Numerical modelling of pile installation and set-up effects on pile shaft capacity

Soil set-up effects significantly contribute to the increase in shaft bearing capacity of prefabricated displacement piles installed in saturated clay. This paper quantitatively distinguishes the effects of two contributing factors, (1) excess pore water pressure dissipation and (2) aging. A large-deformation coupled analysis using a finite-element scheme is used to carry out the analyses. The model only captures excess pore water pressure effect and the differences in skin friction between field measurements and numerical predictions are considered as aging. The results show that the coefficient of lateral earth pressure adjacent to the pile skin increases over time to 2.5 times of the initial coefficient (at rest). Numerical simulation of load-displacement response of static load tests at different times show that the contribution of the first factor which increases the shaft resistance is initially more significant. As time passes, the magnitude of the second factor (aging) becomes more significant..