To address the stability challenges of stopes under high in-situ stress and complex geological conditions in deep mining operations, based on the engineering background of Sishanling Iron Mine, a "theoretical-empirical-numerical" collaborative optimization method for the stope structure parameters was established. Firstly, using the Mathews stability graphical method, the exposed area of the stope and the safety range of the pillars were initially screened based on the correction value of the Q system and the shape factor. Secondly, through engineering analogy analysis of the experience of similar stopes in both domestic and foreign regions, the reasonable exposed area of the roof and the geometric parameters of the stope were determined. Finally, a three-dimensional discrete element numerical simulation was employed to construct the mining excavation model. The stress, displacement, volume of the plastic zone, and the number of tensile fractures for the three different mining structure parameter schemes were quantitatively evaluated to determine the optimal scheme. The results show that the optimal parameters for the mining room are 80 m (length）×20 m (width）×60 m (height). The roof settlement (1.76 cm) and sidewall displacement (4.46 cm) of this scheme are both below the safety threshold, and the volume of the plastic zone (23 543 m³) and the number of tension fractures (2 157) are significantly better than those of other schemes. After the stope excavation, the roof of the working face mainly undergoes tensile failure, while the side walls exhibit a mixed failure mode of tension and shear. This stress redistribution characteristic provides a quantitative basis for the design of support structures and disaster prevention. The multi-method collaborative optimization system provides a scientific basis for the design of stope structure parameters, and has significant engineering reference value for deep well mines with a depth of several kilometers.

Accurately understanding the instability mechanisms of surrounding rock in deep hard rock roadways is of great engineering significance for the design of roadway support parameters. Taking the kilometer-deep marble roadways at the Jinchuan mine as the research object, a self-defined heterogeneous material program was developed based on the voronoi joint network and Weibull distribution function built in RS2 using the continuous-discontinuous numerical simulation method. A heterogeneous-joint finite element model for the rock and rock mass was established, the deformation parameters and mechanical parameters of marble were calibrated, and the deformation and failure law of deep hard rock was revealed. Meanwhile, considering the joint characteristics of the surrounding rock in the roadway, a heterogeneous-joint finite element model for the roadway was constructed, which reproduced the failure characteristics of deep hard rock roadways. A local support scheme was proposed to address the failure laws of unsupported roadways. The study indicates that the rock and rock mass models constructed based on the heterogeneous-joint finite element method can effectively characterize the deformation and failure laws of deep hard rock. The simulation results of the heterogeneous-joint finite element roadway model are consistent with the the field roadway damage, thereby validating the rationality of this method. Compared with the unsupported condition, the maximum depths of the plastic zones in the left and right ribs of the roadway were reduced by 62.9% and 58.0% respectively after the application of the local support scheme, the numbers of block and joint failures decreased by 83.0% and 74.5% respectively, and the maximum deformation of the roadway was reduced by 33.8%, which verifies the reliability of the local support scheme. The research results provide a reference for the analysis of failure characteristics of surrounding rock in deep hard rock roadway, and expand the idea of deformation control of surrounding rock in deep hard rock roadway.

As mining depths increase, the synergistic effect of high in-situ stress and complex geological environments leads to frequent rock burst incidents. However, there is carrently a lack of comprehensive evaluation methods for the rock burst proneness of deep rock masses that accounts for multi-factor influences. Based on rock mechanics parameter tests conducted at an iron mine in the Xinjiang Uygur Autonomous Region, the rock burst proneness of the rock mass in the -450 m to -600 m level was evaluated using four indicators: the strength brittleness coefficient, the improved brittleness index, the maximum storage elastic strain energy, and the strain energy index. The results indicate significant dispersion among the evaluation results obtained by using different single indicators, rendering it difficult to accurately determine the actual rock burst proneness relying solely on an individual metric. Consequently, a comprehensive evaluation model for rock burst proneness was established by integrating the fuzzy mathematics method and the entropy weight method. A comprehensive assessment of the sandstone rock burst proneness in the -450 m to -600 m level of the mine was performed, revealing a moderate rock burst proneness across all cases. On-site investigations demonstrate that the evaluation results generated by the multi-indicator comprehensive evaluation method based on fuzzy mathematics align closely with the actual in-situ damage conditions, facilitating an accurate assessment of the rock burst proneness grade. These findings provide a rock bust theoretical basis and technical support for safe mine production and rock burst mitigation.

Deep vertical shafts are critical passages for deep resource development, and their surrounding rock stability is essential to guarantee the safety and efficiency of mining. Aiming at the surrounding rock stability problem of shaft walls in broken rock mass, taking the Xiling mining area of Sanshandao Gold Mine as the engineering background, a three-dimensional numerical model of the vertical shaft was established by using the Bonded Block Model (BBM) in the discrete element software. The damage and failure characteristics of shaft walls at buried depths of 1 600-2 500 m were investigated, and six support and reinforcement schemes for shaft walls in high-stress and broken rock mass conditions were proposed. The results show that the deformation and failure behavior of surrounding rock in deep vertical shafts under high in-situ stress is affected by horizontal geostress. With the increase of buried depth, the maximum displacement and deformation range of shaft wall surrounding rock increase. The displacement in the maximum principal stress direction changes significantly, and the minimum principal stress direction is the main concentration area of shear stress. Broken rock strata increase the mechanical complexity of shaft wall surrounding rock, and the dynamic action of broken rock mass may cause spalling of rock blocks and failure of surrounding rock. Grouting bolts can effectively improve the stress state of the support structure and disperse the concentrated stress in the surrounding rock. After support, the displacement of the shaft wall is reduced by 53%-65%, and the shear stress concentration zone is transferred to the shallow part at 0.5-1 m depth of the shaft wall. For different buried depths, reasonable support and reinforcement measures can effectively control the dynamic action of broken rock mass and reduce the failure risk of shaft walls.

