FINITE-ELEMENT MODELING OF ROCK-SOCKETED PILES

Rock socketed pile have a number of features which differentiate them from other types of piles. The generally stubby geometry leads to more even distribution of capacity between shaft and base. However, the lo w ratio of pile modulus to rock modulus leads to high compressibility and this, coupled with a tendency for the load transfer response along the shaft to exhibit strain-softening, gives rise to an overall respo nse where the shaft capacity may be fully mobilized, and potentially d egraded, before significant mobilization of base load. The paper prese nts results of finite element analyses of the response of rock-sockete d piles, with particular attention to the shaft response with and with out intimate base contact. The shaft interface uses a model, developed from principles of tribology, that includes dilation (and strain-hard ening) prior to peak shaft friction, followed by strain-softening at l arger displacements. The results of the study are shown to be consiste nt with field measurements, and to capture effects of the absolute pil e diameter on the peak shaft friction. It is also shown that intimate base contact mitigates significantly the degree of strain-softening of the shaft response.