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.

The width of the coal pillar is a key factor in the success of the gob-side entry driving (GED) technique. This paper, based on the 4,317 working face at Chengzhuang Coal Mine, reveals the stability mechanism of roadway surrounding rock during GED with coal pillars of different widths. Firstly, a main roof failure mechanical model was established using the “internal and external stress field” theory, and the range of the internal stress field was calculated to be 13.6–15.2 m, with the optimal coal pillar width being 10 m. Then, a FLAC^3D numerical model was developed and calibrated. Through simulation, the stress and plastic zone evolution characteristics of coal pillars with widths of 5 m, 10 m, 15 m, and 20 m were compared. The results show that a 5 m coal pillar has weak bearing capacity, is prone to plastic failure, and the surrounding rock stability is poor. A 10 m coal pillar exhibits a more uniform stress distribution, smaller plastic zone, and maintains a certain elastic region, with good bearing capacity and no significant stress concentration. It is the optimal design width, offering strong economic and safety advantages. In contrast, 15 m and 20 m coal pillars show significant stress concentration, threatening coal pillar stability and causing resource waste. Finally, a combined control technique of “hydraulic fracturing roof cutting + roof anchor cable + rib anchor cable” with specific parameters was proposed and successfully applied in the 4,317 tailgate. Field monitoring results showed that the surrounding rock deformation stabilized after 55 days, with a maximum deformation of 151 mm, indicating good control effectiveness.

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.

Due to the influence of high crustal stress, weak surrounding rock, and other factors, deep soft rock roadways are often in complex stress states. This study takes the III4104 roadway as the research object to reveal the deformation mechanisms of deep soft rock roadways, aiming to effectively address the support challenges faced by such roadways. Firstly, a field survey summarized the failure characteristics of deep soft rock roadway and analyzed the causes of failure. Secondly, a mechanical model of floor heave was established, and the maximum depth of floor damage was calculated. Subsequently, based on the UDEC Trigon method, a discrete element numerical model that meets engineering scale was constructed, and a correction method for model parameters was proposed. Through simulation research, the deformation characteristics of surrounding rock, displacement vector distribution, crack distribution, and plastic zone extent were explored. Finally, a combined control technology of “roof corner anchor cable + rib anchor cable + concrete inverted arch + floor anchor cable” was proposed, along with specific parameters, and successfully applied in the III4104 roadway. The application results showed that, after 50 days of monitoring, the surrounding rock deformation stabilized, with the overall deformation rate controlled within 5%, indicating good control performance. The research results provide technical assistance for the stable control of surrounding rock deformation in deep soft rock roadways.

Taking the gob-side entry retaining (GER) in the 28,051 panel of Xinzhuang Coal Mine as the engineering background, this study introduces the second invariant of deviatoric stress (J₂) as a quantitative indicator of surrounding rock failure. By constructing mechanical model, performing FLAC^3D numerical simulation, and conducting industrial experiment, the full-cycle failure evolution law of the surrounding rock and its control technology are systematically investigated. A mechanical model of the roadside filling body is established, from which the reasonable filling width beside the roadway is calculated to be 1.0 m. Simulation results indicate that during the early stage of GER, the J₂ of the surrounding rock exhibits a ring-shaped non-uniform distribution with peak values at a depth of 2.5 m in both the roof and the solid coal rib. In the middle stage, under strong mining disturbance, the J₂ peak shifts deeper to 4.5 m in the roof and 3.5 m in the coal rib. In the late stage, as the delayed working face distance increases, the peak value of J₂ show an increasing trend with gradually diminishing increments, stabilizing eventually. However, the peak value of J₂ at the solid coal side rib corner continues to rise. The J₂ distribution of filling body is approximately linear, with stress values increasing from the gob side to the roadway side, and the degree of stress concentration decreases with increasing delayed distance. Based on these findings, a support concept is proposed that requires anchor cables to penetrate through the J₂ peak zones of the solid coal rib and roof. This is integrated with high-density rock bolts and flexible cement slurry walls to form a comprehensive control technology for GER. Industrial practice demonstrates that the maximum roadway deformation is controlled within 294 mm, and the filling body deformation stabilizes around 90 mm, validating the effectiveness of the support design and achieving full-cycle stability control of the surrounding rock in GER.