With the acceleration of deep-sea development, the conflict between discharge risks and legal regulatory conflicts arising from deep-sea mining in international seabed area needs to be resolved. To this end, starting with a fundamental interpretation of mining discharges, a systematic review of the game process for mining discharge regulations within the "region" was conducted, revealing the fragmented and ambiguous nature of the current international legal framework. By analyzing the challenges in applying the international legal regime for mining discharges, the disconnect between domestic and international laws, and the lag in environmental risk prevention mechanisms, the key difficulties in governance were identified. It further proposes establishing a collaborative mechanism for legal interpretation under a dynamic system, advancing substantive development through inter-convention institutional cooperation, and designing tiered and categorized risk prevention and emergency response mechanisms to achieve coordinated optimization of mining discharge regulations. Against the backdrop of China's strategic requirements, the nation can transition from a rule-follower to a rule-setter by revising domestic deep-sea mining legislation, deepening regional cooperation, and actively championing proposals such as the "negative list" on international platforms. This approach not only offers a viable solution for the negotiation and cooperation on deep-sea mining discharge regulations within the "area", but also provides a practical model for global governance.

Addressing the challenges of complex and variable boundaries, low ore recovery rates, extensive roof exposure areas, and a low degree of mechanization associated with high-altitude tourmalinite-type massive orebodies, this study systematically analyzed the occurrence characteristics of the orebody to facilitate safe, efficient, and green mining operations. Four technical mining schemes were proposed, and their respective advantages, disadvantages, principal technical and economic indexes were comprehensively evaluated. Consequently, the upward drift filling mining method was identified as the optimal extraction scheme. The maximum allowable exposed areas of the orebody and surrounding rock were determined using the Mathews stability graphical method. Coupled with numerical simulations, the distribution patterns of stress, vertical displacement, and plastic zones under varying drift dimensions were elucidated, establishing the optimal drift parameters as 5 m in width and 3.5 m in height. On-site industrial tests demonstrate that the maximum roof subsidence of the stope is 19.2 mm, with no occurrences of collapse. Furthermore, the ore loss and dilution rates are 3.2% and 3.5%, respectively, representing significant reductions of 8.8 and 8.5 percentage points compared with the shallow-hole shrinkage mining with subsequent backfill method. These findings establish a robust technical paradigm for analogous mines and propel the sustainable development of high-altitude mineral resources.

Addressing the issue of top pillar recovery beneath the overlying graded tailings backfill at the Liutangfang Iron Mine in Anhui, this study first comprehensively determined the maximum recoverable thickness of the top pillar using the load transfer line intersection method, the thickness-to-span ratio method, and the Protodyakonov arch theory. Subsequently, the maximum exposed area of the top pillar under varying stope widths was established via the Mathews stability chart method. Finally, incorporating on-site mining practices, numerical simulations of excavation were performed for two mining methods (cross-vein and strike-vein) across five stope structures. A comprehensive analysis was conducted to evaluat roof settlement, stress distribution, plastic zones, and excavated ore volume under different mining methods and stope structural parameters. The results indicate that for a stope span of 6 m, the safe thickness of the top pillar is 5 m. Based on the actual hydraulic radius derived from the Mathews stability chart method, the calculated maximum stope drift length is 30 m. When the strike-vein mining method is employed, the roof settlements corresponding to different drift pillar widths are 16 mm, 18 mm, and 20 mm; when cross-vein mining method is used, the maximum roof settlement is 33.52 mm, with the maximum roof stress increasing by 0.1 MPa. A comprehensive comparative analysis reveals that adopting the strike-vein mining method with a 4 m drift pillar keeps roof settlement within a controllable range, thereby optimally satisfying the safety, efficiency, and economic prerequisites of mine production. This scheme is projected to recover approximately 480 000 tons of top pillar resources, ensuring a smooth transition in mine production capacity and providing a reference for similar engineering projects.

Against the backdrop of panel mining utilizing the stage open stoping with subsequent backfill method during the transition from open-pit to underground mining at Sijiaying Iron Mine, three stope mining sequence schemes were proposed: "from one side to the other" "from the center to both sides", and "from both sides to the center". A numerical simulation approach was employed to investigate the stress field distribution characteristics, displacement variations, and plastic zone propagation laws of the surrounding rock in the panel stope under different mining sequences. Ultimately, the "from the center to both sides" sequence was determined to be the optimal mining scheme for this mine. The results are shown as follows. Firstly, across the three mining schemes, the compressive stress following stress release, the tensile stress, and the maximum internal displacement within the surrounding rock consistently exhibit a trend of "from the center to both sides" < "from both sides to the center" < "from one side to the other". Secondly, under the "from the center to both sides" scheme, the compressive stress and maximum tensile stress of the surrounding rock following stress release are 1.58 MPa and 0.35 MPa, respectively, with a maximum internal displacement of 37.765 mm; these values are universally superior to those of the other two schemes. Finally, following panel extraction, the total volume of the plastic zone in the surrounding rock, and the volume ratio between the tensile plastic zone and the total plastic zone, exhibit the same variation law as the surrounding rock stress field and displacement field. Specifically, the "from the center to both sides" scheme yields a total plastic failure volume of 34.73×10⁴ m³ and a tensile plastic zone ratio of 60.60%, both of which outperform the alternative schemes. These findings hold significant implications for guiding the design and future production of the mine during its transition from open-pit to underground operations.

