1. Associate Professor, Key Laboratory of Ministry of Education for Mechanics on Western Disaster and Environment, School of Civil Engineering and Mechanics, Lanzhou Univ., Lanzhou 730000, China (corresponding author).
2. Graduate Student, Key Laboratory of Ministry of Education for Mechanics on Western Disaster and Environment, School of Civil Engineering and Mechanics, Lanzhou Univ., Lanzhou 730000, China.
3. Lecturer, Engineering and the Environment, Univ. of Southampton, Highfield, Southampton SO17 1BJ, UK.
4. Associate Professor, Key Laboratory of Ministry of Education for Mechanics on Western Disaster and Environment, School of Civil Engineering and Mechanics, Lanzhou Univ., Lanzhou 730000, China.