PRACTICAL DETERMINATION METHOD FOR SOIL PARAMETERS ADOPTED IN THE NEW PERFORMANCE BASED DESIGN CODE FOR PORT FACILITIES IN JAPAN(<Special Issue>Recent Attempts to Establish Performance-based Design of Geotechnical Structures)

概要

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The Japanese design code for port facilities was revised in April 2007, and a performance-based reliability design method was introduced. This report introduces a new practical method, which has been adopted in the annex of the design code, to evaluate soil parameters. The new method uses a correction factor corresponding to the coefficient of data variation. In this method, the characteristic value automatically reflects the variation of the derived values in association with the testing method and the reliability of the data interpretation. Compared to the lower limit of 95% confidence interval, which is widely adopted in general design codes such as Eurocode 7 and JGS4001, the characteristic value determined by this method is conservative when the number of data entries is larger than 10. This tendency is caused by the concept, in which characteristic values always reflect the data variation, even though the number of data entries are significantly large. Generally, data variation in the depth profile can be reduced when the depth distribution is appropriately modeled. Also, data variation can be reduced by adopting a more reliable soil test. Accordingly, any efforts to reduce the variation are awarded in this new design code.