1. Associate Professor, Dept. of Civil and Construction Engineering, National Taiwan Univ. of Science and Technology, 43, Sec. 4, Keelung Rd., Taipei 106, Taiwan (corresponding author).
2. Lecturer, Faculty of Civil and Water Resources Engineering, Bahir Dar Univ., P.O. Box 26, Bahir Dar, Ethiopia.
3. Lecturer, Dept. of Soil Mechanics and Foundations, Univ. of Technology and Education, Ho Chi Minh City, Vietnam.