1. Ph.D. Student, School of Civil Engineering and Mechanics, Lanzhou Univ., Lanzhou, Gansu 730000, PR China.
2. Professor, School of Civil Engineering and Mechanics, Lanzhou Univ., Lanzhou, Gansu 730000, PR China; Key Laboratory of Mechanics on Disaster and Environment in Western China, Ministry of Education of China, Lanzhou, Gansu 730000, PR China (corresponding author).
3. Graduate Student, School of Civil Engineering and Mechanics, Lanzhou Univ., Lanzhou, Gansu 730000, PR China.
4. Lecturer, School of Civil Engineering and Mechanics, Lanzhou Univ., Lanzhou, Gansu 730000, PR China; Key Laboratory of Mechanics on Disaster and Environment in Western China, Ministry of Education of China, Lanzhou, Gansu 730000, PR China.