1. Associate Professor, State Key Laboratory of Geomechanics and Geotechnical Engineering, Institute of Rock and Soil Mechanics, Chinese Academy of Sciences, Wuhan 430071, China (corresponding author).
2. Professor, Dept. of Civil Engineering, National Univ. of Singapore, Singapore 117576, Singapore.
3. Professor, School of Environment and Civil Engineering, Wuhan Institute of Technology, Wuhan 430073, China.