1. International Joint Research Laboratory of Henan Province for Underground Space Development and Disaster Prevention, Henan Polytechnic University, Jiaozuo 454003, P. R. China
2. School of Civil Engineering, Henan Polytechnic University, Jiaozuo 454003, P. R. China
3. School of Civil, Mining and Environmental Engineering, University of Wollongong, Wollongong, NSW 2522, Australia