Surface-based radon detection to identify spontaneous combustion areas in small abandoned coal mine gobs: Case study of a small coal mine in China

In China, small coal mines refer to non-state-run coal mines with an annual production of less than 300,000 tons. The mining recovery rate of these small Chinese coal mines is low, and large amounts of coal remain in the gob. The mining seams of small coal mines are shallow, which induces extensive fissures between the gob and ground and provides easy pathways for air leakage. Consequently, long-term air leakage and oxygen supplies can result in spontaneous coal combustion in the gob, forming fire areas for many years. Determination of spontaneous combustion areas in the gob of small coal mines is difficult because fire sources are hidden underground and the geological data and roadway layout are poorly documented. Surface-based radon detection provides a fast, accurate, and low-cost method to identify spontaneous combustion areas in the gob of small coal mines. This study focuses on a small abandoned coal mine in Shanxi Province, China, using surface-based radon detection. Three abnormal temperature areas (A, B, C) and a potential abnormal temperature area (D) were identified. Drilling was subsequently performed to measure the temperature distribution in these areas. The results show that spontaneous combustion areas in small abandoned coal mine gobs can be successfully identified.