High gassy mines have low recovery rates of coal resources in the stoping of high-seam coal resources in addition to difficulties in the gas control of the working face and gas accumulation in the goaf and upper corner. Pillar-free gob-side entry-retaining technology was combined with the high-pumping roadway for gas control in the goaf based on the W1319 working face in the Gaohe Coal Mine. Theoretical analysis and numerical simulation were used to derive the width of the reserved coal pillar in the high-gas pillar-free working face and the horizon of the high-pumping roadway. The location of the high-pumping roadway was determined in combination with the on-site investigation. Numerical simulations were used to compare the plastic failures and deformations of surrounding rocks in the cases of non-roof-cutting, roof cutting, and reinforced roof cutting. It could solve large and uncontrolled surrounding rock deformations of the gob-side entry-retaining technology and return airway in the stoping of the working face. The plasticizing zone and surrounding rock deformation of the gob-side entry-retaining technology were weakened in the case of roof cutting. However, the surrounding-rock failure of the return airway was not significantly weakened. The plastic failure of surrounding rocks in the gob-side entry-retaining technology and return airway weakened after the roof-cutting pressure relief and grouting reinforcement, and deformations reduced greatly. The surrounding-rock control measures of roof-cutting pressure relief and grouting reinforcement were determined. The gob-side entry-retaining technology had small surrounding-rock deformations in the advance of the working face, which verified the reliability of numerical simulations and the feasibility of the technical measures of roof-cutting pressure relief and grouting reinforcement. Meanwhile, the high-pumping roadway had a good drainage effect to avoid gas accumulation in the goaf, which provides a reference for the mining of high-seam coal resources.

Multiple roadways are opened to solve the difficulties in gas control in the high seam working face of high gassy mines, resulting in a large width of coal pillars between roadway groups. Moreover, recovering coal pillars is challenging during stoping, which causes serious resource waste. While the size of coal pillars is optimized, the reasonable horizon layout of roadway groups is performed to ensure a fine recovery rate of coal resources, mine safety, and efficient production. Theoretical analysis was applied to calculate the stress distribution of surrounding rocks around coal pillars based on the engineering practice of the W2302 working face in the Sihe Coal Mine. The MathCAD software Prime 2.0 combined with the on-site measured stress was used to draw the stress distribution under different coal pillar widths, which can derive the stress distribution data of the floor. The vertical stress concentration factors tended to be consistent at 10 m below the coal pillars and about 12 m from the centerline of coal pillars under different coal pillar widths, this area was suitable for the layout of floor rock roadways with a stress concentration factor of about 1. Numerical simulations were used to compare the stress distributions of the roadway floor and the deformation features of surrounding rocks under different coal pillar widths. The coal pillar width was finally determined to be 45 m, which optimized the size of coal pillars. The return air roadways were arranged at 9.8 m below the coal seam combined with the strata distribution on-site. According to the industrial test on-site, the return air roadways were available during the service period, which showed reliable theoretical analysis and simulation results. A reasonable horizon layout of return air roadways can provide a scientific basis and reference for similar projects.

The proportion of the coal and rock masses in different areas of surrounding rocks is quite different when a large-section coal roadway is excavated in gently inclined soft coal seams. Different creep failure occurs in coal and rock masses under high stress, which results in uneven deformations of roadways and difficulties in maintenance. This work studied the belt grooves of the 2103 working face in the lower coal group of the Wulihou Coal Mine. Theoretical analysis and measured geomechanical evaluation were used to analyze the failure causes of the surrounding rocks of the roadway. The failure law of large-section roadways in the gently inclined soft coal seams was studied using finite-difference numerical simulation software. Combined with the results of mathematical analysis, surrounding rocks were divided into regions. Surrounding-rock control schemes for different areas, such as grouting reinforcement, strengthening support, and pressure-relief grooving, were proposed separately and verified by numerical simulations. Strengthening the supports could reduce the deformations of area I, and pressure-relief grooving could control the deformations of area IV. The roadway and support system formed an anchored composite supporting body after grouting reinforcement, which greatly improved the bearing capacity and controlled the deformations of surrounding rocks. The fine on-site application effect and the improved non-symmetrical deformation verified the theoretical analysis, numerical simulations, and control technologies. The results provide a scientific basis and useful reference for similar projects.

