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.