1. School of Mines, Key Laboratory of Deep Coal Resource, Ministry of Education of China, China University of Mining & Technology, Xuzhou, Jiangsu 221116, People's Republic of China
2. The State Key Laboratory of Coal Resources and Safe Mining, China University of Mining & Technology, Xuzhou, Jiangsu 221116, People's Republic of China
3. School of Civil, Environmental and Mining Engineering, The University of Adelaide, South Australia, 5005, Australia