Base resistance of open ended piles evaluated by various design methods
The design bearing capacity of an open ended pile depends largely on the accuracy of the design method. Although the knowledge of shaft resistance has been understood quite well, the base resistance has not yet been completely understood due to the effects of soil plugging. The mechanisms of soil plugging is yet to be fully understood particularly for large diameter and long length piles installed in large construction projects. This paper compares the base resistance of two open ended field piles constructed in the Tokyo Bay project evaluated by various design methods including cone penetration test (CPT)and standard penetration test (SPT) based methods. In total, five design methods including the conventional American Petroleum Institute (API) approach were included. In Japan, SPT based design methods are used in practice. The CPTbased design methods, which are not popular in Japan were also included to evaluate their effectiveness. The CPT design methods discussed in this paper classify open ended piles into plugged or unplugged modes. The results reveal that the Fugro (i.e. CPT based) and the API design methods overestimate the base resistance. In contrast, the ICP (i.e. CPT based) and Port and Airport Research Institute (PARI) (i.e. SPT based) design methods underestimate the base resistance. Based on the results, we can recommend the University of Western Australia (UWA) design method (i.e. CPT based) as it produces the nearest results to the actual base resistance measured from the field load tests.