In the future, China will implement manned lunar landing missions, establish a permanent base on the lunar surface, and realize the exploitation and utilization of lunar mineral resources. To address the issue of determining bearing capacity of lunar soil during lunar surface construction, a method was proposed to use small-scale laboratory loading tests to deduce the allowable bearing capacity and settlement of lunar soil simulant under large-scale foundations was proposed. Firstly, plate loading tests were performed on lunar soil simulant with a compactness of 78% using circular loading plates with diameters of 6 cm, 8 cm, and 10 cm, respectively. The measured load-settlement (p-s) curves of the lunar soil simulant were obtained, and through curve fitting, the initial tangent modulus and ultimate bearing capacity were extracted. The tangent modulus method was adopted to establish the relationship between the tangent modulus of the lunar soil simulant and its initial tangent modulus, applied additional stress, as well as ultimate bearing capacity. Furthermore, based on the settlement calculation theory, the p-s curves under foundations of arbitrary sizes were calculated. Validation against the results of small-scale load tests demonstrated a good agreement between the calculated p-s curves and the measured ones. Secondly, the proposed method was employed to compute the p-s curves under large-scale foundations, and the allowable bearing capacity of large-scale foundations was comprehensively characterized by integrating the ultimate bearing capacity criterion and settlement control method. The analysis results of bearing capacity of lunar soil simulant under large-scale circular and square foundations indicates that with the increase in foundation size, the allowable bearing capacity of the lunar soil simulant under both types of loading plates increases. Additionally, the allowable bearing capacity of the lunar soil simulant under square loading plates is higher than that under circular ones of the same size. It can be inferred from the calculated p-s curves that the settlement of the lunar soil simulant corresponding to the determined allowable bearing capacity meets the engineering requirements. According to the standard size of circular loading plates used in conventional loading tests, the allowable bearing capacity of the lunar soil simulant employed in this study has been deduced to be 122 kPa. The proposed method for determining the allowable bearing capacity of lunar soil simulant provides a scientific approach and theoretical basis for the determination of lunar soil bearing capacity during the construction of lunar bases and the exploitation of lunar mineral resources.

Sediment plumes generated during the mining of polymetallic nodules have a significant impact on the seabed ecosystem. To explore the sediment resuspension and dispersion phenomena under the shear disturbance of mining vehicles, a simulation study was conducted based on a finite element analysis of Eulerian model. The plume dispersion under different roller velocities (0.1-0.9 m/s) and indentation depths (33 cm and 18 cm) was analyzed, and the effectiveness of plume shields was evaluated. Results indicate that when the roller velocity exceeds 0.3 m/s, the plume size and height significantly increase, with the maximum plume height reaching 1.4 m. As reducing the indentation depth, the average plume diffusion velocity and plume size noticeably decreases. Additionally, with the addition of a plume shield, the plume size reduces by about 51%, plume height decreases by 25%, and diffusion tendency reduces to 46%, indicating that the plume suppression devices such as shields can effectively mitigate the plume. The study can provide a reference for controlling plumes in the mining of deep-sea polymetallic nodules.

The stability of deep roadway is one of the keys and difficulties in deep mining. Taking the deep mining of a hard rock metal mine as the engineering background, according to the ground pressure stress test results, FLAC3D was used to construct the numerical model, and five representative altitudes were selected to quantitatively analyze the auxiliary ramp stability under different support schemes from four aspects of stress, displacement, strain and plastic zone. The results show that when the circular arch is supported by C30 shotcrete with a thickness of 100 mm, the auxiliary ramp can remain stable at elevations of 2 325 m or above, but it is unstable at elevations of 2 175 m and 1 950 m, so it needs to be strengthened. When the floor is laid with C30 cast concrete with a thickness of 300 mm, the floor within the elevation range of 2 850 m to 1 950 m shows unstable conditions. Three schemes of strengthening support were studied respectively: only increasing the shotcrete strength of the arc arch support body, only increasing the shotcrete support thickness, and extending the arc arch support body into a cylindrical support structure. The results indicate that none of these schemes can maintain the stability of the deep section of the auxiliary ramp. A joint support scheme of "cylindrical structure+sprayed steel fiber concrete+lagged floor building" was proposed. Calculation results has verified the feasibility of this scheme, which is recommended for the auxiliary ramp below the elevation of 2 325 m in the mine. The supporting body is cylindge-shaped CF35 sprayed steel fiber concrete with a thickness of 100 mm.

In view of the problem of high-temperature thermal hazard in the underground of Sanxin Gold-Copper Mine, a pre-cooling system was constructed based on the stratum cold storage cooling technology, utilizing the abandoned roadways in the mine's constant temperature zone for cold storage in winter and cold release in summer, which can achieve the overall cooling of underground airflow. Through theoretical calculations combined with the local geothermal conditions, a cost-effective comprehensive cooling scheme was finally formed. The Ventsim software was used to simulate and optimize the ventilation system to verify the feasibility of the selected scheme. The results show that the mine's pre-cooling line is selected as Line 1, with a ventilation resistance of 801.71 Pa, which can be matched with the K40-6No.18 fan to ensure efficient cold energy transmission. Before the optimization of the ventilation system, the temperature of the air path in the bottom level of the model in summer is 29.5 ℃, and after optimization, it drops to 25.3 ℃, with a reduction of 4.2 ℃, achieving a good cooling effect. Field application shows that after the optimization of stratum cold storage cooling, the average wet-bulb temperature of each measuring point in the deep level drops to 24.62 ℃, and the average wind speed increases to 1.27 m/s, and the temperature of the air path after cooling meets the regulatory requirement of being lower than 27 ℃.

