1. Department of Civil Engineering Xi'an Jiaotong University, Xianning West Road 28, 710049, Xi'an Shannxi, P. R. China
2. Key Lab. for the Exploitation of Southwestern Resources & the Environmental Hazard Control Engineering of Chinese Ministry of Education, Chongqing University, Chongqing, 400044, P. R. China
3. Department of Civil Engineering Xi'an Jiaotong University, Xianning West Road 28, Xi'an Shannxi, 710049, P. R. China
4. School of Civil Engineering, Xi'an University of architecture and technology, 13 Yanta Road, Xi'an Shannxi, 710055, P. R. China