To address the problem of a large amount of overlaid ore by the shaft safety pillar in a gold mine, numerical simulation calculations method were carried out to analyze the influence of different delineation angles of the safety pillar on the stability of the shaft and surrounding rock, and the safety pillar range was re-delineated. The numerical simulation results show that the influence of mining of No.13 ore vein of the mine on shaft stability increases with the increase of the delineation angle of the safety pillar. When the delineation angle of the safety pillar exceeds 75°, ground pressure behavior is significantly intensified, and there exists a risk of shaft instability, especially after the stoping of deep stopes. Therefore, it is recommended that the delineation angle of the safety pillar be controlled at 75° and below to ensure the safety of the shaft. When the delineation angle of the safety pillar is increased from 65° to 75°, the volume of overlaid ore in the safety pillar is reduced from 1 192 955.0 m³ to 545 256.7 m³.About 54.3% of ore resources can be released, which improves the utilization rate of mineral resources and is conducive to the sustainable development of the mine.

The high content of phosphogypsum gel material has the disadvantages of weak gelling and low strength. Adding lime can improve the gelling and strength of phosphogypsum-based solid waste gel material. Phosphogypsum, steel slag and blast furnace slag were used as raw materials of cementitious materials, lime was used as activator, and tailings were used as aggregate to prepare backfill. The mechanical characteristics, pore characteristics and microstructure of backfill under different lime content were investigated. The fractal theory was introduced to explore the effect of lime on the pore characteristics of phosphogypsum-based solid waste cementitious backfill. The results show that a lime content of 2% increases the 7-day and 28-day strengths of the backfill by 133.33% and 95.83% respectively, which is the best lime content. Excessive lime generates excessive Ca(OH)₂ crystals, which causes volume expansion and structural damage of the backfill, thereby reducing its strength. Lime has a significant effect on the small pores in the backfill, especially on the fractal dimension of the pores within 20-200 nm. The strength of the backfill decreases linearly with porosity, decreases exponentially with pore contents in the ranges of 20-100 nm and >200 nm, decreases quadratically with pore content in the range of 100-200 nm, and increases exponentially with the fractal dimension.

Caving mining is widely recognized to trigger large-scale strata movement and ground deformation, making a reliable delineation of the surface subsidence range essential for mitigating associated losses. In this study, a representative metal mine adopting the caving method was investigated, and the subsidence range was evaluated using numerical simulation, analytical modelling, and similarity simulation model test. Numerical simulations were first performed to obtain a preliminary subsidence profile. On this basis, an enhanced Weibull-distribution-based formulation was developed to better capture the subsidence characteristics induced by caving mining in metal mines. The spatial uncertainty of rock-mass mechanical properties was then incorporated via reliability theory to provide a reliability-informed prediction of the subsidence range. Finally, the analytical predictions were validated by similarity simulation tests. The three approaches yield subsidence extents in the following ascending order: numerical simulation < similarity simulation test < reliability-based analysis. The discrepancy between theoretical predictions and test results ranges from 0.30% to less than 5%, demonstrating the robustness and credibility of the proposed method for subsidence-range delineation.

To reveal the energy evolution law of open-pit mine dumps under seismic conditions and establish a criterion for slope instability, the cusp catastrophe theory was combined with the energy theory in open-pit mine dumps. This led to the development of a theoretical instability model for dissipated energy catastrophe, using slope dissipated energy as state variable. The south dump of Dasuji Molybdenum Mine was taken as the engineering background. FLAC3D software was used to analyze the evolution patterns of dissipated energy of four slope sections in the south dump and analyze the mutation characteristics. Based on these findings, the stacking scheme of the dump was optimized. The results show that most of the characteristic values of the dissipated energy for the south dump slope section are below zero, and the slope is prone to instability under seismic loading. The simulation results are consistent with the field situations. According to the evolution characteristics of the dissipated energy of the slope, an optimization scheme of "slope reinforcement+stacking optimization+monitoring and early warning" is proposed and applied to the south dump. The numerical simulation analysis and field monitoring verification of the optimized scheme show that the anti-deformation ability and overall stability of the slope are significantly improved after taking the optimization measures. The research results can provide references for the preventing dump slope instability.

Frequent geological disasters occur on open-pit mine slopes, and traditional monitoring methods have limitations in real-time performance, coverage density and intelligent early warning. Based on the research achievements in the field of slope safety monitoring and early warning, the existing deficiencies and key problems to be solved urgently at present were summarized. Internet of Things, cloud computing, big data and artificial intelligence technologies were integrated, the space-air-ground-subsurface multi-dimensional and multi-source collaborative sensing network was constructed, the intelligent monitoring and early warning platform for open-pit mine slopes was developed, and intelligent diagnosis and trend prediction of slope stability were carried out. Through a graded early warning mechanism and a visual decision-making system, accurate risk identification and emergency linkage were realized. Practical results show that the intelligent monitoring and early warning platform for open-pit mine slopes significantly improves the proactive perception and advanced early warning capabilities of slope risks, and provides technical support for the intrinsic safety and intelligent mine construction of open-pit mines.