As a transition scheme between open pit mining and underground mining, hanging wall ore mining is of great significance to ensure the seamless connection of mine in time, space and yield. The hanging wall ore body in the western area of Luodang mining area was taken as the research object. In view of the complex geological conditions that the ore body is located under the high slope and adjacent to the open-pit transportation system, the two-step strip upward horizontal layered filling mining method was adopted. FLAC3D numerical simulation software was used to simulate and analyze the stability of stope, slope and open-pit transportation system in the process of mining. The results show that when the mining method is used to mine the hanging wall ore body, the plastic zone range and the maximum displacement of the stope roof are 3.4 m and 6.6 mm, respectively, and the plastic zone range and the maximum displacement of the slope and open-pit transportation system are 9.5 m and 5.8 mm, respectively. The maximum tensile stress of the stope, slope and open-pit transportation system is 1.2 MPa, and the overall stability is good. In the process of hanging wall ore mining, there is a significant negative correlation between the stope-slope distance with the stability of the stope. The research can provide theoretical reference for the mining of hanging wall ore bodies in similar mines.

To improve the efficiency and accuracy of the mining and stripping plan for large-scale open-pit mines, a dynamic sorting of mining increment bodies(ACO-DP) integrating the ant colony optimization (ACO) algorithm and dynamic programming (DP) method was proposed. Combined with the distributed search mechanism of ACO, the state transition path selection strategy was reconstructed, which significantly reduced the computational complexity. Through its practical application in an open-pit quarry in Guangdong, the significant effects of the ACO-DP method in improving the efficiency of mining and stripping plan, optimizing resource allocation and enhancing economic benefits were verified. The results show that the ACO-DP method shortens the planning time of the quarry from 3 000 minutes to 6.45 minutes, with an efficiency improvement of 99.8%. The stripping ratio is optimized from 0.39 to 0.124, with a decrease of 68.2%, and the net present value gradually increases from 244.99 million yuan to a peak of 253.93 million yuan. The ACO-DP method can be integrated into a mine digital twin system, supporting real-time dynamic adjustment and multi-objective collaborative optimization, and providing a new idea for intelligent mine planning under the "double carbon" goal.

To achieve the mining production capacity of 15 million tons per annum for the transition of open-pit to underground mining project of Sijiaying Iron Mine, the vertical zonal mining method was adopted, and a horizontal isolated pillar was required between the upper and lower mining areas. For improving the overall stability of the mining area, FLAC3D numerical simulation method was used to investigate the evolution characteristics of the stress field, the development law of deformation and failure, and the influence of the horizontal isolation pillar thickness on the surface settlement deformation of the open pit under five different thicknesses. Finally, the safety thickness of horizontal isolated pillar in this mine was determined to be 18 m. The results are concluded as follows. Firstly, with the increase of the thickness of the horizontal isolation pillar, the concentrated stress in the pillar decreases significantly, the distribution of the maximum principal stress tends to be uniform, and the distribution range of tensile stress decreases significantly, mainly in the stope part of the mining panel. Secondly, in the horizontal isolated pillar, the displacement presents an obvious nonlinear decreasing change law with the increase of the pillar thickness. The larger displacement occurs at the position where the pillar is close to the hanging wall of the orebody. When the pillar thickness is 18 m, the maximum displacement is 36.2 mm. Thirdly, the volume of the plastic zone in the pillar shows a nonlinear decreasing trend as the thickness of the horizontal isolation pillar increases. When the pillar thickness is 16 m, the plastic zone is no longer connected. In comparison, when the pillar thickness reaches 18 m, only a small amount of plastic failure occurs locally, and the isolated pillar is in a safe state. Finally, the deformation and settlement amount of the open pit surface gradually decreases with the increase of the thickness of the horizontal isolated pillar, and the position where the maximum displacement occurs is the same as the one where the maximum displacement occurs in the isolated pillar. When the pillar thickness is 18 m, the surface settlement amount of the open pit is 10.8 mm, indicating a good stability.

To address the problems of the determination of the safe thickness and stability of isolated pillars during open-pit to underground mining, taking a domestic metal mine with open-pit to underground mining as the engineering background, dynamic simulation and comparative analysis were carried out on the stopes under the conditions of different isolated pillar thicknesses and different stoping sequences based on the particle safety factor calculation method derived from the twin-shear unified strength theory and numerical simulation. The results are shown as follows. Firstly, when the mining room width is 20 m, the optimal safe thickness of the isolated pillar in the mining room is 39.37 m. At this time, the minimum value of the particle safety factor at the bottom surface of the isolated pillar is 1, which meets the engineering safety requirements. Considering the actual engineering conditions, the isolated pillar thickness is determined to be 40 m. Secondly, the particle safety factor at the bottom surface of the isolated pillar shows a nonlinear growth trend with the increase of thickness, with similar spatial distribution characteristics: the safety factor in the contact area with the hanging wall surrounding rock is lower than that of the footwall, the safety factor at the center of the bottom edge in the width direction of the roof is lower than that at both ends, and the safety factor shows an increasing trend from west to east in the length direction of the roof. Thirdly, mining disturbance leads to the deterioration of the stability of isolated pillars. As the exposed area of the goaf increases, the dangerous range expands accordingly. The closer the particles are to the goaf, the smaller their particle safety factor will be, and the dangerous area migrates from the center of the bottom surface to the midpoint of the long side with the advance of stoping. The proposed thickness optimization method for isolated pillars based on the critical safe thickness threshold and dynamic risk evolution can provide a reference for the problem of determining the safe thickness of isolated pillars in open-pit to underground mining mines.

