To assess the thermal transformation process of common sulfide minerals in a nitrogen atmosphere, thermogravimetric analysis, X-ray diffraction, scanning electron microscopy, and thermogravimetric mass spectrometry are employed to define the influence of the pyrrhotite content in pyrite-pyrrhotite mixtures (mixed minerals). The results indicate that an increase in pyrrhotite content decreases the temperature of the maximum mass loss rate of mixed minerals and reduces its mass loss. The solid-phase transformation of the thermal decomposition of mixed minerals is accelerated because the apparent activation energy of pyrrhotite is lower than that of pyrite and mixed minerals. However, the pyrrhotite makes the mixed minerals easier to sinter and agglomerate, which reduces the total volatilization amount of the gas product, S₂; thus, the rate of mass loss decreases.

In the process of ion-adsorbed rare earth (RE) ore leaching and mining, the injected chemical agent and rare earth particles have a strong chemical reaction, resulting in changes in the structure of the rare earth, and thus affecting the macroscopic mechanical properties and permeability of soil. To investigate the evolution of the pore structure during the leaching process, indoor leaching simulation experiments were used to compare and analyze the changes of Zeta potential during the leaching process with different concentrations of leaching solution, the process of the gradual change of the strong and weak combined water layer was analyzed, and a nuclear magnetic resonance (NMR) instrument was used to obtain the structural parameters such as the porosity, T₂ spectrum and pore radius to analyze the evolution law of microscopic pore structure. The experimental results show that the deionized (DI) water leaching process has less effect on the pore structure of the ore body, and the pore structure inside the ore body evolves gradually from small and medium pore size pores to large pore size pores, while the pore structure of the ore body changes more during the leaching process of the MgSO₄ leaching solution. In the initial leaching stage, the number of minimal pores (0–0.24 μm) and small pores (0.24–0.65 μm) of the ore body decreases rapidly, and the number of large pores (1.6–10 μm) increases. In the effective leaching stage, the number of minimal pores (0–0.24 μm), small pores (0.24–0.65 μm) and medium pores (0.65–1.6 μm) increases, while the number of large pores (1.6–10 μm) and mega pores (greater than 10 μm) decreases. At the end of leaching stage, the pore size evolves from medium pores (0.65–1.6 μm) and small pore (0.24–0.65 μm) to large pores (1.6–10 μm). Both chemical replacement reaction and solution percolation can induce changes in the pore structure of the ore body, and the influence of the chemical replacement reaction is higher than that of percolation in the leaching process. The evolution of pore structure during ion exchange is caused by the difference of ionic strength in leaching solution. RE ore particles are adsorbed or released to the solid phase, and the migration of particles leads to changes in the interface properties of RE particles, which affects the pore structural changes.

During in situ leaching of ionic rare earth ore, the pore structure of the orebody changes due to the chemical replacement reaction between the leaching agent and the rare earth ore. To explore the influence of leaching agents on the pore structure of ionic rare earth ore during the leaching process, magnesium sulfate solutions with different concentrations and pH are used as leaching agents in this paper. An experimental method of indoor simulated column leaching, a Zetaprobe potential analyzer, and an NM-60 rock microstructure analyzer to measure parameters, including surface zeta potential, T2 map, and the pore structure of rare-earth ore particles, were used to analyze the influence law of magnesium sulfate solution on the pore structure of ionic rare earth ore. The result proves that pure H₂O leaching has little effect on the surface Zeta potential and the internal pore structure of the ore particles. In the leaching process of magnesium sulfate solutions with different concentrations, the absolute value of Zeta potential decreases, and the internal pore structure evolves from medium, large, and extra-large to small pores. In the leaching process of magnesium sulfate solutions with different pH, the absolute value of Zeta potential decreases and then increases slightly with the end of the ion exchange reaction. The internal pore structure generally shows a decrease in the number of small and extra-large pores and an increase in the number of medium and large pores. According to the analysis, the concentration and pH of the leaching agent cause the change of thickness of the electric double layer of the fine particles in the orebody, break the balance of interaction force between soil particles, and result in the evolution of a micropore structure of orebody during leaching.

