Roadways driven along the floor of thick coal seams, while retaining the top coal, form “thick coal seam floor roadways.” These large-section roadways feature a composite coal-rock roof and weak coal ribs, leading to low overall strength and poor stability of the surrounding rock. Significant deformation and “necking” often occur, accompanied by roof falls and rib spalling, which are exacerbated under high stress or adverse geology, threatening mine safety and production. In this study, the 2201 haulage gateway in Yingpanhao Coal Mine is investigated to address surrounding rock control in such deep roadways. Using field investigation, theoretical analysis, numerical simulation, and similar simulation tests, the failure mechanisms of ribs and roofs are analyzed. Rib failure is characterized by tensile fracture in the shallow zone, splitting failure in the medium-depth zone, and incomplete conjugate shear in the deep zone. Corresponding mechanical models are established, and a method for calculating total rib failure depth—combining tensile/splitting and shear failure depths—is proposed, along with a bolt length design formula. Based on this, a synergistic roof-and-rib support technology is developed. The failure mechanism and optimal support scheme are validated through simulation tests and successfully applied in the field, demonstrating satisfactory performance. The findings provide a valuable reference for support design in similar mining roadways.

The goaf ground pressure monitoring and early warning system (GGPMEW) is crucial for ensuring the safety of mining production. The use of the GGPMEW with a higher safety integrity level (SIL) will increase the production cost of the mine when the stability of the goaf is good, while if the stability of the goaf is poor, using the GGPMEW with a lower SIL will increase the risk of mining accidents. In order to evaluate whether the capability of the GGPMEW can meet the demand, the theory of safety integrity is introduced to evaluate the GGPMEW. Two methods for classifying the stability levels of the goaf are presented. Based on the As Low As Reasonable Practical (ALARP) principle, a matching model is established between the stability grades of goafs and the safety integrity levels of the GGPMEW. This model facilitates the determination of the optimal safety integrity levels of GGPMEW across varying risk grades of goafs. Finally, a case study of the Second Mining Area of Baiyinnuoer Lead-Zinc Mine of China Nonferrous Metal Mining Group is conducted to analyze the stability of goafs and the safety integrity of the GGPMEW. The analysis identifies three goafs with significant unsafe conditions and proposes corresponding engineering recommendations to address these issues.

To address the large deformation failure of coal pillar ribs in gob-side roadways under the geological conditions of extra-thick coal seams with hard roofs, their mechanical instability mechanism was systematically revealed through comprehensive theoretical analysis, numerical simulation, and field measurements, and an innovative coordinated control system was developed accordingly.Theoretical investigations identified a coupled disaster-inducing mechanism combining intensive dynamic loading effects from periodic roof fracturing with high-stress gradients in extra-thick coal seams, inducing significant stress migration in coal pillar ribs. Based on the dynamic evolution of the overlying strata structure and mining-induced stress field, a reinforcement system using constant-resistance energy-absorbing (NPR) anchor cables was established to enhance the stability of the coal pillar rib. Numerical simulations showed that the NPR anchor cable reinforcement reduced the coal pillar plastic-zone depth by 62.5%-78.6% and decreased the coal pillar stress peaks by 8.9%-17.5%. Field measurements further showed that, compared with the original support section, the peak coal stress in the reinforced section decreased by 20.9%-26.3%, rib bulging was reduced by approximately 52%, and the borehole fissure depth was reduced by about 50%. The developed coordinated control scheme provides a reference for coal pillar rib stability control in gob-side roadways under similar extra-thick coal seam and hard-roof conditions.