Detailed Analysis of the Cutoff Height in Composite Hard Rock Roofs Along Goaf Roadways

• Published in: Processes Vol. 13; no. 3; p. 838
• Main Authors: Wu, Jun, Bai, Dongdong, Zhang, Yong, Zhu, Qingwen, Liu, Peiyue, Chen, Qingyu, Zhang, Yuxuan
• Format: Journal Article
• Language: English
• Published: Basel MDPI AG 12.03.2025
• Subjects: Analysis; Building failures; China; Coal industry; Coal mines; Coal mining; Composite beams; Construction costs; Cutting; Deformation; Deterrence; Drilling; Fractures; Geology; Height; Mathematical models; Mineral industry; Mines and mineral resources; Mining industry; Numerical analysis; Roof failures; Roofing; Simulation; Simulation methods; Tensile stress; United States; Work face; United States; China
• ISSN: 2227-9717; 2227-9717
• DOI: 10.3390/pr13030838

To ensure lateral roadway retention in composite hard rock mining roofs, selecting a proper cutting height is crucial. If the cutting height is too low, the residual hard roof may experience secondary fractures under additional stress, which threatens roadway stability and safe mining production. Conversely, if the cutting height is too high, the overlying rock layers may bear uneven stress, increasing the risk of collapse. To conduct a detailed cutting height analysis for composite hard rock roof retention, the 12 1103 working face at the Qiuji Coal Mine was chosen as the research subject. Using the collapse characteristics of a goaf roof and the theory of composite beams, a lateral mechanical model of a goaf roof was constructed. By integrating the ultimate tensile stress theory and the Maxwell model, the optimal cutting height for a composite hard roof was derived. Using UDEC numerical simulation software, a model for lateral roadway retention was established to compare and analyze the roof collapse effects, vertical displacement, and vertical stress at different cutting heights. The results indicated that a cutting height of 7.8 m (with the bottom of the hole 0.48 m from the four gray layers) achieved the best cutting effect. Field engineering tests further validated the rationality of the calculated results. Using field surveys, the cutting height was adjusted from the original 9.35 m to 7.8 m for the 12 1103 working face. With a working face length of 946 m, this adjustment could save approximately 212,900 yuan in drilling construction costs and improve construction efficiency by 15%. This study provides a theoretical basis and practical reference for selecting cutting heights under similar geological conditions.