1. Key Laboratory of Coal Methane and Fire Control, Ministry of Education, China University of Mining and Technology, Xuzhou 221116, China
2. School of Safety Engineering, China University of Mining and Technology, Xuzhou 221116, China
3. Shandong Engineering Research Center of Mine Gas Disaster Prevention, Qingdao, Shandong 266500, China
4. The First Exploration Team of Shandong Coalfield Geologic Bureau, Qingdao, Shandong 266500, China