1. China University of Mining and Technology (Beijing), State Key Laboratory of Coal Resources and Safe Mining, Beijing, China and China University of Mining and Technology (Beijing), College of Geoscience and Survey Engineering, Beijing, China.
2. China University of Mining and Technology (Beijing), State Key Laboratory of Coal Resources and Safe Mining, Beijing, China and China University of Mining and Technology (Beijing), College of Geoscience and Survey Engineering, Beijing, China. (corresponding author)