In order to study the uniqueness of the displacement back analysis of isotropic viscoelastic rock mass, an analytical solution for the radial displacement of a circular roadway in a transversely isotropic viscoelastic rock mass was derived from the principle of elastic and viscoelastic correspondence principle. The uniqueness of the back analysis of displacement in transverse isotropic rock mass was studied according to the identifiable conditions of parameters. The results show that only knowing the displacement of the measuring point can not uniquely invert all the parameters. It is possible to uniquely invert other rock mass mechanical parameters only when at least 3 parameters are known in advance. The values of the vertical ground stress and the transverse ground stress have a significant influence on the identification of back analysis. The fewer the parameters to be solved, the more recognizable the parameters are. The initial ground stress parameters have the best identifiability, followed by Poisson's ratio, modulus of elasticity and viscosity coefficient on the isotropic surface, and the modulus of elasticity and viscosity coefficient normal to the isotropic surface are the worst. The research results provide a theoretical basis for the back analysis calculation of rock mass parameters.

In order to solve the problem of slow settling of iron tailings in a concentrator in Benxi, the appropriate flocculant was selected through the flocculant optimization test. The effects of slurry mass concentration, flocculant unit consumption and slurry pH on flocculant settling were investigated by single factor test. The microstructure of the settling process was observed microscopically, and the settling law of iron tailings was summarized. The results show that the natural settling basically ends at 600 min, and the sediments after reaching the critical point of settling will undergo the main consolidation stage and the secondary consolidation stage. The main consolidation stage ends at 2 000 min, and the secondary consolidation stage ends at 3 500 min. The height of the clarification layer remains stable immediately. The flocculation effect is the best when the flocculant is anionic polyacrylamide (APAM), slurry mass concentration is 15%, flocculant unit consumption is 20g/t, and slurry pH=9. Under this condition, the solid content of 10 min is 233.13 mg/L, and the settling rate of 10 min is 67.15%.

In order to reduce the adverse effects of loading dust on the occupational health of workers in low-concave open-pit mines and formulate effective dust reduction measures, based on the theory of gas-solid two-phase flow, the Euler-Lagrange model and Fluent numerical simulation software were used to explore the influence of different wind speeds on the diffusion and mass concentration distribution of loading dust near the side slope of low-concave open-pit mines. The results show that the flow separation occurs after the airflow passes through the steps, forming a low-speed turbulent zone, a counterclockwise structural vortex and a clockwise small vortex in the carriage, which makes the flow field structure near the －12 m horizontal mining working face and the carriage of the open-pit mines very complicated. With the increase of wind speed, the aggregation time of loading dust in the carriage is shortened, the diffusion rate of loading dust is increased, the distance of diffusion pollution effect along the X-axis is increased, and the maximum dust mass concentration aggregated in the structural vortex is significantly reduced. The dust mass concentration in the carriage is higher than 100 mg/m³, and the dust mass concentration at the height of the respiratory zone decreases along the way, and the decrease of dust mass concentration is reduced. According to the numerical simulation results and the occupational exposure limit of 8 mg/m³, the area of the dust pollution is determined to be within 15 m in front of the front of the car. Measures are formulated such as using fog gun trucks, sprinkler trucks and equipping protective equipment, and good dust removal effect is obtained.

Aiming at the dust diffusion phenomenon in the process of grab unloading, the dust-isolation with air curtain and negative pressure suction technology were combined, and the CFD-DEM two-way coupling simulation method was used to study the comprehensive dust suppression system of dust-isolation surrounded by air curtain and negative pressure suction. Through the performance simulation study of the dust-isolation surrounded by air curtain, it is concluded that the effective block of dust can be achieved when the jet velocity of the air curtain is greater than 8 m/s. At the same time, based on the theory of negative pressure suction, the relationship between the mass flow of air flow of the suction port and the unloading time was deduced by CFD fluid mechanics method, and the simulation model of grab unloading was established. The flow field distribution of the unloading plane and the mass flow rate of dusty air flow escaping from the dust-isolation hopper mouth plane were extracted by simulation to reflect the movement of the dusty air flow inside the hopper. The movement law and dust suppression effect of unloading dust before and after the installation of air curtain and negative pressure suction device were compared and analyzed through tsets. The results show that compared with traditional grab, the instullation of air curtain and negative pressure suction device reduced the maximum mass concentration of dust at the hopper mouth by 738.3 mg/m³, which is reduced by about 95.3%, and the complete settlement time of dust is shortened by 60%. The results provide a reference for efficiently solving the problem of dust diffusion in unloading.

