Extensive soft-rock floor heave in gob-side entry retaining considerably restricts the efficient and sustainable production of the mine. The mechanical capacities of roadway roof and floor strata are discussed through laboratory tests by taking the N2301 fully caving surface auxiliary transport gate road of the Ancient City Coal Mine in the Lu’an Mining Area of Shanxi Province as an engineering background. The stress distribution law of gob-side entry in mining the working surface was explored based on numerical simulation. After that, the mechanical mechanism of floor heave was studied through theoretical analysis. High lead abutment pressure and horizontal stress were superimposed in front of the working surface to cause soft-rock floor heave. The bulk weight of the high overburden was unevenly transmitted to the two sides because of the roof cantilever structure of entry retaining in the rear of the working face. The roadway floor produced an asymmetric sliding force, which caused the occurrence of floor heave. The control technology of floor heave combining the pressure relief of floor blasting and roof cutting was proposed taking account of the mechanism of floor heave. Then, the stress environment of the surrounding rock was improved by the deep hole blasting of the floor. Gob-side roof cutting was used to reduce impact of the bulk weight of the overburden on the surrounding rock deformation of the roadway. A test was conducted after verifying the control effect of blasting pressure relief on roadway floor heave through a similar simulation. Field tests indicated that the maximum floor heave was 168 mm at 250 m in the rear of the working surface, and floor heave was controlled. This study offers a more scientifically sound theoretical reference for controlling floor heave in gob-side entry retaining, which can significantly advance the sustainable development of gob-side entry retaining technology in coal mining.

Green mining plays a vital role in achieving environmentally friendly and ecologically sound mining practices. In domestic mining areas, the coal mining method is gradually transitioning from collapse mining to filling mining. Paste filling has been proven effective in controlling surface deformation, although the understanding of its underlying control mechanisms remains incomplete. This study focuses on the E1302 paste-filling working face at Shanxi Gaohe Energy Co., Ltd. and conducts a comprehensive investigation into the movement patterns of overlying strata in longwall fully mechanized mining with paste filling. Through mathematical analysis, a mechanical model for overburden movement in paste-filling faces is established, and the movement behavior of overburden is studied through numerical simulations. Field measurements are conducted to analyze the primary influencing factors of overburden movement, while surface subsidence monitoring is employed to analyze the subsidence characteristics of paste-filling faces. The research reveals that the deflection formula for the roof behind the paste-filling face follows a unitary quartic equation. The key factors influencing significant roof subsidence in filling faces include the filling step distance, filling body strength, and filling rate. Compared to traditional caving mining, filling mining exhibits reduced stress concentration, a smaller range of stress influence, and less deformation in the surrounding rock. The coefficient of gentle subsidence for the overlying rock in filling mining is approximately one-tenth of that in caving mining. The development of cracks in filling mining can be divided into three stages: initial crack propagation, crack recompaction, and stable maintenance of cracks. Notably, the progression of advanced cracks assumes a “sail-shaped” pattern, and the area of crack recompaction is located above the rear side of the excavation. Cracks behind the working face only appear in the basal roof rock layer. When the filling rate in longwall fully mechanized mining with paste filling exceeds 94%, the top plate of the filling working face remains intact but exhibits bending and sinking. The sinking of the top plate increases exponentially with the filling step distance, and approximately 80% of the filling body’s deformation occurs within 20 m after filling. Following backfilling mining, the stability period of the overlying rock is significantly shortened compared to caving mining, resulting in a relatively gentle movement without an active surface movement phase. After six months of backfilling, the overlying rock settles steadily and consistently. The subsidence coefficient for backfilling mining is 0.065, with a maximum surface subsidence of 215 mm. These findings highlight the successful control of surface subsidence. The research outcomes provide an effective theoretical foundation and research direction for predicting overburden movement and surface subsidence in paste-filling faces.

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.

Many problems exist in the layout of working surfaces in high-gas mines, such as the low efficiency of roadway excavation, difficulties in maintenance after excavation, and serious resource wastes due to difficulties in recovering coal pillars between roadways. Taking the project profile in the west wing mining area of Sihe Coal Mine as the background, this work proposed an optimization plan for the staggered-layer arrangement of roadways. The minimum retained size of the coal pillar was calculated through theoretical analysis, and the plastic failure and deformations of surrounding rocks under different coal pillar sizes and roadway layouts were compared based on finite difference numerical simulations. The reasonable retained size of the coal pillar was determined to be 45 m, and the roadway layout was determined according to the distribution of coal and rock strata in the mining field. The technical measures of base angle pressure relief blasting and strengthening support were proposed to ensure the safety and stability of surrounding rocks of roadways during the service period after the layout plan was optimized. Similar simulation tests were used to study the damage deformations and stress changes of the blasting pressure relief floor. On-site tests showed that the optimized roadway layout greatly improved the recovery rate of coal resources. In addition, surrounding rocks had good stability, and they could be simply repaired or serve the next working surface directly without being repaired. These research results provide a scientific basis and useful reference for similar projects.

This work focused on the serious coal compression under buildings, railways, and water bodies in central and eastern China; the wide range of rock formation damage during the collapse mining process; the high pressure of mines; and difficulties in controlling surface subsidence after mining. The E1302 working face of Shanxi Gaohe Energy was taken as the engineering background in the work. The mechanical properties of gangue paste-filling materials were studied through laboratory tests, and the critical conditions for bending and fracture of the coal seam roof were analyzed. Discrete-element numerical simulation software was used to study the fracturing process of the roof, and the reasonable filling rate to ensure roof stability was determined to be 95%. Meanwhile, overlying stratum movement and mine-pressure weakening law were studied through numerical simulations and field measurement. The results showed that fracture development during the mining process of thick-coal paste filling was divided into the advanced development, re-compaction, and steady-state maintenance of fractures. Fractures advanced in a “sail shape” and developed only in the main-roof rock strata after recompaction. The maximum subsidence angle of the working face was 87.13° after mining, with a subsidence factor of 0.034 and a maximum horizontal movement coefficient of 0.71. The advanced stress value was weakened by 40%, and the influenced area was reduced by 13%. Overlying stratum movement was controlled, and mine pressures were significantly weakened. The work can provide a scientific basis for green backfill mining, roadway support design, and backfill mining equipment selection.

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.