1. College of Safety and Environmental Engineering, Shandong University of Science and Technology, Qingdao, Shandong 266590, China
2. Key Laboratory of Ministry of Education for Mine Disaster Prevention and Control, Shandong University of Science and Technology, Qingdao, Shandong 266590, China
3. North China Geological Exploration Bureau of Tianjin, Tianjin 300170, China