To address coal pillar instability, the study focuses on the 3⁻¹ coal seam coal pillar at Nanliang Coal Mine. It analyzes the bending deformation energy of the main roof and the pre-yield elastic energy of the coal pillar’s elastic zone through theoretical analysis, similar simulation, and field measurements. The formula for the bending elastic energy of the main roof is derived by establishing the mechanical model of the roadway’s main roof near the goaf side. Based on the side abutment stress distribution of the coal pillar, the calculation of the pre-yield elastic energy distribution along the width direction of the coal pillar’s elastic zone is conducted, leading to the derivation of the instability energy criterion for the coal pillar. The range analysis method is used to analyze the influencing factors and distribution patterns of the bending elastic energy of the main roof and the pre-yield elastic energy of the coal pillar’s elastic zone. Findings indicate that the main roof’s tensile strength is the primary factor influencing bending elastic energy. Higher tensile strength of the main roof, and smaller load, larger thickness and elastic modulus on the overlying strata, lead to higher bending elastic energy in the main roof. The internal friction angle, width of the coal pillar, and elastic modulus of the coal seam notably impact the pre-yield elastic energy of the coal pillar’s elastic zone. A larger internal friction angle and coal pillar width, along with a smaller elastic modulus, result in higher pre-yield elastic energy in the coal pillar’s elastic zone. Using the working face of 3⁻¹ coal seam in Nanliang Coal Mine as the engineering context, the study calculates the minimum coal pillar width required for stability. Physical simulations and field monitoring demonstrate that with a 9 m—wide coal pillar, there is no apparent deformation or failure in the surrounding rock of the roadway, indicating good internal rock stability.

Shallow coal seam mining makes the evolution form of mining fissures in rock and soil layers diversified, which leads to the easy penetration of mining fissures as the main channel of water, sand inrush, and air leakage. In order to reveal the co-evolution mechanism of broken rock beam structure and mining fissures in key strata, taking Hanjiawan Coal Mine as the research background, the relationship between mining fissures and rock beam structure, fissure activation period, propagation characteristics, and connectivity of working face was studied by means of field observation, physical similarity simulation, and theoretical derivation. The research shows that the fracture structure of key strata in shallow coal seam mining mainly includes hinged rock beam and step rock beam structures. Through the analysis of the rock beam structure, we found that the types of mining fissures in the overlying strata of key strata were up and down I-I and I-II mining fissures, and the heights of fissure development were 44.38 m and 98.35 m, respectively. The key block rotation made the mining fissures undergo five dynamic activation processes. The calculation formula of the fissure activation cycle was established, and the rock breaking angle, mining fracture lag distance, and fissure penetration discriminant were obtained and verified by field measurement results.

To study the deformation and failure mechanisms of soft rock mining roadways, the 1506 return airway of Anyang Coal Mine is taken as the engineering background. Based on limit analysis theory, a failure model based on a rigid slider system is constructed to assess the failure of the soft rock surrounding a roadway. The formulas for calculating the self-weight power of the slider in the velocity discontinuity line of the rock surrounding the roadway, the work power of the surrounding rock pressure, and the energy dissipation rate of the velocity discontinuity line are derived, and the upper limit objective function of the velocity discontinuity line height is obtained. The failure characteristics and fracture evolution process of the surrounding rock under different mining stresses are analyzed by means of physical similarity simulations. The simulation results show that shear failure occurs first on the roadway side due to stress concentration. The fissures expand along the bottom angle of the roadway to the blind support area and the low-intensity support area. The cracks weaken the support strength of the angled anchor cable and bolt in the roadway shoulder. Under the action of roof pressure, the status of the rock mass inside and outside the shear slip zone changes from static to dynamic. This causes deformation and failure of the roadway roof, side, and floor.

