1. a Key Laboratory of Coalbed Methane Resources and Reservoir Formation Process, Ministry of Education, China University of Mining and Technology, Xuzhou, Jiangsu 221008, China
2. b School of Resources and Geosciences, China University of Mining and Technology, Xuzhou, Jiangsu 221116, China
3. c National Engineering Research Center of Coal Mine Water Hazard Controlling, Suzhou University, Suzhou, Anhui 234000, China
4. d School of Resources and Environmental Engineering, Hefei University of Technology, Hefei, Anhui 230000, China