Methane is one of the most important gases leading to the earth’s air pollution. Ventilation air methane(VAM) is an important part of the gas discharged into the atmosphere. The volume concentration of methane is generally less than 0.5% in coal mines. Recycling low concentration is facing challenges. To explore the law of low concentration methane enrichment, the enrichment tower for methane was designed and manufactured. The experiment was divided into two types - free diffusion and weak eddy enrichment, and eight kinds of low concentration gas experimental program. Under free diffusion conditions, the maximum methane concentration of the top (middle) tower is 0.64% (0.53%). In the condition of weak eddy field, the maximum methane concentration is 0.67% (0.69%) in the top (middle) tower. The effect of methane enrichment in the weak eddy field is obvious. Methane enrichment method under the eddy current field can greatly increase methane enrichment efficiency and achieve the goal of CMM (coal mine methane) power generation.

Gas extraction is an important measure for coal mine gas disaster control. Its effect is closely correlated to the drilling depth. The existing methods usually determine the drilling depth by manually counting the number of drill pipes, and the number of drill pipes can be automatically counted by object detection and real-time tracking algorithms. An improved object detection model was proposed for the problem of the poor performance of the object detection algorithm due to such interference factors as bright light, low illuminance and heavy dust and mist in coal mines. In terms of data augmentation, the ACE dehazing algorithm is introduced to improve image quality. In order to solve the problem of leak detection caused by the irregular shape that appears due to the interference of bright light, the deformable convolution DCNv2 module was integrated in the C2f module to make the sampling points of the convolution kernel diffuse irregularly, so as to fully extract the shape features of the drill pipe and then improve the detection rate of the model. For the problem of too low confidence of the model in detecting drill pipes due to uneven illumination, the attention paid by the model to the features of the drill pipe could be improved by embedding the SimAM non-parametric attention mechanism module in the backbone network, which can further improve the confidence of the drill pipe. For the problem of low average category detection accuracy caused by the changeable environment of the underground drilling site, the dynamic head was used to improve the ability of the model to extract the features of the drill pipe in scale, space, and channel, and improve the average category detection accuracy of the drill pipe. To address the issue of diverse angle differences between predicted and real boxes, CIoU loss function is replaced with the SIoU loss function. Finally, the improved detection algorithm was verified with the homemade drill pipe dataset. The experimental results showed that: the improved model effectively alleviated the problem of partial leak detection of the original network for scenes such as heavy dust and mist and uneven illumination; the recall rate increased by 4.9%; the mean average precision was improved by 5.3%. At the same time, it maintains a high real-time performance (the FPS is 117), providing the basis of the drill pipe detection model for the application of real-time tracking of the number of drill pipes.

Aiming at the roof control challenges of gob‐side entry retaining in fully mechanized top‐coal caving faces, traditional concrete‐filled steel tube (CFST) support technology exhibits limitations such as slow strength development and complex construction equipment. This study, based on the 1311 fully mechanized caving face in Shanxi Runhong Coal Mine, proposes a gob‐side entry retaining technology integrating roof cutting for pressure relief with support by grouted steel tubes. Through physical experiments, numerical simulations, and field tests, the mechanical properties of sulphoaluminate cement‐based backfill and grouted steel tube structures were analyzed. The results indicate that the sulphoaluminate cement‐based slurry with a water‐cement ratio of 0.4 exhibits remarkable early‐strength characteristics, achieving compressive strengths of 30.85 and 31.26 MPa at 1 and 28 days, respectively. The support system attains the 28‐day bearing capacity of traditional CFST within 24 h, effectively resolving the timeliness inadequacy of gob‐side support. Increasing the steel tube wall thickness enhances the bearing capacity more significantly than material strength improvement, with notable stress concentration and bending deformation observed at the middle region during loading. These findings provide a theoretical basis for support parameter optimization. Field applications demonstrate that this technology ensures surrounding rock stability while offering advantages such as simplified construction and reduced labor costs. This study provides theoretical support for the development of gob‐side entry retaining technology and offers practical guidance for its application in fully mechanized caving faces.

Gas disasters pose a significant constraint on the safe development of coal mines. Focusing on the problem of gas over-limits in the upper corner of a hard roof, this study takes the I010206 working face of Kuangou Coal Mine as a case study and proposes a high-level borehole gas extraction method. Initially, FLAC3D was employed to analyze the development pattern of the “three zones” in the overlying strata of the working face. The results revealed that the height of the fractured zone in the I010206 working face is approximately in the range of 30–90 m. Subsequently, COMSOL was utilized to elaborate on the effective extraction radius of boreholes. The influence laws of factors such as extraction time and borehole arrangement on the extraction effect were analyzed, and an optimized borehole-layout plan for high-level borehole gas extraction was put forward. Furthermore, based on the above-mentioned analysis, FLUENT was used to establish a borehole gas extraction model to study the gas extraction effect of high-position boreholes arranged in the fractured zone. The research demonstrated that the triangular-pyramid-type borehole layout is reasonable and effective. In addition, the optimal vertical height for high-level drilling was found to be 28–32 m from the roof, and the optimal horizontal distance is 10–15 m from the model boundary. These findings are expected to offer technical references and guidance for gas control in the upper corners of hard roofs.

The coal mining process is often accompanied by periodic disturbance of the surrounding rock mass around the coal mining face. Therefore, it is of great theoretical and engineering value to investigate the damage pattern of bituminous coal under cyclic loading and unloading conditions and analyze its damage precursors. The experiments of uniaxial multistage cyclic loading and unloading of bituminous coal were carried out, and the loading and unloading response ratios were extracted using the elastic modulus variation to describe the damage characteristics and damage precursors of bituminous coal. Based on the accumulated acoustic emission ringing counts, the response ratios were defined, and the internal damage evolution characteristics and damage laws during the damage of bituminous coal were analyzed. The CT scan images of the internal structure of the coal sample before and after the experiment were used to analyze the damage characteristics of the coal sample and the influence of the number of simulation units on the results using the inverse modeling simulation analysis method. The research shows that the response ratio of bituminous coal under uniaxial cyclic loading has three stages of variation, and it is characterized by periodic “W”-type variation at each level of stress. In addition, the inverse modeling and simulation can better characterize the damage evolution of the coal specimen.