At present, the traditional total ventilation control method on the fully mechanized heading face fails to realize dynamic control of dust reduction, and the ventilation environment in the area of personnel activity is not considered in the dust reduction process, resulting in dust accumulation. Therefore, a finite element calculation model was established for the coupling of air flow and dust gas-solid, and underground verification was conducted. According to the dust migration and distribution law and the activity range of underground personnel, different areas of personnel activity were divided. The dust mass concentration sample data under different airflow intelligent control schemes were obtained by simulation, and the data were discretized by K-means algorithm. Based on the immune genetic algorithm, the dust reduction scheme was used as the antibody, and the dust mass concentration in different areas of personnel activity was used as the antigen. The acquisition algorithm of the intelligent control of air flow and dust reduction scheme for the different areas of personnel activity were compiled. Taking a mine in northern Shaanxi Province as the research object, the optimal dust reduction scheme for the personnel in the dust accumulation area (in the range of 5−15 m) is 1.2 m outlet aperture, 5° horizontal deflection, and 5 m from the head. The dust reduction effect of the scheme was tested and verified. The result show that, after the application on the experimental platform, the average dust mass concentration in dust accumulation area is reduced from 163.77 mg/m³ to 91.32 mg/m³, which is reduced by 44.24%; the dust concentration at the driver's position is reduced from 161.94 mg/m³ to 78.90 mg/m³, which is reduced by 51.28%. After the application in underground, the average dust mass concentration in dust accumulation area is reduced from 182.81 mg/m³ to 113.94 mg/m³, which is reduced by 37.67%; the dust mass concentration at the driver's position is reduced from 179.65 mg/m³ to 101.27 mg/m³, which is reduced by 43.63%.

To improve the problem of poor soil nutrients and limited carbon sequestration capacity in the arid mining area of Northwest China, combined with field experiment and static box method, multi-source solid waste (coal gangue and sludge compost) combined with carbonate-mineralization microbe were used to improve sandy degraded soil in coal mining subsidence area. The results show that the addition of multi-source solid waste and carbonate-mineralization microbe promote the growth of alfalfa and the development of its roots, and increase the carbon and nitrogen content of alfalfa. Multi-source solid waste combined with carbonate-mineralization microbe significantly increases soil carbon and nitrogen content and soil microbial carbon and nitrogen metabolism related enzyme activities, and the improvement effect of multi-source solid waste combined with carbonate-mineralization microbe is better than that of single application of bacteria. After the addition of solid waste and carbonate-mineralization microbe, the net ecosystem exchange rate (NEE) of sandy soil decreases, and the gross primary productivity (GPP) of the ecosystem increases. The structural equation model shows that the addition of multi-source solid waste and carbonate-mineralization microbe is an important factor affecting GPP. Therefore, multi-source solid waste combined with carbonate-mineralization microbe has the application potential of improving quality and efficiency, carbon sequestration and emission reduction in soil remediation in arid mining areas in Northwest China.

