1. College of Geology and Environment, Xi’an University of Science and Technology, Xi’an 710054, China
2. Key Laboratory of Coal Resources Exploration and Comprehensive Utilization, Ministry of Natural Resources, Xi’an 710021, China
3. State Key Laboratory of Eco-Hydraulics in Northwest Arid Region, Institute of Water Resources and Hydro-Electric Engineering, Xi’an University of Technology, Xi’an 710048, China
4. Coal Geology Bureau of Ningxia Hui Autonomous Region, Yinchuan 750002, China