1. Key Laboratory of Road & Bridge and Underground Engineering of Gansu Province
2. National and Provincial Joint Engineering Laboratory of Road & Bridge Disaster Prevention and Control, Lanzhou Jiaotong Univ., Lanzhou 730070, CN (Corresponding author), email: libolzjtu@hotmail.com
3. School of Civil Engineering, Lanzhou Jiaotong Univ., Lanzhou, Gansu 730070, CN