In response to the mining technical problems of high-grade pillars caused by insufficient preparation in mining levels and stopes, as well as significant fluctuations in ore output grade in a copper-nickel mine, three mining methods were proposed, namely panel mechanized upward drift filling mining method, downward drift filling mining method, and combined mining method of upward drift and strip medium-length hole. The panel mechanized upward drift filling mining method was determined to be the optimal solution with comparative analysis of the advantages, disadvantages, technical and economic indexes of these methods. The classical Janssen theory of granular pressure was used to calculate the overburden load of pillars. The mechanical models of simply supported beam and soft support weak plate were adopted to analyze the relationship between the thickness of artificial false roof and the maximum compressive stress. By comprehensively considering the construction form of artificial false roof and the mechanical properties of cementitious materials, the filling and construction parameters of artificial false roof were determined as follows: the thickness of the artificial false roof is 7.0 m, and the 28-day strength of the filling body is 4.5 MPa. To address the quality, safety and cost problems in the construction of artificial false roof, by optimizing the construction plan, the Optimization Scheme Ⅰ was confirmed as the optimal solution, that is, the artificial false roof serves as the direct roof of the 10 m roof pillar in the lower stope. The artificial false roof adopted a reinforcement design scheme of bottom reinforcement, waist reinforcement and top reinforcement combined. Application results show that the proposed pillar mining scheme is practical and feasible. The panel production capacity of pillar stopes increases to 276 t/d, the pillar recovery rate reaches 82%, and the stope ground pressure activities remain stable. The construction technology of artificial false roof is highly operable, safe and reliable. This scheme has realized the safe and efficient recovery of pillar resources, providing technical reference for pillar mining in similar mines.

Taking a copper mine as the engineering background, optimization research on the parameters of stope mining drifts was carried out to realize the safe and efficient mining of horizontal pillars in underground mines and ensure the stability of stopes. Based on the structural mechanical model of simply supported beam, the law of tensile stress of drift roof varying with drift width was analyzed, and the drift width and reserved roof thickness were initially determined. Further, FLAC3D numerical simulation was used to compare the influence of drift width on the overall stability of stope under different reserved roof thicknesses. The results show that based on the structural mechanical model of simply supported beam, the optimized structural parameters of the drift are a reserved roof thickness of 2 m and a drift width of 4 m. Taking Scheme 3 (drift width of 3.5 m, drift height of 4 m) as an example, theoretical calculation shows that the maximum tensile stress of its roof is 0.37 MPa, and the safety coefficient reaches 1.86.In the numerical simulation, the maximum tensile stress is 0.49 MPa, the stope roof displacement is small, the roof basically does not undergo plastic failure, and the structure remains stable. The method combining the simply supported beam theory and numerical simulation can accurately predict the load changes and stress distribution in the mining of horizontal pillars, and provide a basis for the optimization of structural parameters of mining drift for similar mine projects.

The strength design of filling body is often determined by indoor proportioning test or engineering experience method, but the influences of stope structure parameters such as stope height, stope length and stope width on the strength of required filling body are ignored. Taking a copper mine as the engineering background, based on the L-L strength analysis method, the theoretical strength values of filling body in one-step stope and two-step stope under different structural parameters were calculated by orthogonal tests. The results show that the influence weights of stope structure parameters on the theoretical strength of filling body are ordered as follows: stope height>stope width>stope length. The strength prediction model of filling body in one-step stope and two-step stope was constructed, combined with the existing filling technology, the stope structure parameters were optimized reversely. Finally, the optimal stope structure parameters are recommended as follows: stope height of 5-25 m, stope width of 9-12.5 m, and stope length of 80-120 m. The structural parameters of the stope have been used for on-site production, with strictly controlling the construction specifications of the stope, as well as eliminating the phenomenon of over-excavation and under-excavation. The practical results show that the collapse phenomenon caused by unreasonable structural parameters of the stope and insufficient strength of the filling body basically disappears. The research results can provide reference for the theoretical strength prediction of filling body and the optimization of stope structure parameters.

In order to study the competition mechanism of particle migration and settlement behavior in the process of pipeline transportation of unclassified tailings paste slurry, Electrical Resistance Tomography (ERT) was used to carry out pipeline transportation tests on paste slurry with mass concentration of 60% and coarse particle content of 0, 5%, 10% and 15%, respectively. Based on the Maxwell equation, the conductivity-mass concentration mapping model was established. The plunger flow structure was reconstructed by the conductivity distribution, and the regression equation of the mass concentration and the coarse particle content in the plunger area was established. The results show that the conductivity and slurry mass concentration in the central area of the pipeline are higher than those in the side wall area, and the particle migration behavior forms a typical plunger flow structure. With the increase of coarse particle content, there are "optimal point" (4.3%) and "equilibrium point" (9.6%) of coarse particle content. When the content of coarse particles is 4.3%, the particle migration effect is the best, forming a stable particle structure flow of "fine particles carrying coarse particles". When the content of coarse particles exceeds 9.6%, the settlement effect begins to dominate, and the accumulation of particles at the bottom of the pipeline increases significantly. The ERT technology has successfully realized the dynamic visualization of the concentration field of paste pipeline transportation, revealed the dynamic balance law of particle migration-settlement, improved the stability of "plunger structure" and reduced the risk of plugging, which has a reference value for the safe transportation of paste filling.