Aiming at the problems of significant strength damage of sandstone in cold regions under freeze-thaw action and the complex research process of traditional test methods, a machine learning-based prediction model for the strength damage of freeze-thawed sandstone was proposed. By means of literature research, 117 sets of experimental data on strength damage of sandstone after freeze-thaw cycels were selected as the data set. The longitudinal wave velocity, dry density, saturated density, number of cycles and freeze-thaw period were selected as the input characteristics of the model, and the strength loss rate was used as the output characteristics. Six machine learning models such as decision tree, random forest, support vector machine, XGBoost, extreme random tree and CatBoost were used to predict the strength damage of sandstone after freeze-thaw cycles, and R², MAE, MSE and RMSE were used to evaluate the performance of the model. The results show that the CatBoost model has the best performance in all evaluation indicators. Its R² on the test set exceeds 0.93, and the MAE value, MSE value and RMSE value are 0.028, 0.002 and 0.039, respectively, showing strong generalization ability and good prediction effect. Further, the Bayesian optimization algorithm was used to optimize the hyperparameters of the CatBoost model, and the number of iterations, the maximum depth of the tree and L2 regularization were determined as the key parameters affecting the prediction performance of the model. Eigenvalue weight analysis shows that the order of importance of each variable to the model contribution is : number of cycles>freeze-thaw period>dry density>saturated density>longitudinal wave velocity. The research results can provide effective prediction tools and method references for rock mechanics engineering practice in cold regions.

Aiming at the problem of pillar stability, acoustic emission (AE) tests of rock specimen failure, PFC simulation of pillar failure, and pillar stability monitoring and early warning research were carried out. AE tests of rock specimens under simple loading and incremental cyclic loading-unloading conditions and PFC simulation of pillar failure were carried out. The stress-AE evolution characteristics during pillar failure were analyzed, and four stages of pillar failure were proposed, namely initial incubation stage, low-speed incubation stage, accelerated incubation stage and failure stage. Based on the stress-AE evolution characteristics of pillar failure, the pillar failure instability criteria of increased stress-stable AE, stable stress-stable AE, reduced stress-stable AE, increased stress-increased AE and reduced stress-increased AE modes were proposed. Based on the pillar failure criteria, a staging monitoring and early warning method for pillar stability is established, and a pillar stability monitoring and early warning platform was developed. The staging monitoring and early warning method for pillar failure and the pillar stability monitoring and early warning platform show good performance in field engineering applications. After pillar 2-45^# enters the increased stress-increased AE stage, the mine issues a red warning. Longitudinal cracks appear in the pillar 39 days later, and overall failure occurs 90 days later. After pillar 2-105^# enters the increased stress-stable AE stage, the mine issues a yellow warning. Local spalling occurs in the middle of the pillar 38 days later. The research results are of great significance for quantitatively evaluating pillar stability and ensuring safe production in mines.

To investigate the impact of acidic mine water erosion on the mechanical properties and microscopic failure mechanisms of limestone, the evolution of porosity, mechanical characteristics, and acoustic emission (AE) parameters (event rate, dominant frequency, energy rate, and crack type) across varying erosion durations (0, 14, 28, 42, and 56 days) was examined through uniaxial compression and AE tests. The results indicate that during the mine water erosion process, the porosity of the limestone increases from 0.26% in the intact state to 9.13% after 56 days of erosion. Uniaxial compression tests reveal that the peak strength, peak strain, and elastic modulus of the limestone progressively decrease with prolonged erosion time; specifically, the peak strength of the specimens eroded for 56 days decreases by 29.41% compared to the un-eroded counterparts. Furthermore, both the AE event rate and energy rate increase as erosion time extended. During the deformation and failure process, the number of low-dominant-frequency AE signals progressively multiplied, whereas the high-dominant-frequency AE signals exhibits a declining trend. Additionally, the proportion of shear microcracks demonstrates a gradual decrease, while the proportion of tensile microcracks correspondingly increases from 30.69% in the intact state to 57.92% after 56 days of erosion. Consequently, mine water erosion induces a progressive increase in porosity and exacerbates the propagation of microcracks and pores, thereby precipitating a substantial deterioration in mechanical performance. These findings provide robust theoretical support and technical guidance for the safe and efficient extraction of non-ferrous metal resources in water-rich environments.

To investigate the influences of fissure dip angle and filling material on the rock mechanical properties, uniaxial compression tests were conducted on fissured sandstone specimens containing fractures with varying dip angles and filling materials. Digital Image Correlation (DIC) and Acoustic Emission (AE) techniques were employed to monitor the deformation and fracture processes. DIC was used to capture surface strain distribution and crack propagation morphology, and AE was utilized to monitor the crack evolution processes. The distribution characteristics of the RA-AF parameters were analyzed. The results indicate that the filling material prolongs the elastic deformation stage of the fissured sandstone and enhances its brittleness. The effect on the compressive strength diminishes as the inclination angle of the fissures increasing. The elastic modulus of the unfilled specimens is positively correlated with the dip angle of the fissures, while the elastic modulus of the filled specimens is not affected by the dip angle of the fissures. After filling, the strain distribution of the specimens is more uniform, and the crack propagation path becomes concentrated. The unfilled sandstone specimens with a fissure dip angle of 0° to 15° exhibit wing-shaped tensile failure, while those with angles of 30° to 90° show wing-shaped shear failure. All filled specimens exhibit mixed tensile-shear failure. The AE analysis results show that the crack propagation in the unfilled specimens is consistent with the DIC results, while in the filled specimens, tensile cracks are the main type and shear cracks are secondary. The filling materials significantly alter the mechanical behaviors of fissured sandstone. The failure mode and crack evolution are jointly controlled by the filling state and the dip angle of the fissures. The research results provide a theoretical basis for the stability analysis of engineering involving filled-fissured rock masses.

