1. Lecturer, School of Civil and Transportation Engineering, Hebei Univ. of Technology, Tianjin 300401, China.
2. Professor, School of Civil and Transportation Engineering, Hebei Univ. of Technology, Tianjin 300401, China; Researcher, State Key Laboratory of Coal Mine Disaster Dynamics and Control, Chongqing Univ., Chongqing 400045, China (corresponding author).