In order to achieve efficient and stable continuous preparation of filling slurry, the computational fluid dynamics numerical simulation method was used to compare and analyze the influences of traditional rigid paddle and flexible-guide composite paddles on the flow field structure, velocity distribution and mixing characteristics of multi-state materials during continuous stirring. The action mechanism of the flexible-guide composite paddles on the mixing uniformity, mixing time and energy consumption of the slurry was explored. The technical superiority of the flexible-guide composite paddles in the homogenization stirring of multi-state materials was verified by laboratory tests and industrial applications were carried out. The results show that the flexible-guide composite paddles significantly expand the turbulent kinetic energy distribution range of the slurry through elastic deformation and rigid-flexible coupling, form an axial flow-radial diffusion stirring flow field, and realize the wide-area dispersion of multi-state materials. Compared with the traditional rigid paddles, the particle dispersion efficiency under the flexible-guide composite paddles is increased by 51.8%. Under the equivalent mixing effect, the power of the flexible-guide composite paddles is reduced by 15.3%. Under the equivalent power, the stirring effect of the flexible-guide composite paddles is significantly better than that of the traditional rigid paddles. At present, the flexible-guide composite paddles has been successfully applied to mine production, and the slurry homogenization effect after stirring is excellent. The mass concentration of slurry is stable at 70%, and the fluctuation range is less than 1%. The research can provide a new method for the preparation of fine-grained slurry.

To reveal the synergistic mechanism of mechanical vibration on tailings thickening and sand discharge, based on the mechanism of tailings slurry vibration thickening, an experimental system for vibration thickening independently developed was used to conduct discontinuous thickening and sand discharge experiments under vibration. The technical feasibility of mechanical vibration to improve tailings slurry thickening efficiency and promote underflow activation and sand discharge was verified. The results show that the accumulation of tailings particles in a conical structure within the thickener is the key to improving the mass concentration of the underflow. The eccentric vibration mechanism transmits energy in a sinusoidal harmonic motion, and the excitation range of the vibrating rod is related to the slurry density and vibrator mass. A cylindrical activation region is formed around the vibrating rod during vibration, with a larger radius when the yield stress is lower and the plastic viscosity is higher. Compared with the no-vibration condition, with the increase of feeding velocity under vibration, the underflow mass concentration is increased by an average of 7.74%, the solid content of overflow water is increased by an average of 10.11%, while the increase of the overflow water rising velocity is not obvious. The research results provide a basis for the development of mechanical vibration-assisted high-efficiency thickening equipment.

The security of shaft safety pillar is an important guarantee for safe mining in mines. The ground pressure activities in the mining area around the safety pillar of a gold mine were investigated and analyzed. Combined with the main risk factors, a security evaluation model considering multiple influencing factors was proposed, and the current safety evaluation of the mining area around the shaft safety pillar was evaluated. The research shows that the shallow ground pressure activity is caused by the combined action of geological factors and mining disturbance. The deep local deformation and failure are caused by the comprehensive influences of mining depth, in-situ stress increase and geological factors. The security of the safety pillar is affected by three types of factors, such as natural conditions, mining disturbance and production management, involving 11 influencing factors. The security evaluation of 41 stopes show that the safety level of most stopes is grade II, and the overall safety situation is good. The occurrence conditions of ore bodies, geological structure, mining methods and position of shaft safety pillars are the main factors affecting the security of pillars. In addition, stoping areas farther away from the shaft safety pillars exert less mining disturbance on the shaft zone, resulting in higher security of the safety pillars.

Taking Qidashan open-pit stope as the research object, field investigations were carried out. Fixed-point and vehicle-mounted mobile continuous monitoring was conducted during the drilling, blasting, loading and transportation stages, with meteorological parameters recorded and the dust migration process photographed. Based on the field monitoring data, an analysis was conducted on the dust dispersion characteristics and influence mechanism in different stages during the production process of the open-pit mine. The results show that there is a significant correlation between PM_2.5 and PM₁₀ concentrations. The cubic polynomial curve model has the highest goodness of fit, with a coefficient of determination of 0.945, and exhibits the strongest explanatory power for this relationship. The average dust emission concentrations and diffusion ranges differ significantly among different production stages. The blasting stage has the highest dust emission concentration in a single operation, reaching 324.4 μg/m³, and its dust diffusion range is the widest. The dust emission concentrations of a single operation in the drilling, loading and transportation stages are 59.8 μg/m³, 88.2 μg/m³ and 61.8 μg/m³, respectively. In addition, the dust concentration in the pit bottom area is significantly higher than that at the bench crest, with its mean value being approximately five times that of the dust concentration at the bench crest. The research results reveal the variation laws of dust concentration in open-pit stopes and can provide theoretical support for dust prevention and control.

The temperature field of deep tunnels and the development of deep mineral resources involve the thermal conductivity of rock mass. For the nonlinear change rule of effective thermal conductivity of fractured rock mass under normal stress, based on the two-part Hooke's model and effective thermal conductivity series-parallel theory, a theoretical model of effective thermal conductivity of fractured rock mass under normal stress was established, and the influences of model parameters on the effective thermal conductivity of fractured rock mass under stress were analyzed. Through the numerical simulation results of the change of temperature field in Nigel Tunnel, the reliability in engineering application of the model was verified. The results show that, the theoretical model prediction results are in good agreement with the test data. The effective thermal conductivity of the fractured rock mass in the low stress stage is mainly affected by the soft part of the pore-slit closure, and increases nonlinearly with the increase of the stress. While the effective thermal conductivity of the fractured rock mass in the high stress stage is mainly affected by the hard part of the pore-slit closure, and increases slowly in an approximately linear manner with the increase of the stress. The larger the angle between the fracture surface and the direction of heat transfer, the smaller the effective thermal conductivity of the rock at the same stress, and the higher the degree of non-linearity with the stress change. Comparing the numerical simulation results with the measured data, the thermal conductivity of the intact rock mass is on the large side, the effective thermal conductivity obtained by the stress-independent effective thermal conductivity model is on the small side, and the coupling model of normal stress and thermal conductivity is more in line with the actual measured values.

