1. Department of Geological Sciences; University of Alabama; Tuscaloosa AL 35406
2. College of Mechanics and Materials, Hohai University; Jiangsu Province 211100 China
3. State Key Laboratory of Hydrology-Water Resources and Hydraulic Engineering, College of Mechanics and Materials; Hohai University; Fuchengxi Road 8, Nanjing 210098 China
4. School of Resources and Environmental Engineering; Hefei University of Technology; Hefei 230009 China