1. Assistant Professor, National Engineering Laboratory of Highway Maintenance Technology and Dept. of Traffic and Transportation Engineering, Changsha Univ. of Science and Technology, Changsha 410082, PR China.
2. Professor, Institute of Geotechnical Engineering, Hunan Univ., Changsha 410082, PR China.
3. Assistant Research Fellow, College of Civil Engineering, Hunan Univ., Changsha 410082, PR China (corresponding author).