1. China University of Mining and Technology-Beijing, State Key Laboratory of Coal Resources and Safe Mining, Beijing, China. (corresponding author)
2. Beijing Dadi Hi-Tech Geological Exploration Company Limited, Beijing, China.
3. China University of Mining and Technology, School of Geoscience and Surveying Engineering, Beijing, China.
4. China University of Mining and Technology, School of Geoscience and Surveying Engineering, Beijing, China. .