introduced as a mediating variable.Questionnaire and empirical analysis were used in this study.A questionnaire survey was conducted among the workers in a metal mining enterprise in Guangdong，and the data were analyzed by using the structural equation modeling software SmartPLS in empirical analysis.The data collected by the questionnaire survey have good reliability and validity and can be used for further analysis.The results show that safety culture has a positive and significant effect on employees’ safety behavior，and psychological empowerment plays a complete mediating role between safety culture and safety behavior.The influence of each dimension of safety culture on safety behavior is different.The direct influence coefficients of safety communication，safety management commitment，safety training and safety incentive are 0.495，0.481，0.276 and 0.155，respectively.In the dimension of psychological empowerment，the influence path coefficients of job meaning，self-efficacy and autonomy on safe behavior are 0.200，0.180 and 0.696，respectively.The study further defined that the psychological authorization between safety culture and safety behavior plays a specific role.Therefore，the leaders of metal mining enterprises should not only strengthen the construction of safety culture to improve the safety behavior of employees，but also be good at creating a sense of psychological authorization for employees to improve their work autonomy and self-efficacy，so as to enable employees to develop good habits of safety behavior，in turn，improve employee safety behavior，to achieve the purpose of reduce and prevent accidents，truly realizing the metal mine enterprise intrinsically safe.
Underground metal mineral have the characteristics that resources condition and underground conditions are complex，with diverse mining methods.Apart from this，mine production is always in an uncertain and constantly changing dynamic process.How to obtain a scientific and effective production plan quickly has always been an urgent problem for mining enterprises.In order to solve this problem，a variety of production planning methods are used in the production process of mines，such as multi-objective programming algorithm，mixed integer programming，genetic algorithm，quantum particle swarm optimization，critical path method，and so on.The risk of uncertain in production process of mines often result in fail to complete the project on time，which will have a significant influence on the reputation and income of the mining enterprises. For the purpose of solving the problem of uncontrollable shortest construction period and high operating cost existing in traditional underground mining plan preparation，an automatic search method for the critical path of mining plan under resource constraint was proposed.Firstly，a network diagram was generated automatically according to logical relationships （subsequent operations，start time，end time and process ID） between operations，and resource constraints for the chart need to be add.Then，the current process of each stope was determined according to the information in the process sequence and the plan connection table，and assigned priority to different processes according to different resource allocation priority rules.The priority of first process in every stope was assigned according to the earliest start time of the operation and resource demand intensity，and the priority of the remaining processes was determined according to the completion time of the previous process in process sequence and resource intensity.At last，the network diagram under resource constraint needs to be updated，taking current node as an initial node，an improved depth-first search algorithm was used to traverse the directed graph，and find all mining paths in current process recursively. The path that taken the longest time was critical path，which represented the current shortest completion time of the mining plan under resource constraint.The idea of critical chain was applied to the Sanguikou mine of Zijin Mining，and the result shows that the method uses for optimizing the mining plan makes full use of the advantage of critical chain management.The method not only solves the problem of resource constraint and the shortest construction period，but also shorten the time for planning and the time for mining plan.What is more，it reduces the operation cost.During the construction period，the adjustment and optimization of the mine plan were completed，and the sustainable and efficient production of the mine was realized finally.
The slope top and bottom line plays an important role in open-pit mine mining design， production planning，calculation of stripping volume，road network planning，etc.Traditional extraction methods require the use of total stations and other equipment to rely on manual extraction，which is inefficient.In order to solve the problem of low efficiency of the traditional method of manually extracting the slope top and bottom line from the open-pit mine 3D model，a method of automatically extracting the slope top and bottom line from the open-pit mine DEM （Digital Elevation Model） 3D model was studied.The first step of the method is to pre-process the elevation data with up-sampling and bilateral filtering.The second step is to set a threshold，then according to the different elevation values of different regions in the DEM 3D model，different regions are converted into grayscale images with different pixel values.The last step is to perform gradient operation on the gray image，extract the edge pixels in the image，combine with an improved Zhang-Suen algorithm to extract the skeleton of the edge lines，and design a search algorithm based on eight neighborhoods to order the edge pixels and connect them into a complete contour line，and use the Douglas-Peucker algorithm for thinning to get the final step line.The experiment used the measured three-dimensional model data of an open-pit mine for testing.With the aid of a three-dimensional visualization software platform，the extracted step line is superimposed with the three-dimensional model of the pit，visually analyzed and compared，and the accuracy of the extracted results is judged.The visualization results show that compared with the traditional manual extraction method，the automation method greatly improves the work efficiency under the condition of ensuring the extraction accuracy，and most importantly realizes the automation of the extraction process.This method is also applicable to the terrain features of the DEM 3D model line extraction.
In order to improve the efficiency of VR training for non-coal mine roof fall，based on Unity3D，3DMax and Visual Studio 2019 software，a mine roof fall accident teaching and training platform has been developed including three modules：Pre-training，hidden rock recognition training and disaster site escape training.The platform uses 3DMax modeling software and Unity3D engine to complete the mining VR environment modeling，through the HTC VIVE equipment to complete the interaction between trainees and the mine virtual environment，using virtual coaches for demonstration teaching.Firstly，train the trainees through the mine knowledge question bank to improve the trainees’ cognition level of the mine，and then use the virtual coach to guide the trainee to identify and clear the hidden rock blocks and escape from the disaster site.The comparison of the training effect of the virtual coach and the traditional UI text was carry out，and the trainees will be tested on the disaster scene and the effect evaluation of the VR virtual coach training platform will be completed.The results showed that the average time of escape for trainees trained by virtual coach was 192.9 s，and the average time for trainees trained by UI text was 238.1 s.The latter was 45.2 s longer than the former.The test were repeated one week later. The average time of the trainees who trained by virtual coach was 224.7 s，and the average time of the trainees who used UI text training was 290.9 s.The latter was 66.2 s longer than the former.At the same time，compare to the first test，the escape time of trainees using virtual coach training increased by 16.5%，while the escape time of trainees using UI text training increased by 22.2%.The test results show that the VR technology-based non-coal mine roof fall teaching and training platform can promote the trainees to maintain a longer-term memory of the training content，and the overall training efficiency is higher than UI text teaching，which can effectively improve the trainees’ safety awareness and emergency response capabilities.Interviews with trainees show that the use of virtual coach training can better guide trainees’ attention，create an atmosphere of real-person teaching，and have good promotion and application value.
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