To investigate the impact of underground paste backfill on the groundwater environment in a lead-zinc mine, the variation laws of pH and electrical conductivity of soaking solution and leaching solution affected by backfill mass concentration and cement-sand ratio were systematically examined by carried out backfill soaking and leaching tests. The results show that the electrical conductivity of the soaking solution and leaching solution exhibits a trend of first increasing and then decreasing over time. When the cement-sand ratios are 1∶4, 1∶10 and 1∶20, the maximum electrical conductivity values of the soaking solution are 2 050 μS/cm, 1 910 μS/cm and 1 220 μS/cm respectively. Meanwhile, the decreasing rates of pH of the leaching solution are 0.11 d^-1, 0.12 d^-1 and 0.18 d^-1 in the first 14 days, and 0.08 d^-1, 0.06 d^-1 and 0.03 d^-1 in the subsequent 14 days. This indicates that the higher the cement-sand ratio, the smaller the pH decrease range of the soaking solution, the higher the maximum electrical conductivity value, the slower the pH decreasing rate of the leaching solution in the early stage, and the faster the decreasing rate in the later stage. The mass concentration has a relatively minor effect on the variation of pH and electrical conductivity of the soaking solution and leaching solution over time. The leaching behavior of toxic ions is jointly determined by the adsorption of hydration products and the effect of pore structure, and the early stage is dominated by hydration reactions while carbonation reactions exert a more prominent influence in the later stage. The research results show that the concentration of heavy metal ions released by the backfill is far lower than the allowable values of relevant national standard, indicating that this paste backfill scheme has favorable environmental protection performance.

Microbially Induced Carbonate Precipitation (MICP) technology shows remarkable potential in tailings pond ecological reinforcement projects due to its environmental friendliness and sustainability characteristics. However, the quantitative study of seepage diffusion during microbial grouting remains a key constraint to its application. Aiming at multi-round microbial grouting reinforcement scenarios and systematically considering the synergistic effect of the sandy soil medium on the slurry diffusion behaviour during the dynamic attenuation of permeability coefficient and the evolution of porosity gradient, a permeability diffusion radius prediction model based on the column diffusion theory was constructed by combining the multi-scale tests and theoretical modelling with a combination of one-dimensional sand column experiments, intermediate-scale 2D planar physical model experiments, and FLAC3D numerical simulations of coupled flow and solidity. The results are concluded as follows. The vertical dimension is dominated by gravity effect, and the slurry diffusion shows significant asymmetry, forming a pagoda-like distribution with the bottom wide and the top narrow, and the final diffusion radius at the bottom is 3.91 times of the diffusion radius at the top. The horizontal dimension follows the radial attenuation law of diffusion effect, and the reinforcement strength is inversely proportional to the centre distance of the slurry injection pipe. Validation of the theoretical model shows that the relative errors between the maximum diffusion radius and the predicted value for the 2nd to 5th rounds of grouting were 43.89%-63.72%, and the error ranges were within reasonable limits. The research results can provides a quantitative theoretical framework for the optimisation of MICP process parameters and engineering-scale diffusion prediction.

In order to study the influence of saturation time on the mechanical properties and crushing law of phosphate rock, the static and dynamic mechanical tests under different strain rates were carried out on the natural, saturated 48 hours and saturated 3 months of phosphate rock. The test results show that under the condition of static load (low strain rate), the strength of ore rock decreases with the increase of saturation time, but the strength reduction rate shows a trend of fast first (within 48 hours) and then slow. The compressive strength of ore rock saturated for 3 months is 21% lower than that of saturated for 48 hours. Under the condition of dynamic load (medium and high strain rate, 43-146 s^-1), the strength of ore rock is affected by the mutual game and synergistic effect of weakening and strengthening of free water in the ore rock. With the increase of saturation time, the strength of ore rock increases firstly and then decreases. The dynamic compressive strength of ore rock saturated for 3 months is the smallest, which is reduced by 25.9%-28.5% compared with that for 48 hours, and reduced by 7.0%-19.7% compared with that under natural state. Saturation effect can improve the sensitivity of dynamic compressive strength of rock to strain rate. The crushing form of ore rock is closely related to its strength. The larger the dynamic compressive strength, the smaller the fragmentation after crushing. In the same strain rate range, the average particle size of the ore rock after the impact from large to small is the ore rock saturated for 48 hours, the ore rock in the natural state, and the ore rock saturated for 3 months. Long-term saturation (such as 3 months and above) will significantly reduce the strength of ore rock and make the crushing more thorough. At this time, the unit consumption of explosives can be appropriately reduced to avoid safety hazards such as flying stones caused by excess energy.

