Numerical study of local scour effects on the lateral pile-soil interaction

Abstract

Local scour usually occurs around offshore pile foundations, which may bring the reduction of both the effective stresses in the surrounding soil and the effective pile embedment. Until now, the effects of local scour on the lateral pile-soil interaction have not been well understood. In this study, a 3-D finite element model for the lateral pile-soil interaction is proposed and verified with experimental results. An improved analysis approach is further presented for evaluating the local scour effects on the lateral pile-soil interaction by extracting p-y curves from the numerical results. The results indicate that scour could induce a significant transition of pile behavior for a monopile typically employed for offshore wind turbines. If the pile exhibits rigid structural behaviors after scour, the pile’s tip and shaft resistance may become a significant component of the whole soil resistance, which would render the traditional p-y approach inapplicable. For a given depth below the scour base, the p-y curves get significantly stiffer with increasing scour depth, especially at relatively shallow depths. The scour effects on the variation of p-y curves from the present numerical results are generally consistent with the existing centrifuge results. As the slope angle of scour holes decreases, the effect of the remaining sloping overburden soil above the level of the scour base reduces and the stiffening of the p-y curves at a given depth below the scour base is correspondingly alleviated.