1. School of Civil Engineering, Central South Univ., Changsha, Hunan 410075, China; and Postdoctoral Research Centre, Guizhou Transportation Planning Survey and Design Academe, Guiyang, Guizhou 550001, China (corresponding author).
2. National Centre for Groundwater Research and Training, Univ. of Queensland, Brisbane, Queensland 4072, Australia.
3. School of Civil Engineering, Central South Univ., Changsha, Hunan 410075, China.