Regarding the problem of collecting the impact frequency of open-pit down-the-hole drill rigs, based on the characteristics of the drilling acoustic signals of the TAIYE-390-Ⅱ split hydraulic open-pit down-the-hole drill rig, the impact frequency acquisition system and acquisition method were analyzed. Under the condition of constant wind pressure and constant axial pressure, drilling acoustic experiment and blasthole peep experiment were carried out to study the stability of the system and the feasibility of impact frequency in the identification of rock mass structural plane. The results show that 6 kHz is the most obvious signal dominant sampling frequency of the impact section waveform. The impact frequency acquisition method of acoustic signal in drilling process based on Hilbert transform, variational mode decomposition (VMD) and Savitzky-Golay filter can accurately extract the real-time impact frequency of drilling, and the error is controlled at 1 Hz. The impact frequency has a relatively obvious response to the rock mass structure. When encountering various structural planes, the value of the impact frequency will decrease by 1−3 Hz. The research results have important theoretical significance and application value in aspects such as the collection of the impact frequency of down-the-hole drills and the identification of rock mass structural planes.

In order to improve the magnetic field performance of the flat magnetic separator and reduce its manufacturing costs, the finite element method, response surface method, and Nondominated Sorting Genetic Algorithm Ⅱ (NSGA- Ⅱ) were used to perform multi-objective optimization analysis on the structural parameters of the planar extrusion magnetic system. Firstly, a response surface analysis experiment was conducted using the structural parameters of the extrusion magnetic system as variables. The response values of the area field intensity and magnet efficiency density were calculated through numerical simulation, and a regression model of the objective function was constructed. The fitting accuracy of each regression model was evaluated using analysis of variance. Then, a multi-objective optimization model was constructed with the objectives of area field intensity, magnet efficiency density, and number of magnetic poles, and a Pareto solution set was calculated to obtain a series of optimization schemes. The research results indicate that the regression model of area field intensity and magnet efficiency density has a high fitting accuracy and a good predictive ability. The Pareto solution set reveals a conflicting relationship between the area field intensity with the efficiency density and number of magnetic poles of the magnet. The error range between the multi-objective optimization model with the simulation results is 0.73%−5.30%, which verifies the reliability of the multi-objective genetic algorithm in optimizing the design parameters of the planar extrusion magnetic system.

Las Bambas is a high-altitude mine with remote geographical location and harsh environment. Based on the core requirements of Las Bambas Mine towards intelligent mine and many problems of unfavorable directly deploying a large number of personnel to participate in mine operation on site, all the functional support on the Las Bambas Mine operation value chain was analyzed, the existing intelligent system was reviewed and optimized, the digital operation center (DOC) of Las Bambas Mine was established, and its implementation effect was summarized and analyzed. The results show that the establishment of mine digital operation center improves the digitization, automation and intelligence level of mine operation, simplifies the approval process of staff, and realizes 100% remote integrated operation. The digital operation center realizes the safety integrated management of personnel, equipment and environment, the efficiency is 97.7%, the accuracy of fatigue prediction is 94.7%, and the number of heavy trucks hitting the primary crusher structure is reduced by 90%. The role changes of 20 positions in mine production involve the on-site migration of 63 employees, which realizes the remote processing of process integration and on-site process scheduling. The research results can provide reference for mines in the same type of high-altitude and remote areas in terms of personnel reduction, remote office scheduling and digital operation.

In response to the characteristics of a tungsten-molybdenum-bismuth polymetallic mine in Hunan Province, which contains magnetic iron, low and fluctuating molybdenum grade, and high content of mudstone gangue, an experimental research was conducted to optimize the beneficiation process and reagent system in order to improve the beneficiation recovery rate of molybdenum. The research results show that adopting the process of "magnetic separation followed by flotation—molybdenum-bismuth iso-floatability flotation—bulk flotation of residual sulfide ore", good mineral processing indicators can be achieved by taking CD-N as the regulator, B-8 combined with butyl xanthate as the sulfide ore collector, and F6 as the frother. The molybdenum closed circuit test obtained a molybdenum-bismuth mixed concentrate with Mo grade of 3.46%, Bi grade of 2.03%, Mo recovery rate of 85.40%, and Bi recovery rate of 80.05%. Compared with the on-site production conditions, the recovery rate of molybdenum is increased by nearly 5 percentage points, achieving efficient recovery of molybdenum. The new reagent system doesn't affect the subsequent scheelite flotation, providing a technical basis for the subsequent expansion and renovation of beneficiation plant in the tungsten-molybdenum polymetallic mine.