1. College of Mining and Safety Engineering, Shandong University of Science and Technology, Qingdao 266590, China
2. State Key Laboratory of Mine Disaster Prevention and Control, Shandong University of Science and Technology, Qingdao 266590, China
3. National Demonstration Center for Experimental Mining Engineering Education, Shandong University of Science and Technology, Qingdao 266590, China
4. Department of Civil and Environmental Engineering, Stanford University, Stanford 94306, California, United States