To explore the damage distribution characteristics of rock mass caused by complex stress wave generated by blasting in soft and hard composite rock mass, a double-hole blasting model of composite rock mass composed of rock Ⅰ (relatively hard) and rock Ⅱ (relatively soft) was established based on LS-DYNA software. The damage law of rock under different initiation sequence and initiation delay time was discussed. The results show that in the composite rock mass, after the superposition of blasting stress waves, the stress waves in Rock Ⅰ override those in Rock Ⅱ and propagate further. The attenuation rate of effective stress in Rock Ⅰ is larger than that in Rock Ⅱ, resulting in the overall effective stress in Rock Ⅰ being smaller than that in Rock Ⅱ. The effective stress between the two blast holes in the composite rock mass decreases first and then increases, and the overall effective stress in Rock Ⅰ is always lower than that in Rock Ⅱ. The fractal dimension of rock decreases first and then increases with the increase of delay time. The fractal dimension of rock in Rock Ⅰ is larger than that in Rock Ⅱ when the blast hole is detonated first. The findings provide a reference significance for blasting construction in rock masses engineering under similar conditions.

To investigate the influence of Nano-SiO₂ (NS) on the performance of ultrafine cement and evaluate its application efficacy in grouted bolts, test groups with varying NS dosages were established. A series of tests, including fluidity, initial setting time, mechanical properties of the grouted body, SEM microstructure, and pullout performance, were systematically conducted. Furthermore, optical frequency domain reflectometry (OFDR) was employed to monitor the strain distribution during the pullout process. The results indicate that the incorporation of NS decreases the fluidity and initial setting time of the nano-composite grouting materials while accelerating the early hydration reaction rate. At an optimal NS dosage of 2%, the compressive and flexural strengths of the grouted body are maximized, and the microstructure becomes significantly denser. The pullout tests and OFDR fiber monitoring reveal that the ultimate bearing capacity of the nano-composite grouted bolt is elevated to 210 kN. Additionally, the load-displacement curve exhibits enhanced ductility and higher residual strength; concurrently, the strain distribution along the bolt rod is more uniform, with a reduction in abrupt local strain variations. These findings verify the feasibility and effectiveness of nano-composite grouting materials in improving anchoring performance, providing robust technical support for the optimization of anchoring systems in geotechnical engineering.

To investigate the combined effects of pre-oxidation and water immersion on the characteristics of coal oxidation combustion, a thermogravimetric analysis was performed on gas-coal samples subjected to various pre-oxidation temperatures and water immersion conditions. The characteristic temperature, activation energy and reaction rate of coal oxidation combustion under different conditions were analyzed, and the mechanism of the effects of pre-oxidation and water immersion on coal oxidation combustion was discussed. The results indicate that, compared to unoxidized raw coal, the characteristic temperatures of the combustion weight loss stage decreased by 2.8% and 0.2% at 150 ℃ and 240 ℃ pre-oxidation temperatures, respectively, while the activation energies decreased by 4.9% and 48.7%, respectively. Pre-oxidation increased the risk of coal spontaneous combustion, with higher pre-oxidation temperatures leading to a greater propensity for reignition. Furthermore, compared to pre-oxidized coal at 240 ℃, additional water immersion of this high-temperature pre-oxidized coal significantly lowered its oxidative combustion characteristic temperature and activation energy. The characteristic temperatures for the oxidation weight gain stage and combustion weight loss stage decreased by 65.2 ℃ and 16.3 ℃, respectively. The activation energy of the combustion mass loss stage decreases by 7.8 kJ·mol^-1, indicating an increased risk of coal spontaneous combustion. The combustion reaction rate of coal decreases after water immersion. The value of pre-exponential factor(lnA) for raw coal after water immersion is reduced by 6.3% compared with raw coal, while for coal samples pre-oxidized at 240 ℃ and then treated with water immersion, lnA is decreased by 60.4%. When coal bodies undergo high-temperature oxidation, direct water injection for cooling is not recommended. Instead, other fire prevention and suppression measures such as injecting low-temperature nitrogen or liquid carbon dioxide should be prioritized.

Aiming at the characteristics of many influencing factors of mine safety production, complex interaction relationship and fuzzy quantitative evaluation, an influencing factor analysis and risk evaluation model based on DEMATEL-ISM-CM was established. Firstly, a risk evaluation index system for mine safety was constructed from five dimensions: personnel, equipment, environment, management and technology. Then, the DEMATEL-ISM method was applied to identify key influencing factors, the multi-layer hierarchical structure diagram was drawn, and the index weights were calculated according to the centrality of the influencing factors. Finally, a lead-zinc mine in Hunan Province was selected as a case study to assess its mine safety risk level. The results show that the key factors affecting mine safety include engineering geological conditions, safety protection equipment, advanced mining technology, safety production investment and emergency management system, and the degree of mechanization and intelligent level of equipment are the fundamental causes. Based on the comprehensive evaluation cloud diagram model, the safety production risk of the mine was classified as low (level Ⅳ), which is consistent with engineering practice and confirms the reliability and applicability of the model. The multi-layer hierarchical structure diagram can clarify the transmission path of risk factors and provide theoretical guidance for the safety management of mining enterprises.

