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.