An Approach for Assessing Geotechnical Reduction Factors for Pile Design

摘要

Design of piles in Australia is based on the Australian Piling Code, AS 2159 - 1995. For geotechnical design of piles for the ultimate limit state, it is necessary that the designer selects an appropriate geotechnical reduction factor, Φ_g, which is applied to the estimated ultimate geotechnical capacity. The Code tabulates various ranges of Φ_g, depending on the method of analysis employed, the level of testing, and other conditions pertaining to the project. Selection of Φ_g requires a good measure of judgement from the designer. This paper describes an approach for making a more rational selection of Φ_g. It employs, in a simplistic manner, elementary reliability concepts and calibrates the level of uncertainty with commonly-employed overall factors of safety. It then derives geotechnical reduction factors from these overall safety factors. A process is then described for quantifying the level of uncertainty and risk for a particular project into an overall risk rating, which is then used to select an appropriate value of Φ_g. The application of the method is illustrated with respect to a high-rise development in South East Asia.