To explore the research hotspots and development trends in the field of mine ecological restoration, based on the literature data retrieved from Web of Science (WOS) and China National Knowledge Infrastructure (CNKI), 692 English literatures and 298 Chinese literatures were visually analyzed using software including VOSviewer, CiteSpace and SCImago Graphica. The differences among various mine ecological restoration philosophies and key restoration technologies were also discussed. The results show that the number of publications in the field of mine ecological restoration shows an overall upward trend. Cooperation among countries is frequent, and a research network has been formed with China as the primary core and European and American countries such as the United States, Australia and Spain as the secondary cores. Cooperation among international high-yield institutions is close, while connections among domestic high-yield institutions are lacking. Research hotspots focus on coal mine restoration, phytoremediation technology, soil heavy metal remediation, microbial mechanism research, restoration effect evaluation, and carbon neutrality target practice. In the future, it is necessary to further study the restoration technologies of basic mine ecological units dominated by soil, microorganisms and plants, promote the application of emerging technologies such as UAV aerial mapping and machine learning in model construction and effect evaluation, and explore the path of mine ecological restoration under the carbon neutrality goal. Mine ecological restoration research is currently in a period of explosive development. China should combine macro-monitoring with micro-research, apply cutting-edge technologies, promote interdisciplinary integration and cross-field cooperation, and continuously improve the research system of mine ecological restoration in China.

A self-oscillating pulsed jet nozzle can convert a continuous jet into a pulsed jet, which effectively enhances rock-breaking efficiency by inflicting periodic "water hammer" damage on the rock. As the core component for regulating jet morphology, the conventional linear structure of the nozzle oscillation cavity suffers from energy dissipation, thereby constraining jet performance. To address this, a study was conducted to investigate the influence of the cavity diameter ratio (the ratio of the oscillation cavity length L to the upper nozzle diameter d₁) on the pulsed jet performance within the external field, thereby identifying the optimal range for this ratio. From the perspective of flow field structure, the dynamic relationship between the internal low-velocity zone of the cavity and jet performance was analyzed, and Bezier curves were employed to optimize the wall profile of the oscillation cavity. Rock breaking and punching experiments using the self-oscillating pulsed jet nozzle were performed before and after the shape optimization of the oscillation cavity wall to comparatively verify the optimization effect of the oscillation cavity shape of the nozzle. The results indicate that when the cavity diameter ratio is between 5 and 6, the internal low-velocity zone of the oscillation cavity is minimized, yielding optimal jet performance in the external field. For the optimized nozzle, the average velocity and peak velocity of the external field exhibit increases of 16.99% and 16.74%, respectively. Furthermore, compared with the original nozzle, the diameter, depth, and volume of the punching holes generated by the pulsed jet impact on the rock are enlarged by 25.45%, 24.27%, and 18.32%, respectively. These findings demonstrate that the overall performance of the self-oscillating pulsed jet nozzle is effectively upgraded.

Current path planning algorithms for mine cars generally suffer from low search efficiency and excessively long planned paths when navigating complex mining terrain. Developing highly efficient and precise path planning methods has thus become a critical issue requiring urgent resolution. An innovative two-layer transportation path planning scheme was proposed. The upper layer employed the improved A^* algorithm to initially plan the paths between nodes, while the lower layer utilized the improved sparrow search algorithm (ISSA) for overall path optimization. This ensured the minimization of energy consumption and cost for the overall path, aiming to achieve efficient and precise mining transportation path planning. The results show that the two-layer transportation path planning scheme based on the improved A^* algorithm and ISSA not only realizes the minimization of path energy consumption, but also minimizes the path cost, effectively enhancing the efficiency and safety of path planning. In the path planning process, the proposed scheme by the research institute will not be affected by obstacles, there will be no situation of taking a detour, and it can reach the destination along the shortest path. It has excellent obstacle avoidance and shortest path planning capabilities. Moreover, in the three-dimensional topographic map of the mine with complex terrain, it can quickly solve the target function value with lower energy consumption and lower path cost. The shortest transportation distance obtained by the two-layer transportation path planning scheme based on the improved A^* algorithm and ISSA is only 3 125.36 m. The cargo damage cost, transportation cost, and carbon emission cost are 1 028.63 yuan, 3 968.57 yuan, and 335.18 yuan, respectively, and the transportation time is only 1 836.39 s. All these indicators are lower than those of the mine transportation path planning scheme based on the genetic-ant colony reinforcement learning algorithm.

To optimize the antenna layout for mine wireless communication systems, a 3D model of a rectangular roadway measuring 5 m in width and 3.4 m in height was constructed using the Shooting and Bouncing Ray tracing (SBR) method. A multi-scale analysis of power attenuation characteristics in the 0.9 GHz, 2.4 GHz, and 3.5 GHz frequency bands within roadways was conducted across transmission distance, longitudinal cross-section, and spatial distribution. The impact of antenna positioning on wireless transmission was also investigated. The results show that the 0.9 GHz frequency band exhibits superior transmission characteristics compared to the other two bands. The mean longitudinal cross-sectional power at different transmission distances is 6.60-9.17 dBm and 10.49-12.63 dBm higher than that for 2.4 GHz and 3.5 GHz, respectively. The optimum horizontal position for the antenna is within 0.01 to 0.1 m from the roadway wall. When the antenna was deployed flush against the wall (within 0.01 m of the wall), the spatial power distribution exhibites an asymmetric characteristic. The received power in the adjacent wall area on the same side as the transmitting antenna is 1 to 4 dBm higher than on the opposite side. A stable and strong reception signal can be obtained when the height difference between the transmitting and receiving antennas is less than 0.5 m. The research findings may serve as a reference for optimizing base station placement and antenna layout within roadways, thereby facilitating the development and construction of intelligent communication systems for mining operations.

