Discussion of “Distribution of residual load and true shaft resistance for a driven instrumented test pile”1Appears in the Canadian Geotechnical Journal,48(4): 583–598 [doi: 10.1139/t10-084

Abstract

The authors have presented a well-documented case study of the load test interpretation of prestressed high-strength concrete (PHC) piles, which are very popular in the Far East and are often favoured over steel piles on the basis of cost. Despite their popularity, well-analyzed load test case histories are rare and hence the authors’ paper is a valuable contribution to the technical knowledge base. Although the authors’ have considered the geotechnical aspects in detail, the discussers believe that this case study also would benefit from a fuller analysis of the structural conditions of the piles. This is because the authors have identified that the key design aspects for this site are actually the maximum load in the pile and the pile structural strength, but not the pile capacity. Based on the load test results, the authors concluded that the long-term maximum load in the pile will approach the pile structural strength and hence grouting the central void should be considered. The discussers have carried out an assessment of the pile strength using a different approach and compared the results with the current design guidelines. It was found that even with the central void grouted, the PHC piles are still not sufficiently robust and a different pile size or type may need to be considered. The discussers’ assessment and, where appropriate, comparisons with the authors’ results are described as follows.