Interface friction evolution of FRP tube confined concrete piles during the driving installation process

The surface topography of fibre-reinforced polymer (FRP) tube confined concrete piles may be significantly altered during the driving installation process. This change could affect the interface pile design parameters and therefore an accurate quantification of this change is required to precisely determine the pile shaft resistance. This article presents the results of an experimental study carried out to investigate the changes in surface topography and interface shear coefficient of two different FRP counterface surfaces that sheared against different types of sand under increased normal stress levels. The test results indicate that quantifiable surface topography changes could be induced by subjecting FRP surfaces to interface shearing under increased normal stress levels. Furthermore, the interface shear resistance coefficient decreases as the normal stress increases. The study also shows that the deterioration of the interface shear resistance coefficient as the normal stress increases can be mainly attributed to the interface dilatancy behaviour. However, the effect of surface topography change on the deterioration rate is a function of the hardness of the counterface material.