1. Professor, College of Civil Engineering, Changsha Univ. of Science and Technology, Changsha 410114, PR China.
2. Ph.D. Candidate, College of Civil Engineering, Changsha Univ. of Science and Technology, Changsha 410114, PR China.
3. Assistant Professor, College of Civil Engineering, Hunan Univ., Changsha 410082, PR China; Key Laboratory of Building Safety and Energy Efficiency, Ministry of Education, Hunan Univ., Changsha 410082, PR China; State Key Laboratory of Geomechanics and Geotechnical Engineering, Institute of Rock and Soil Mechanics, Chinese Academy of Sciences, Wuhan 430071, China (corresponding author).