Over-exploitation of mineral resources aggravates the ecological environmental pressure in mining areas. As solid wastes containing potential heavy metals, tailings cause damage to soil organic matter (SOM) through stockpiling, which has become a key issue in ecological restoration. The SOM monitoring system of tailings was established based on hyperspectral remote sensing technology. Taking a mining area in Tangshan, Hebei Province as the research object, vegetation canopy hyperspectral data were obtained using an ASD ground spectrometer and GF-5 satellite, and tailings samples at the corresponding points were collected for physicochemical property analysis. After screening sensitive bands with the Boruta algorithm, four types of models such as multiple stepwise linear regression (SMLR), partial least squares regression (PLSR), random forest (RF) and extreme gradient boosting (XGBoost) were constructed and verified for accuracy. The results show that the XGBoost model has the best prediction effect on the ground ASD spectral data (R²=0.92, RMSE=0.37), which is suitable for fine monitoring. The GF-5 satellite data perform best with the XGBoost model (R²=0.73, RMSE=0.53), which meets the needs of large-scale rapid assessment. The study confirms that ground-space multi-scale SOM monitoring can be realized through the collaborative optimization of spectral mathematical transformations and linear and nonlinear models, with efficiency significantly enhanced compared with traditional detection methods. The research results can provide a scientific basis for ecological restoration of mining areas, promoting environmental management of mining area and the sustainable development of mining industry.

The restoration of the geological environment in abandoned mines is an important approach to resolving the contradiction between mineral resource development and ecological protection, and it is also a significant measure to implement the deepening of the ecological civilization system reform. It plays a crucial role in building a beautiful China and improving the living and production environment and standards of the people. To better restore and utilize the historical abandoned mines in Zhangjiakou City, based on remote sensing monitoring, through methods such as data collection and on-site investigation, the current situation and characteristics of abandoned mines were statistically analyzed, common problems were summarized, and countermeasures and suggestions for geological environment restoration were proposed in combination with the local characteristics and conditions of the abandoned mines. The results are concluded as follows. Firstly, by the end of 2023, the identified un-restored historical abandoned mines is 475 in various regions of Zhangjiakou City, covering an area of approximately 11.29 square kilometers. Secondly, due to the long-term extensive mining activities, about 685.52 square kilometers of terrain and landscape have been damaged, causing severe visual pollution and local ecological environment damage. Thirdly, large-scale abandoned mine areas generally have five types of problems, including terrain damage, geological disasters, land occupation, water ecological destruction and serious damage to soil vegetation. These problems have caused relatively serious impacts on the geological and geomorphological conditions, land and water resources, the safety of residents' production and life, and biodiversity in the mining areas and their surroundings. Finally, it is suggested to plan the work based on the working concept of "conforming to nature, systematic restoration, highlighting key points, adapting to local conditions, innovating mechanisms, and policy-driven", and an integrated interactive restoration model for abandoned mines with ecological restoration, industrial restoration, and value restoration as the framework has been proposed. The combination of geological environment restoration with industry and economic development will be explored to achieve the superimposed effects of economic, ecological, and social benefits, providing a reference for the restoration of the geological environment in abandoned mines and the promotion of green mine construction in China.

Green and low-carbon transformation of the mining industry is a key link for achieving high-quality development. From the perspective of the "Double Carbon" goal, an evaluation index system for the green and low-carbon development level was constructed from four aspects: economic development, production scale, environmental pressure, and low-carbon level. Through the game theory combination weighting method and the cloud matter-element model with improved cloud entropy, the green and low-carbon development level of Guangxi mining industry was evaluated, and its influencing factors were further analyzed in combination with the grey correlation degree and obstacle factors. The research results show that, from 2005 to 2022, the evaluation grade of the green and low-carbon development level of Guangxi mining industry experiences a process of first rising slowly, then declining, then rising again and tending to stabilize, gradually improving from the backward stage (Ⅳ) to the advancing stage (Ⅱ), with obvious overall fluctuations. Besides, the grey correlation degree results show that the proportion of large-scale mining enterprises in the mining industry, the development level and development potential of the mining industry are key influencing factors, with grey correlation degrees of 0.862 3, 0.808 7 and 0.793 8 respectively. The obstacle factors show phased changes. From 2005 to 2018, low-carbon level and environmental pressure exert a greater hindrance to the green and low-carbon development level, while the hindrance degree of economic development is more significant from 2018 to 2022. The research results can provide a reference for the green and low-carbon transformation of the mining industry.

With the intensification of China's population aging, the traditional mine operation mode relying on the experience of technicians can no longer meet the needs of the sustainable development of modern mining. There is an urgent need to introduce advanced technologies such as digital twins to promote the transformation of mines towards intelligence and greening. With its data-driven characteristics, digital twin technology can provide accurate simulation for mine construction plans. By integrating multi-source data such as geological and geographical data, a virtual model corresponding to the real mine was constructed to optimize the layout planning and reduce resource waste and risks in actual construction. Data-driven digital twin technology has been increasingly applied in scenarios such as mine construction planning, mine production safety, and mine production optimization. However, restricted by the current cognitive level, technical capacity, and infrastructure conditions, the constructed virtual models cannot fully guarantee authenticity and reliability of data, leading to deviations in prediction results. By constructing a complete standard system, enhancing data fusion and processing capabilities, optimizing intelligent algorithms and models, and strengthening interdisciplinary cooperation and technology integration, the mining industry is driven toward unmanned and intelligent transformation.

