Discussion of 'Ultimate Shaft Friction and Load-Displacement Response of Axially Loaded Piles in Clay Based on Instrumented Pile Tests' by Kjell Karlsrud

摘要

The author has presented an interesting paper proposing new semi-empirical design procedures for the determination of ultimate shaft friction and load displacement response of axially loaded piles in clays. This proposed design procedure is based on the two main existing models available for estimating the shaft friction for design purposes, namely total stress and effective stress. While the reported shortcomings of each of the two methods are abundant in the literature, these have not been the focus of the paper; rather, the author has recommended that both methods should be utilized and the design values be taken to represent the average of those determined by the two methods. The new design procedures were developed from systematic and rigorous analyses of pile load test data of instrumented and noninstrumented pile tests available in the literature, including those that the author has been involved with over the last 40 years. The new design procedures have incorporated the soil characteristic of plasticity index in both existing models, which has been found to have a significant impact on the mobilized shaft friction, and in the case of the total stress, model significant impact on the adhesion values. Further details of the determination of the findings reported in the paper are contained in the Ph.D. thesis of the author (Karlsrud 2012).