The grades of gold, silver, copper, lead, zinc, sulfur and iron in a low-grade polymetallic sulfide ore in western Yunnan are 1.92 g/t, 41.31 g/t, 0.39%, 1.20%, 0.42%, 9.54% and 34.92% respectively, and the content of harmful element As is 0.22%. The low-grade polymetallic sulfide ore has low grade of valuable elements, complex occurrence state, many kinds of minerals, uneven dissemination size, and difficult comprehensive recovery. The genetic characteristics of the ore, including the composition and relative content of main minerals, the dissemination relationship of the main minerals, grain size and liberation characteristics, as well as the occurrence states of gold, silver, copper, lead, zinc, sulfur and iron, were systematically investigated and determined using chemical analysis and chemical phase analysis. Based on this, the principle process of "copper-lead mixed flotation, copper-lead separation, zinc-sulfur mixed flotation, zinc-sulfur separation, and low-intensity magnetic separation for iron" was proposed. The results of laboratory process verification test show that under the condition of grinding fineness of -0.074 mm accounting for 90%, the concentrates are obtained as follows, copper concentrate with a copper grade of 21.19%, gold grade of 52.40 g/t, silver grade of 558 g/t, and copper recovery of 74.50%; lead concentrate with a lead grade of 74.66%, gold grade of 24.85 g/t, silver grade of 1 730 g/t, and lead recovery of 82.54%; zinc concentrate with a zinc grade of 46.27% and zinc recovery of 76.88%; sulfur concentrate with a sulfur grade of 45.54% and sulfur recovery of 81.91%; as well as magnetite concentrate with an iron grade of 63.47% and iron recovery of 36.87%.

A copper-sulfur ore processing plant in Guangdong employed a "high-alkali copper extraction-weak-acid sulfur extraction" process and reagent system. To address the problems of high on-site alkali consumption, low flotation efficiency, and elevated safety and environmental risks, experimental studies were conducted on ore properties and mineral processing techniques. This led to the identification of a "low-alkali, acid-free" process scheme and based on the ore characteristics, the development of a tailored, low-alkali reagent system for the green and efficient separation of copper-sulfur. Results indicate that a scheme employing B18 to collect copper minerals and CD-S2 to partially replace lime for sulfur suppression, with copper sulfate replacing sulfuric acid for activation, and butyl xanthate for sulfur floation, is effective. The closed-circuit test achieved a copper concentrate with Cu grade of 20.84% and Cu recovery of 88.11%, along with a comprehensive sulfur concentrate with S grade of 46.12% and S recovery of 94.68%. Compared to the "high-alkali-weak-acid" process, the "low-alkali-acid-free" process can increase the copper grade and recovery in copper concentrate by 2.59 percentage points and 1.94 percentage points respectively, while maintaining comparable overall sulfur concentrate indicators. The pH of the roughing pulp in closed-circuit tests decreases from 11 to 8.5, achieving clean and efficient separation and recovery of copper and sulfur in a low-alkali-acid-free environment.

To address the low flotation separation efficiency of chalcopyrite and pyrite, a novel thiol collector (930 agent) was adopted in flotation tests. Its selective adsorption mechanism was revealed by Fourier transform infrared spectroscopy analysis, and its effectiveness was verified through mineral flotation tests. The test results show that the novel environment-friendly and high-efficiency collector 930 agent, obtained by functional group structure reconstruction based on thiol collectors, increases the copper recovery of concentrate by 12.27% and 4.77%, the sulfur recovery of concentrate by 13.84% and 1.99%, and raises the sulfur grade of sulfur concentrate by 3.37% and 3.00% respectively, compared with the traditional collectors ethyl xanthate and butyl xanthate. The use of the new 930 collector optimizes the selectivity of copper-sulfur separation, provides a novel agent scheme with high selectivity and environmental friendliness for sulfide ore flotation separation, and is of great significance for reducing smelting costs and alkaline wastewater discharge.

To investigate the effect of varying magnetization times on the reverse flotation of fine-grained hematite, water, reagents, and slurry were subjected to magnetization treatments of differing durations. By measuring the conductivity and surface tension of the solution, the viscosity of the solution and slurry, and the changes in infrared and Raman spectra of the mineral particle surfaces at different magnetization times, the mechanism by which magnetization time influences the reverse flotation of hematite was revealed. Results indicate that the magnetization effect is optimal at an 8-minute magnetization time. Magnetized water, starch and slurry can enhance hematite recovery rates by 2.3 percentage points, 4.16 percentage points and 3.84 percentage points respectively, whereas magnetized dodecyl amine reduces hematite recovery by 3.56 percentage points. Magnetization increases the solution's electrical conductivity, enhancing the solubility of reagents and the concentration of electrolytes within the solution. It also elevates viscosity, thereby strengthening the inhibitor's efficacy and preventing hematite particles from floating. Furthermore, it reduces the solution's surface tension, facilitating the adhesion of quartz to bubbles and improving the recovery rate in hematite reverse flotation. Infrared spectroscopy analysis indicates that magnetization influences the interaction between the reagent and the mineral surface, altering the amount of reagent adsorbed onto the mineral surface.

