基金Supported by the National Natural Science Foundation of China (41172138) the Special Fund Project of Jiangxi Energy Bureau (20100730) Acknowledgments The authors wish to thank Professor Tang Xiuyi from Anhui University of Science and Technology for his constructive advice. The authors also express their gratitude to the technical personnel from Jiangxi Exploration Institute of Coalfield Geology, Jiangxi Coal Group Corporation, for their kind help.