1. State Key Laboratory of Coal Resources and Safe Mining; China University of Mining and Technology; Beijing 100083 China
2. College of Geoscience and Surveying Engineering; China University of Mining and Technology; Beijing 100083 China
3. Key Laboratory of Mineral Resources, Institute of Geology and Geophysics; Chinese Academy of Sciences; Beijing 100029 China
4. Mine Safety Technology Branch of China Coal Research Institute; Beijing 100013 China