1. State Key Laboratory of Coal Resources and Safe Mining, China University of Mining & Technology, No. 1 University Road, Xuzhou, Jiangsu 221116, China
2. School of Mines, China University of Mining & Technology, No. 1 University Road, Xuzhou, Jiangsu 221116, China
3. School of Minerals and Energy Resources Engineering, The University of New South Wales, Sydney 2052, Australia