1. School of Mines, Key Laboratory of Deep Coal Resource Mining, China University of Mining and Technology, Xuzhou, Jiangsu 221116, China
2. The State Key Laboratory of Coal Resources and Safe Mining, China University of Mining and Technology, Xuzhou, Jiangsu 221116, China
3. School of Geology and Mining Engineering, Xinjiang University, Urumqi, Xinjiang 830046, China
4. School of Civil, Mining and Environmental Engineering, University of Wollongong, Northfield, NSW 2500, Australia