1. State Key Laboratory of Coal and CBM Co-mining, Jincheng 048012, China
2. School of Earth Resources, China University of Geosciences (Wuhan), Wuhan 430074, China
3. School of Resources and Safety Engineering, Chongqing University, Chongqing 400044, China
4. School of Mining Technology, Inner Mongolia University of Technology, Hohhot 010051, China