1. Research Fellow, Underground Technology and Rock Engineering Program, Protective Technology Research Center and School of Civil and Environmental Engineering, Nanyang Technological Univ., Singapore 639798, Singapore (corresponding author).
2. Professor of Rock Mechanics and Tunneling, Swiss Federal Institute of Technology Lausanne (EPFL), Rock Mechanics Laboratory (LMR), ENAC-ICARE-LMR, Station 18, CH-1015 Lausanne, Switzerland.
3. Associate Professor, Underground Technology and Rock Engineering Program, Protective Technology Research Center and School of Civil and Environmental Engineering, Nanyang Technological Univ., Singapore 639798, Singapore.
4. Tritech Consultants Pte Ltd, 10 Changi North Street 1, #01-03, Expression Technology Center, Singapore 498826, Singapore.