Coal bio-gasification is one in situ coal gasification technology that utilizes the digestion of organic components in coal by methanogenic bacteria. It is not only an effective technology to enhance the recoverable reserves of coalbed methane, but also an important technical method to promote clean coal utilization. Relevant laboratory researches have confirmed the technical feasibility of anthracite bio-gasification. However, in the complex environment of coal bed, whether in situ gas can be yield with methanogenic bacteria needs to be verified by in situ experiments. In this study, a vertical well and a horizontal well were used in Qinshui basin to perform field experiments to confirm the technical industrial feasibility. The concentration of Cl⁻ ion and number changes of Methanogen spp. were used to trace nutrition diffusion. Gas production changes and coalbed biome evolution were used to analyze technical implementation results. The trace data and biome evolution identified that: (1) The development of Methanoculleus spp. has a significant positive correlation with culture medium diffusion; (2) the structure of coalbed microbial community was significantly changed with the injection of nutrition, and the newly constructed methanogenic community was more suitable for fermentation of coal; and (3) the evolution of dominant microflora has further enhanced bio-gasification of coal. Gas production data showed that the gasification of coal lasted 635 and 799 days and yielded 74,817 m³ and 251,754 m³ coalbed methane in Z-159 and Z-7H wells, respectively. One nutrition injection in coalbed achieved an average of 717 days of continuous gas production in experimental wells. Results confirmed that coalbed methane enhancement with bio-gasification of coal is a potential technology to achieve the productivity improvement of coalbed methane wells. And the findings of this study can help to further understand the mechanism of in situ coal bio-gasification and provide theoretical support for the development of biomining of coal.

Environmental perception is crucial for achieving autonomous driving of auxiliary haulage vehicles in underground coal mines. The complex underground environment and working conditions, such as dust pollution, uneven lighting, and sensor data abnormalities, pose challenges to multimodal fusion perception. These challenges include: (1) the lack of a reasonable and effective method for evaluating the reliability of different modality data; (2) the absence of in-depth fusion methods for different modality data that can handle sensor failures; and (3) the lack of a multimodal dataset for underground coal mines to support model training. To address these issues, this paper proposes a coal mine underground BEV multiscale-enhanced fusion perception model based on dynamic weight adjustment. First, camera and LiDAR modality data are uniformly mapped into BEV space to achieve multimodal feature alignment. Then, a Mixture of Experts-Fuzzy Logic Inference Module (MoE-FLIM) is designed to infer weights for different modality data based on BEV feature dimensions. Next, a Pyramid Multiscale Feature Enhancement and Fusion Module (PMS-FFEM) is introduced to ensure the model’s perception performance in the event of sensor data abnormalities. Lastly, a multimodal dataset for underground coal mines is constructed to provide support for model training and testing in real-world scenarios. Experimental results show that the proposed method demonstrates good accuracy and stability in object-detection tasks in coal mine underground environments, maintaining high detection performance, especially in typical complex scenes such as low light and dust fog.

Paste backfill strength exhibits obvious time-dependent growth, which directly determines the supporting effect and parameter design in longwall backfilling mining. To optimize key parameters for roof stability and surface protection, this study carried out laboratory tests, numerical simulations, and field validation on the E1302-B working face in Gaohe Coal Mine. Results show that the strength of paste backfill increases logarithmically with curing age. The optimal backfilling step distance is 2.4 m, the recommended final cured strength is 4.01 MPa with significant marginal effects, and the backfilling ratio should be no less than 92% to meet Grade-I surface protection requirements. Field applications demonstrate that under these parameters, roof deformation is controllable without fracture, and all surface deformation indexes are within 50% of the standard limits. This work provides a reliable method and practical guidance for parameter optimization in longwall paste backfilling mining.