1. Graduate Student, School of Civil, Environmental and Architectural Engineering, Korea Univ., 1, 5-ga, Anam-dong, Sungbuk-gu, Seoul 136-713, KP.
2. Professor, School of Civil, Environmental and Architectural Engineering, Korea Univ., 255-53, Anam-dong, Sungbuk-gu, Seoul, 136-713, KP (Corresponding author), e-mail: jongsub@korea.ac.kr
3. Senior Researcher, Geotechnical Engineering Research Division, Korea Institute of Construction Technology, Goyang 411-712, KP.
4. Research Fellow, Geotechnical Engineering Research Division, Korea Institute of Construction Technology, Goyang 411-712, KP.