1. Professor of Civil Engineering and Research Director, Centre for Geomechanics and Railway Engineering, Faculty of Engineering, Univ. of Wollongong, Wollongong City, NSW 2522, Australia (corresponding author).
2. Ph.D. Candidate, Centre for Geomechanics and Railway Engineering, Faculty of Engineering, Univ. of Wollongong, Wollongong City, NSW 2522, Australia.
3. Research Fellow, Centre for Geomechanics and Railway Engineering, Faculty of Engineering, Univ. of Wollongong, Wollongong City, NSW 2522, Australia.