To address the problems of low accuracy, poor reliability and high maintenance costs in the internal attitude measurement of hydraulic supports, a study on the virtual-reality synchronous mapping method for digital twin monitoring of hydraulic support attitude was carried out. Firstly, by analyzing the support structure, a parametric expression model for the internal attitude of the hydraulic support was established, and the key technologies for sensor data processing were investigated. Then, a motion simulation model of the hydraulic support was established, and the parametric expression model of the hydraulic support was incorporated into the bottom layer of the simulation system for preliminary application. Finally, based on laboratory conditions, test verification was carried out on the proposed virtual-reality synchronous mapping method for support attitude. The test results show that the errors of the internal attitude angles of the support measured by this method are all controlled within 2°, which can meet the actual monitoring requirements. The research results provide new ideas for the virtual-reality synchronous mapping of hydraulic supports and have certain significance for the intelligent construction of mines.

Non-explosive mechanical excavation mining has the advantages of small disturbance, high efficiency, low support cost and good roadway shaping effect compared with drilling and blasting method, and the optimal selection of pick parameters is of great significance to efficient excavation. Based on the measured ground stress data and rock mechanics test results of the -525 m, -606 m, and -653 m sections of a certain metal mine, a PFC particle flow rock breaking model of picks was established. Numerical simulation analysis of pick rock breaking after unidirectional unloading was conducted with three types of intrusion angle of 90°, 60°, and 45° under three different stress levels in the middle section. The research results indicate that as the stress level increases, the area of dense nuclei formed by the pick breaking decreases, the length of the strip-shaped crack propagation shortens, and the number of microcracks generated during the rock breaking process also decreases, indicating that high stress conditions have a suppressive effect on rock fragmentation. Under the 45° intrusion angle rock breaking mining, the traction and cutting force fluctuations of the cutting tooth are small and the cutting force always maintains a high level. At the same time, the number of microcracks generated by rock breaking at a 45° intrusion angle is much greater than that at 60° and 90° intrusion angles. Combining the comprehensive analysis of mechanical response and rock fragmentation effect, the 45° intrusion angle has the optimal rock breaking performance at varying stress levels.

Aiming at the problems of spatial information loss in traditional 2D images and the one-sidedness of single-cell data during the identification of coal slime flotation froth, a multi-cell feature fusion method based on 3D point cloud data was proposed. The Percipio Infrared Binocular FM855-E1 industrial camera was used to collect the 3D point cloud data of the froth surfaces from each flotation cell. Preprocessing and data augmentation techniques were adopted to optimize the dataset. A PointNet network with non-shared weights was utilized to extract the high-dimensional features of each cell. After dimensionality reduction by a multi-layer perceptron, these features were fused into multi-cell forth features through a concatenation function. Finally, the working condition categories were determined by a combination of a multi-layer perceptron and the Softmax function. The experimental results show that the classification accuracy of the multi-cell network reaches 94.89%, which is higher than other networks, the loss value is reduced to 0.216 9, with excellent robustness and generalization ability. It is proved that the multi-cell forth feature fusion method can significantly improve the recognition accuracy of flotation conditions, and provide a high-reliability three-dimensional visual solution for the intelligent flotation of coal slime.

In order to meet the requirements of lightweight and explosion-proof safety of coal mine equipment, a type Ⅰ non-metallic lightweight explosion-proof enclosure with a volume of 19.5 L was prepared by glass fiber/epoxy resin composite (GF/ER). The comprehensive performance of GF/ER explosion-proof enclosure was analyzed by material performance tests, finite element simulation and multiple explosion-proof safety tests. The results show that the GF/ER explosion-proof enclosure meets the requirements of high mechanical strength, high flame retardancy (V-0 grade) and antistatic property of underground coal mine equipment. The change rates of tensile properties, bending properties and impact strength of GF/ER explosion-proof enclosure are less than 10%, indicating that it has excellent durability and environmental adaptability. In the reference pressure test, the maximum explosion pressure of the GF/ER explosion-proof enclosure is 0.496 MPa, the ultimate bearing capacity is 3.1 MPa, far exceeding the standard requirement of 1.5 MPa. Under the working load, the gap deformation of the GF/ER explosion-proof enclosure is less than 0.15 mm, and the structure is stable and reliable. Compared with the same size metal explosion-proof box, the GF/ER explosion-proof enclosure achieves more than 50% weight reduction effect, significantly reduces the burden of downhole operation, and improves the endurance of mobile equipment. The research results can provide a feasible technical path and theoretical basis for the lightweight of mining equipment.

Anshan-type hematite accounts for about 55.20% of the total identified iron ore resources in China, and its flotation generally requires high temperature (about 35 ℃ or more) conditions, which increases the production cost. Therefore, the flotation behavior of hematite and quartz was studied with a self-developed MY-type collector and compared with the sodium oleate flotation system. Utilizing detection and analysis techniques such as contact angle, Zeta potential and infrared spectroscopy analysis, the action mechanism of MY on mineral surface was discussed. The results of single-mineral flotation experiments show that under the temperature range of 15-35 ℃, the pH of 11.5, and the dosage of 200 mg/L, the MY-type collector can achieve recovery rate of quartz and hematite exceeding 87.25% and 92.50% respectively. At 25 ℃, under the interaction of the three agents of starch, CaO, and collector, the maximun difference in single mineral recovery rate of quartz and hematite is 89.25 percentage points under the MY flotation system, which significantly improves the difference in the flotation of quartz and hematite compared to the sodium oleate flotation system (the maximun difference in recovery rate is 56.25 percentage points). The mechanism analysis results indicate that MY collector exhibits multifaceted synergistic adsorption effects on quartz mineral surfaces, including electrostatic adsorption, hydrogen bonding, and chemical bonding, while on hematite surfaces, it primarily involves molecular adsorption and electrostatic adsorption. Due to the presence of multiple active groups such as S＝O, —NH₂ and C＝O in its structure, MY forms coupled synergistic interactions across multiple active sites, enhancing its quartz recovery capability. This also amplifies the floatability difference between quartz and hematite, effectively promoting the separation of hematite and quartz in the room-temperature reverse flotation system.

