ABSTRACT
Coal is China's primary energy sources. With mining depth growing, rock temperature in coal mines is increasing. In 1980, the average mining depth of Chinese coal mines was 288 m, in 1995 reached 428 m, and at present mining depth is increasing at an average rate of 8-12 m annually. There are dozens of coal mines with mining depth over 1000 m. According to survey data from around the world, the global average geothermal gradient is about 3/100 m. According to China’s statistics, geothermal gradient in Chinese coal fields is 2-4/100 m. According to incomplete statistics, among China's state-owned key coal mines there are more than 50 coal mines with mining depth greater than 700 m, the deepest coal mines have depth of more than 1000 m. More than 80 coal mines suffers from different degrees of thermal hazard, of which 38 coal mines have working face of air temperature over 30 (Wang, Yang 2008). China is a country with the most coal mines of thermal hazard. 73.2% of the predicted reserves of coal is underground deeper than 1000 m. With increase of mining depth, heat hazard is increasingly prominent, and became one of major disasters in coal mines.