As an important substitute for ammonium-free leaching, magnesium sulfate is applied as a leaching agent for the mining of ion-adsorbed REE (rare earth element) deposits. Upon deriving the equation regulating the leaching kinetics on the basis of the REE “shrinking core model” during the leaching process of magnesium sulfate, we conducted leaching experiments of natural particle-sized REE deposits by applying magnesium sulfate with concentrations of 1%, 2%, 3% and 4%. Hence, the leaching efficiencies and mass transfer rates were obtained. The results show that the hybrid control equation $\frac{\mathsf{\mu }\mathsf{\delta }}{{\mathrm{D}}_1}\mathsf{\alpha }+\frac{3\mathsf{\mu }\mathrm{r}}{2{\mathrm{D}}_2}\left[1-\frac{2}{3}{\mathsf{\alpha }-\left(1-\mathsf{\alpha }\right)}^{\frac{2}{3}}\right]=\frac{3{\mathrm{C}}_0\mathrm{M}}{\mathsf{\rho }\mathrm{r}}$ is applicable for describing the leaching process when the concentration of magnesium sulfate is 1%; when the concentrations reach 2%, 3% and 4%, the external diffusion control equation $\mathsf{\alpha }=\mathrm{k}\mathrm{t}$ is appropriate to describe the leaching processes. The leaching efficiency of REE deposits reaches over 90%, specifically, 94.65%, 97.24% and 97.98%, when the concentration of magnesium sulfate is 2%, 3% and 4%, respectively. The maximum mass transfer rate appears when the concentration of magnesium sulfate is 4%, and the leaching time is reduced by 1.96 times compared to 1% concentration of magnesium sulfate. The results provide a favorable theoretical basis for the green and efficient extraction of ion-adsorbed REEs.

The ionic rare earth (RE) ore body undergoes particle transport and pore structure change during the leaching process, resulting in "uneven percolation, preferential channel, leaching blind area," and other problems, leading to structural changes in the ore body, low leaching efficiency, and waste of resources. The unsaturated infiltration process is also the key stage that causes these problems. The initial pore structure evolution of the ore body plays a decisive role in the permeability coefficient of the ore body, and the direct influencing factor of the permeability coefficient is the distribution of the pore radius. We carried out research through indoor simulated leaching, the filter paper method for determining matrix suction, and nuclear magnetic resonance (NMR) testing. An ionic rare earth ore soil-water characteristic curve within a large matrix suction range was obtained by the filter paper method. With the increase in volumetric water content, the matrix suction presents a sharp downward trend. When the volumetric water content is less than 20%, this rule is particularly obvious. With the increase in matrix suction, the thickness of the adsorbed water film on the particle surface and pore radius show a decreasing power function trend. Under percolation, the porosity of an ionic rare earth ore sample tends to increase linearly with the increase in volumetric water content during the process from non-saturation to saturation; the porosity of a saturated ore sample after seepage expanded by 17.5 times compared to that of an unsaturated ore sample before seepage. The change rule of the internal microstructure of the ore sample is reflected in the gradual disappearance of micro pores and the gradual formation of small, medium, large, and mega pores, which shows a gradual increase trend. In the pore radius distribution, the more large and medium pores, the larger the permeability coefficient; the more micro and small pores, the smaller the permeability coefficient. For some ore bodies with poor permeability, the ore body is infiltrated with clear water under small water pressure before leaching with a leaching solution, which can improve the permeability of the ore body, effectively improve the efficiency of rare earth leaching, and increase the economic benefits.

Rockburst present substantial hazards in both deep underground construction and shallow depths, underscoring the critical need for accurate prediction methods. This study addressed this need by collecting and analyzing 69 real datasets of rockburst occurring within a 500 m burial depth, which posed challenges due to the dataset's multi-categorized, unbalanced, and small nature. Through a rigorous comparison and screening process involving 11 machine learning algorithms and optimization with KMeansSMOKE oversampling, the Random Forest algorithm emerged as the most optimal choice. Efficient adjustment of hyper parameter was achieved using the Optuna framework. The resulting KMSORF model, which integrates KMeansSMOKE, Optuna, and Random Forest, demonstrated superior performance compared to mainstream models such as Gradient Boosting (GB), Extreme Gradient Boosting (XBG), and Extra Trees (ET). Application of the model in a tungsten mine and tunnel project showcased its ability to accurately forecast rockburst levels, thereby providing valuable insights for risk management in underground construction. Overall, this study contributes to the advancement of safety measures in underground construction by offering an effective predictive model for rockburst occurrences.