Assessment of the Current Status of Mining Activities at the Synclinal Bottom in the Nam Mau Underground Coal Mine, Vietnam

Abstract

Mining at synclinal bottoms represents a major technical challenge for underground coal mines in the Quang Ninh coal basin due to complex geological structures, high risks of water accumulation and gas concentration, and increased coal losses. This study presents a systematic assessment of mine opening schemes, field subdivision, mining methods, ventilation, transportation, and drainage applied at synclinal bottoms, using the Nam Mau underground coal mine as a representative case. The results indicate that the vertical misalignment of synclinal bottoms among coal seams is the primary constraint affecting mine development and production organization. The currently applied opening schemes, including the two-level opening system using crosscut roadways and raises, as well as the single-level opening by downward roadways, show distinct technical advantages and limitations. In particular, the two-level opening system provides superior ventilation and gravity-driven drainage conditions, thereby improving operational safety at synclinal bottoms, although it requires increased rock drivage and careful positioning to control coal losses. Field subdivision and longwall layout at synclinal bottoms are generally compatible with local structural characteristics; however, coal recovery rates and mechanization levels remain lower than international benchmarks. Comparative analysis with underground coal mines in China, Poland, Germany, and Australia highlights the need for optimized multi-level opening layouts, pre-drainage measures, and higher degrees of mechanization. The findings provide a scientific basis for optimizing synclinal bottom mining strategies in Vietnamese underground coal mines and support the transition toward safer and more efficient deep mining operations.