Abstract
The development of limit-state design codes for large-diameter bored piles requires a careful calibration of existing design methods. Due to various sources of uncertainty in understanding the geology and construction details, estimation of design loads, and design analysis models and their parameters, the estimated pile capacity values from several design methods for large-diameter bored piles vary widely and the corresponding reliability levels are not clearly known. This paper aims at evaluating the performance of six design methods for bored piles in soils and four design methods for bored piles socketed in rocks based on a database of 62 full-scale load tests on large-diameter bored piles in Hong Kong. These methods include a descriptive method, the β-method, and several empirical correlations with blow count from the standard penetration test or unconfined compressive strength of rock. The capability of these design methods to estimate individual resistance components and the total capacity is calibrated separately. Construction effects, particularly the use of permanent liners, pile-shaft grouting, and the time delay between the end of pile excavation and pile concreting, are explicitly considered. The performance of each design method is indicated by the first and second moments of the model bias factor, which can be used as a basis for developing partial factors for limit state design.
