1. Professor, ChengNan College, Changsha Univ. of Science and Technology, Changsha, Hunan 410076, China.
2. Powerchina Zhongnan Engineering Corporation Limited, Construction and Traffic Engineering Division, Changsha, Hunan 410014, China (corresponding author).
3. Professor, Changsha Univ. of Science and Technology, Changsha, Hunan 410076, China.