토질의 불확실성을 고려한 지반설계변수의 결정

Abstract

Recently, limit state design (LSD) in geotechnical engineering has been developed through LRFD in North America and Eurocode 7 in Europe. LRFD is an approach that estimates resistance by design model and that multiplies resistance factor by calculated resistance to reflect the uncertainty of materials and design models. Whereas, Eurocode 7 employs the partial resistance factor applied directly to each variable in resistance equation that individual soil properties such as cohesion and angle of internal friction are applied. In this paper, Current estimation methods of characteristic value were discussed with the marine clay of Korea within the framework of characteristic value which has globally argued during the processing of development of Eurocode 7 for geotechnical design even to the present. Estimation of characteristic value, an issue of this dispute, affects not only determination of design value applied directly to design of geotechnical structures, but also economic feasibility and stability following results of design. In this paper, the characteristic values for main marine clay were calculated and compared with using some methods proposed. As a result, it was appeared that most of the computed were close to mean value and less conservative in the order of Student/Ovesen, Schneider and EN 1990. In case of EN 1990 approach, however, it was inappropriate to assess geotechnical design value being calculated less than zero with statistical variability. Also, it was found that current methods have trend of estimating more conservative characteristic values when larger in ground variability.