1. Professor, Dept. of Civil Engineering, Dong-A Univ., 840 Hadan-dong, Saha-gu, Busan 604-714, Republic of Korea (corresponding author).
2. Researcher, Dept. of Civil Engineering, Dong-A Univ., 840 Hadan-dong, Saha-gu, Busan 604-714, Republic of Korea.
3. Researcher, Soft Clay Engineering Laboratory, Dong-A Univ., 840 Hadan-dong, Saha-gu, Busan 604-714, Republic of Korea.