In order to address the issue of slow excavation speed caused by various factors affecting the stability of the roof in the excavation face and the unreasonable distance of the unsupported roof, a mechanical model of the roof in the excavation face area is established. This model is based on the superposition method in the material mechanics. The immediate roof deflection curve equation and the maximum unsupported roof distance discriminant formula of the heading head are derived. The allowable deflection is used as the discriminant method of the maximum unsupported roof distance. The calculation method of the key parameters in the formula is obtained and compared with the existing maximum unsupported roof distance calculation formula. Using the single-variable sensitivity analysis method and the bivariate interaction analysis method, we determine the key factors affecting the deformation of the roof in the excavation face and their interaction relationships. The results indicate that among the 10 factors affecting the deformation of the roof in the temporary support area of the excavation face, there are 3 key factors. Under unchanged geological and mechanical conditions, the deformation of the roof primarily depends on the length of the temporary support area and the temporary support load. To provide a practical example, we calculate the maximum unsupported roof distance of 30304 tailgate in the Yanghuopan Coal Mine to be 3.4 m. Numerical simulation and field monitoring results confirm that the deformation of the roof in the excavation face is minimal, and the stability of the rock is good.

Shallow coal seam mining results in the formation of various bearing structures in key strata, leading to varying degrees of surface subsidence and severe disruption to the surface ecological environment. To investigate the coupled evolution characteristics of key strata fracture-bearing structures and surface subsidence in shallow coal seam mining, with a focus on the 1–2 coal seam mining at Longhua Coal Mine in northern Shaanxi as the research background, this study employed physical similarity simulation to establish the correlation between key strata fracture-bearing structures and surface subsidence. The study also utilized theoretical calculations to develop models for the trapezoidal hinged arch structure and the coupling between key strata-bearing structures and surface subsidence. Mechanical properties of bearing structures and the coupled evolution characteristics of surface subsidence were examined, and the scientific validity of the models was verified through field monitoring. The research reveals that the inclined section of the working face in shallow coal seam mining forms a trapezoidal hinged arch structure, where stress transmission actually resembles an arch shape. Based on the fracture characteristics of rock strata, this structure can be categorized into three types: a full-trapezoidal hinged arch structure, a semi-trapezoidal hinged arch structure, and a trapezoidal-like hinged arch structure. A mechanical calculation model for the trapezoidal hinged arch structure was constructed, and the mechanical calculation formula for this structure was derived based on mechanical equilibrium conditions. Using a masonry beam mechanical model, the formula for calculating the subsidence of key blocks in the key strata fracture was obtained. Based on the “masonry beam” mechanical model, a formula was derived to calculate the subsidence of key blocks in fractured key strata. The relationship between key strata-bearing structures and surface subsidence curves was analyzed, leading to the development of a calculation model for both. This model reveals the coupled evolution between rock movement and surface subsidence. Field measurements indicate a maximum surface subsidence of 1.93 m, with a subsidence coefficient of 0.65, showing that the surface helps suppress and reduce the overall subsidence.

Given the potential for dynamic load-induced support crushing that may occur during mining under an interval goaf through an isolated coal pillar (ICP) in shallow closely spaced coal seams, this paper systematically explored this issue through a case study of the 30,103 working face at the Nanliang Coal Mine. We employed a combined approach of similarity simulations, theoretical analyses, numerical simulations, and field measurements to investigate the catastrophic failure mechanisms and prevention strategies for dynamic pressure-related hazards encountered when mining a lower coal seam that passes through an ICP. The findings indicated that the synchronous cutting instability of the interlayer effective bearing stratum (IEBS) and double-arch bridge structure of the ICP roof were the primary causes of dynamic load-induced support crushing at the working face. A mechanical model was developed to characterize the IEBS instability during mining under an interval goaf. The sources and transmission pathways of dynamic mining pressure during mining passing through the ICP were clarified. The linked instability of the double-arch bridge structure of the ICP roof was induced by IEBS failure. The UDEC numerical model was utilized to elucidate the instability of the IEBS during mining in the lower coal seam and to analyze the vertical stress distribution patterns in the floor rock strata of the interval goaf. A comprehensive prevention and control strategy for roof dynamic pressure, which includes pre-releasing concentrated stress in the ICP, strengthening the support strength of the working face, and accelerating the advancement speed was proposed. The effectiveness of this prevention and control strategy was validated through actually monitoring the characteristics of mining pressure data from the 30,103 working face following pressure relief. The findings provide valuable insights for rock stratum control of shallow and closely spaced coal seam mining under similar conditions.