Study on the exhalation characteristics of radon from high-temperature rocks and the main controlling factors
摘要
Radon in goaf mainly comes from the exhalation of radon from the overlying rock body of the coal seam within the range of high-temperature influence, and it has become an effective means to guarantee the safety of coal mines by using the radon concentration on the surface of the overlying rock structure as an auxiliary indicator for predicting coal fire disasters. This paper summarizes the radon exhalation characteristics of four typical rocks in different studies for comparative analysis and summarizes the main controlling factors of radon exhalation in rocks by combining the gray correlation analysis method. The study’s results demonstrate that there is a significant correlation between the radon exhalation characteristics of the rocks and the temperature, and the radon exhalation rates of both limestone and phyllite increase gradually with the increase in the temperature, while the temperature threshold for the phase change of the radon exhalation rate of granite is 400 °C, and that of the radon exhalation rate of sandstone is 500 °C. Influenced by their own lithological differences, the four rocks showed different radon exhalation characteristics after heat treatment, with smaller radon exhalation rates in limestone and sandstone, and larger radon exhalation rates in granite and phyllite, in which the radon exhalation rate of granite reached 9.26 Bq m−2 h. The pore volume of micropores (< 0.1 µm) plays an essential role in the radon exhalation capacity, which is directly related to the fractal dimension of micropore structure in the heated rocks. The study’s findings can be used to identify coal fires.