1. Ph.D. Candidate, School of Civil and Resource Engineering, The Univ. of Western Australia, Perth, Australia. E-mail: helinski@civil.uwa.edu.au
2. Professor, School of Civil and Resource Engineering, The Univ. of Western Australia, 35 Sterling Highway, Crawley, Perth, Australia (corresponding author). E-mail: fahey@civil.uwa.edu.au
3. Professor, Australian Center for Geomechanics, The Univ. of Western Australia, Perth, Australia. E-mail:andyf@acg.uwa.edu.au