Taking a graphite ore in Luobei, Heilongjiang Province as the research object, in order to improve the fixed carbon content of graphite flotation concentrate, through pure mineral flotation test, the mechanism of typical gangue quartz entering graphite concentrate was analyzed, and the effects of ultrasonic time and ultrasonic power on the flotation of graphite and quartz artificial mixed ore were explored. The actual ore flotation test was carried out by ultrasonic assisted process to evaluate the effect of ultrasonic pretreatment on the fixed carbon content of graphite concentrate. The results of pure mineral flotation tests show that graphite forms flocs under hydrophobic interaction, causing fine-grained quartz to enter the concentrate through entrainment and inclusion. Ultrasonic pretreatment can strengthen particle dispersion, reduce water recovery and reduce quartz floating. The actual ore flotation test show that the graphite concentrate with fixed carbon content of 94.61% and recovery rate of 81.66% is obtained by using the open-circuit flotation process of "five grindings and six flotations" and ultrasonic pretreatment for 3 min before the third re-election to the sixth re-election flotations. The fixed carbon content of the concentrate is 3.10 percentage points higher than that without ultrasonic treatment. The research results provide a reference for improving the fixed carbon content of graphite concentrate in the re-grinding and re-flotation stage by ultrasonic assisted process.

To improve the inhibition performance of causticized starch and the recovery rate of iron concentrate in the process of reverse flotation desilication of iron ore, the Box-Behnken design of response surface methodology was adopted to systematically investigate the effects of three factors of causticizing time, causticizing temperature and causticizing ratio, as well as their interaction on the recovery rate of iron concentrate. The results show that causticizing temperature exerts the most significant impact on the recovery rate, with the order of significance of influence being: causticizing temperature >causticizing time >causticizing ratio. Among them, the interaction between causticizing temperature and causticizing ratio also has a significant effect. The optimal preparation conditions obtained through optimization are as follows: causticizing temperature of 95 ℃, causticizing time of 80 min, and causticizing ratio of 0.07. Under these conditions, the recovery rate of iron concentrate reaches 63.65%, which is 1.3% higher than that under the initial conditions. Infrared spectroscopy analysis results show that after optimization of preparation conditions, the intensity of O—H, C＝O, C—OH and C—O—C characteristic peaks of causticized starch is significantly enhanced, indicating that the intramolecular hydrogen bond network is more stable, the structure is more orderly, and the inhibition performance is significantly improved. The research results verify the effectiveness and reliability of the response surface methodology in the optimization of flotation reagents, and provide a theoretical basis and technical support for the industrial application of causticized starch.

To provide a basis for the feasibility evaluation of comprehensive utilization of a certain tungsten polymetallic mineral resource, detailed process mineralogy studies and preliminary beneficiability evaluations were carried out. Firstly, the mineral liberation analyzer (MLA), combined with various analytical methods such as microscopic identification, chemical analysis, X-ray diffraction analysis, was employed to investigate the chemical composition, material composition of the ore, as well as the key process mineralogy characteristics such as the output form, dissemination particle size and dissociation degree of the main target minerals. Then, according to the characteristics of the ore, the main mineralogy factors affecting the beneficiation effect were discussed and analyzed. It was recommended to adopt the beneficiation process flow of "pre-concentration and discarding waste-gravity separation and enrichment-selection and quality enhancement-fine mud returning to the circuit-comprehensive recovery of sulphide ores". The process of "flotation-shaking table gravity separation-centrifugal gravity separation" was simplified, and ore beneficiability tests were conducted. The results show that the original ore belongs to granite-type disseminated tungsten ore containing molybdenum and bismuth. The main valuable component is WO₃, with a content of 0.31%. The main associated components are Mo and Bi, with contents of 0.043% and 0.024%, respectively. Sulfide ores with Mo grade of 1.40% and Bi grade of 0.79%, and recovery of 97.51% and 84.67%, respectively, and tungsten concentrate with WO₃ grade of 69.00% and recovery of 76.58% are obtained by beneficiability tests. The total recovery rate of WO₃ is 87.04% if the WO₃ in fine mud rough concentrate and tungsten intermediate ore is included in the calculation. The test verifies that the ore has good beneficiability and recovery value.

The comprehensive utilization of tailings is one of the key aspects of green development in the mining industry, and the preparation of geopolymers by tailings holds significant promise. Due to the low reactivity of tailings, thermal-alkali activation can effectively enhance their reactivity, thereby optimizing the performance of geopolymers. To characterize the changes in phase composition and chemical bonds during the activation process, exploring the activation mechanism, X-ray diffraction (XRD) and Fourier-transform infrared spectroscopy (FTIR) were employed. The results indicate that the 7-day compressive strength of thermally-alkali-activated tailings geopolymers can reach up to 15.58 MPa, representing a more than tenfold increase compared to non-activated samples. The compressive strength of the geopolymers improves with the rise of alkali content, calcination temperature and calcination duration. During the thermal-alkali activation process, muscovite in the tailings undergoes structural distortion through group substitution and is converted into an amorphous phase. The alkali content and calcination temperature has a notable impact on the activation effect. The research findings can provide a theoretical foundation for the selection and activation of tailings in geopolymer preparation.