1. Key Laboratory of Geological Hazards on Three Gorges Reservoir Area, Ministry of Education, China Three Gorges University, Yichang 443002, P. R. China
2. School of Civil Engineering, Wuhan University, Wuhan 430072, P. R. China. E-mail: jqh1972@aliyun.com
3. School of Civil Engineering and Architecture, Nanchang University, Nanchang 330031, P. R. China