To effectively solve the problems of poor selectivity and only being suitable for separation in weakly alkaline environment of traditional cationic collectors used in reverse flotation desilication of phosphate, a novel high-efficiency cationic collector SDTQ suitable for separation in weakly acidic environment was developed. Flotation tests were carried out on a siliceous-magnesian phosphate from Guizhou Province using this collector. The results show that when pH=6 and the SDTQ dosage is 25 mg/L, the recovery of pure quartz mineral is close to 100%, while fluorapatite exhibits no obvious floatability. In the flotation of artificial mixed ore, good separation effect of fluorapatite and quartz is achieved at pH=6 with an SDTQ dosage of 100 mg/L. On this basis, using the magnesium-depleted phosphate concentrate pulp at pH=6 as the research object, the collector dosage condition test was carried out. The optimal SDTQ dosage is determined to be 1.1 kg/t. Under this collector dosage, open-circuit tests were carried out. The separation indexes of P₂O₅ grade 35.38%, P₂O₅ recovery 85.41% and acid-insoluble content 5.53% in phosphate concentrate are obtained. Finally, through the closed-circuit process of one roughing, one cleaning and one scavenging, favorable separation indexes are obtained, with P₂O₅ grade of 35.49%, P₂O₅ recovery of 90.31% and acid-insoluble content of 9.81% in phosphate concentrate. Compared with dodecylamine, SDTQ increases the P₂O₅ grade of phosphate concentrate by 2.05 percentage points and the recovery by 10.02 percentage points. The measurement results of Zeta potential and contact angle show that SDTQ is selectively adsorbed on the quartz surface through electrostatic interaction, and the enhanced hydrophobicity difference between quartz and fluorapatite is the key mechanism to achieve efficient desilication in phosphate reverse flotation. The test results of atomic force microscopy and Fourier transform infrared spectroscopy show that SDTQ collector acts on the quartz surface in the form of physical adsorption through the synergistic effect of quaternary ammonium cationic groups and long-chain alkyl groups. SDTQ collector can improve the grade of phosphate, reduce reagent cost, and has both economic and environmental advantages.

To investigate the motion patterns and separation mechanisms of different magnetic particles in a permanent magnet roller separator during mineral processing, a magnetic force calculation model was established based on the magnetic field gradient and particle specific magnetic susceptibility. The magnetic field distribution of the permanent magnet roller system was simulated using ANSYS Maxwell. The obtained magnetic field vector data were then imported into the EDEM simulation environment via its field management interface. Subsequently, secondary development was performed using the C++ API to extend EDEM's capabilities for simulating particle behavior under magnetic forces. Simulation results indicate that the distribution density of magnetic particles in high-velocity zones is significantly higher than that of intergrowth particles and non-magnetic particles. As particle size increases from 15 mm to 60 mm, the average and the minimum roll-off speeds of the particles show an increasing trend, while the maximum roll-off speed exhibits the opposite behavior. When the magnetic roller speed increases from 10 r/min to 50 r/min, the trajectory spacing among magnetic particles, intergrowth particles, and non-magnetic particles all increase. At a speed of 30 r/min, particle separation performance is optimal. Experimental validation of the coupled simulation method demonstrates that it can realistically simulate the magnetic particle separation process. The research findings provide crucial theoretical foundations and technical support for optimizing such mineral processing technologies.

Aiming at the problem of low separation accuracy when recovering copper and aluminum particles from lithium iron phosphate batteries by wind specific gravity separation method, heavy liquid separation was conducted on three samples: the copper-aluminum mixture obtained after crushing and screening of battery cells from a factory's battery crushing and sorting system, as well as the copper product and aluminum product obtained from air gravity separation. The results show that at a heavy liquid density of 2.95 g/cm³ and a solid-liquid ratio of 0.35 g/mL, the aluminum recovery rates of the copper-aluminum mixture vary with particle size. For particles >0.630 mm, the Al and Cu recovery rates reach 96.99% and 99.72%, respectively; for particles of 0.630-0.104 mm, the corresponding values are 97.62% and 90.02%. The recovery rates of aluminum and copper are 96.44% and 99.83%, respectively. The aluminum recovery rate of particles greater than 0.630 mm reaches 99.66%, and the copper recovery rate reaches 98.52%. The aluminum recovery rate for particles in the 0.630-0.125 mm size range reaches 90.60%, and the copper recovery rate reaches 96.46%. Copper and aluminum can be obtained from raw materials via heavy liquid separation, and separated from raw materials using the same method. The research results provide a basis for the subsequent separation of black powder and metal particles.

As an important industrial by-product produced in the process of coal-fired power generation, fly ash shows great potential in CO₂ mineralization. In order to solve the problem of low efficiency of direct mineralization of CO₂ by fly ash, N-methyldiethanolamine (MDEA)/diisopropanolamine (DIPA) mixed amine solution was used to absorb CO₂ to improve the subsequent CO₂ fixation efficiency. The effects of different MDEA/DIPA ratio, solid-liquid ratio, reaction temperature and reaction time on CO₂ absorption and mineralization efficiency were systematically analyzed. The results show that the performance of MDEA/DIPA mixed amine solution is better than that of monoamine solution. When the MDEA∶DIPA is 1∶3, the solid-liquid ratio is 270 g/L, the reaction temperature is 45 ℃, and the reaction time is not less than 30 min, the CO₂ loading is the highest, which is 1.66 mol/L, and the mineralization efficiency is 45.2%. The results of FTIR, XRD and TG analysis show that MDEA/DIPA mixed amine solution mainly contained , , protonated MDEA/DIPA and carbamate. Compared with the original fly ash sample, the content of CaCO₃ in the solid product increased significantly, and mainly existed in the form of calcite. MDEA/DIPA mixed amine solution and fly ash combine CO₂ absorption and mineralization, which provides a reference for CO₂ storage and fly ash waste treatment.