Due to its excellent effect of surface subsidence reduction, the overburden-separation grouting (OSG) technology has been widely applied to green mining. However, OSG changes the mine pressure, and the resultant gas emission in the stope remains unclear. Therefore, with the 22301 working face of Tunlan Coal Mine as an example, the overburden deformation and stress distribution in the absence and presence of OSG were studied through numerical simulation and on-site tests. Furthermore, the gas emission law in the stope was contrastingly analyzed. The following results were obtained. With the rise of grouting pressure (GP), the subsidence of strata above the separation layer decreases while that below the separation layer increases; the heave displacement of floor strata below the coal seam gradually decreases. OSG significantly changes the geometric shape and range of the overburden stress relief zone. As the GP rises, the gas enrichment area moves downward continuously and shrinks spatially. Horizontally, the ranges of the stress relief zone and the free space in the goaf shrink, while the range and compaction degree of the compaction area gradually grow. After OSG, the total amount of gas emission in the working face falls by 52.2%.

In recent years, the integrity of the gas pipeline in the coal-gas co-mining subsidence area has become a critical problem, restricting the safe and efficient mining of coal resources. This paper establishes a theoretical model for the safety prediction of gas pipelines in mining subsidence areas based on elastic free theory, constructs a 3D model of pipe-sand soil by using ABAQUS simulation software (2021), analyzes the characteristics of ground surface and pipeline settlement combined with the measured data on-site, and reveals the temporal and spatial evolution law of the pipeline load and deformation under the condition of diagonal intersections of the pipeline and high-strength mining working face. The results show that during the mining cycle, the pipe and the sandy soil body experienced the stage of cooperative deformation, the stage of increasing non-cooperative deformation, and the stage of weakening non-cooperative deformation; the pipe body is most vulnerable to yield failure in the circumferential direction of 180°, 45°, 225°, and 0°; the relative deformation rate of the pipe experienced a slow and rapid increase in the stage, and tends to flatten out when the advancement length is about 1.5–2 times the distance at the taken cross-section. The study’s results are conducive to accurately predicting the pipe failure orientation under high-intensity mining conditions in coal seams, improving the diagnostic efficiency of pipes, and optimizing the advancement speed of the working face.

Aiming at the problem of the low reuse rate of mine water due to the high content of heavy metals in mine water, in this research, the microcharacterization means of EDX, XRD, BET, SEM, and FT-IR were used to characterize the nonstick coal in a mine in western China. The effects of solid–liquid ratio, solution pH, solution temperature, adsorption time, and initial concentration of the solution on the adsorption of Fe(II) by the nonstick coal were analyzed. The adsorption performance of nonstick coal on adsorbed Fe(II) was analyzed under different influencing factors. The results showed that the adsorption capacity and unit removal rate of the coal samples gradually decreased with the increase in the solid–liquid ratio; the adsorption amount increased with the increase in pH in an “S” shape, and the adsorption effect was better in the range of pH = 5~7; and the adsorption amount increased linearly with the temperature. The quasi-secondary kinetic model and Langmuir model could fit the adsorption kinetic curve and isothermal adsorption curve better, which indicated that the adsorption of Fe(II) by the nonstick coal was dominated by the chemical adsorption of the monomolecular layer. The quantitative analysis of the FT-IR results showed that the adsorption of Fe(II) was mainly by complexation with -OH detached from the coal samples to produce precipitation.

In recent years, controlling the integrity of shallow-buried natural gas pipelines within surface subsidence zones caused by high-intensity underground longwall mining in the Daniudi Gas Field of China’s Ordos Basin has emerged as a critical challenge impacting both mine planning and the safe, efficient co-exploitation of coal and deep natural gas resources. This study included field measurements and an analysis of surface subsidence data from high-intensity longwall mining operations at the Xiaobaodang No. 2 Coal Mine, revealing characteristic ground movement patterns under intensive extraction conditions. The subsidence basin was systematically divided into pipeline hazard zones using three key deformation indicators: horizontal strain, tilt, and curvature. Through ABAQUS-based 3D numerical modeling of coupled pipeline–coal seam mining systems, this research elucidated the spatiotemporal evolution of pipeline Von Mises stress under varying mining parameters, including working face advance rates, mining thicknesses, and pipeline orientation angles relative to the advance direction. The simulations further uncovered non-synchronous deformation behavior between the pipeline and its surrounding sand and soil, identifying two distinct evolutionary phases and three characteristic response patterns. Based on these findings, targeted pipeline integrity preservation measures were developed, with numerical validation demonstrating that maintaining advance rates below 10 m/d, restricting mining heights to under 2.5 m within the 260 m pre-mining influence zone, and where geotechnically feasible, the maximum stress of the pipeline laid perpendicular to the propulsion direction (90°) can be controlled below 480 MPa, and the separation amount between the pipe and the sand and soil can be controlled below 8.69 mm, which can effectively reduce the interference caused by mining. These results provide significant engineering guidance for optimizing longwall mining parameters while ensuring the structural integrity of shallow-buried pipelines in high-intensity extraction environments.

There are a large number of abandoned or casing-damaged oil/gas wells in the western mining areas of China. Under the influence of mining-induced stress, the methane leaked from the oil and gas wells will be transported through fracture within the coal pillar to the longwall working face, which will seriously threaten the safe mining of coal resources. There is no mandatory standard for the practice of coal pillars in coal and gas wells in coal/gas overlapping areas, and the problems of oversized coal pillars and waste of coal resources have occurred during the implementation. In this study, through finite element numerical simulation, three different sizes of protective coal pillars are modeled in the background of Shuangma Coal Mine. The impacts of different heights and widths of protective coal pillars on the evolution of stresses and the diffusion process of leaked methane are explored, and the spatial and temporal migration law of leaked methane under multi-field coupling is revealed. The results show that under mining-induced stress, the size of the protective coal pillar has a significant effect on the stress distribution and methane transport law. Compared with the 130 m coal pillar, the peak stress of the 150 m coal pillar decreased by 6.7%, and the peak stress of the 180 m coal pillar decreased by 9%. At 150 m and 180 m widths, the permeability difference between the two sides is only 1 mD, and the diffusion ranges are similar. From the stress distribution and gas diffusion law, it is shown that the effect achieved by 150 m and 180 m coal pillars is similar. This work is of great significance for the reasonable remaining protective coal pillars for oil/gas wells penetrating longwall mining areas, as well as the prevention and control of disasters caused by leaked methane from wells.