1. Postgraduate Student, School of Engineering, Deakin Univ., Pigdons Rd., Geelong, Victoria 3217, Australia (corresponding author).
2. Lecturer, School of Engineering, Deakin Univ., Victoria 3217, Australia.
3. Postgraduate Student, School of Engineering, Deakin Univ., Victoria 3217, Australia.
4. Professor, Centre for Geotechnical and Materials Modelling, Univ. of Newcastle, New South Wales 2308, Australia.