1. Associate Professor, Geotechnical Research Unit, Dept. of Civil Engineering, Faculty of Engineering, Chulalongkorn Univ., Phaya Thai Rd., Pathumwan, Bangkok 10330, Thailand (corresponding author).
2. Ph.D. Research Fellow, Geotechnical Research Unit, Dept. of Civil Engineering, Faculty of Engineering, Chulalongkorn Univ., Bangkok 10330, Thailand.