1. Research Associate, Australian Research Council Centre of Excellence in Geotechnical Science and Engineering, Univ. of Newcastle, Callaghan, NSW 2308, Australia.
2. Research Associate, Australian Research Council Centre of Excellence in Geotechnical Science and Engineering, Univ. of Newcastle, Callaghan, NSW 2308, Australia (corresponding author).
3. Emeritus Professor, Australian Research Council Centre of Excellence in Geotechnical Science and Engineering, Univ. of Newcastle, Callaghan, NSW 2308, Australia.
4. Associate Professor, Australian Research Council Centre of Excellence in Geotechnical Science and Engineering, Univ. of Newcastle, Callaghan, NSW 2308, Australia.