Study on the evolution law of failure depth of large mining height and ultra-wide working surface

Advancements in coal mining technology and sophisticated equipment have popularized large-scale mining with broad working faces. This study uses the 6306 ultra-wide working face of Jincheng Sihe Coal Mine as a case to establish a mechanical model of the bottom plate through theoretical analysis, field measurements, and numerical simulations. These methods address water outburst issues caused by high and wide working faces. The research systematically examines changes in the coal seam floor's displacement and stress fields during mining. A double-end water leak measurement device and peephole were employed to assess floor damage extent. Both quantitative and qualitative analyses were conducted to understand the dynamic evolution of destruction in large-scale mining with high and wide working faces, providing technical specifications for water control in constrained water and high-intensity coal mining environments. The results show that the maximum damage depth of the coal seam floor relates to peak advance support pressure and not just the coal wall's damage area. Field measurements using a drilling peep and leak detection equipment found the maximum damage depth of the test surface to be 19.63 m. Mining forces greatly impact the rock mass near the coal seam, increasing new floor cracks as the working face progresses. The measured maximum damage depth of 20.25 m aligns with theoretical values. Additionally, as the working face advances, a "stress arch" forms in the coal seam floor, significantly affecting the aquifer at its peak mining effect. After a certain distance, the pressure water guide becomes stable, and the bottom plate's vertical displacement increases, causing the pressure guide water belt's top interface to move upward and decrease pore water pressure. The research results can provide a theoretical basis for the prevention and control of water damage on the bottom plate of adjacent mines.