Generation of negative skin friction and drag load in near-offshore pile foundations: A numerical study addressing pile installation effects

Offshore and near-offshore infrastructures are primarily supported by pile foundations for transferring the super-structure load to the bearing stratum while bypassing the overlying soft consolidating medium. Apart from the characteristics of the surrounding consolidating soil medium, pile installation process can also significantly influence the development of negative skin friction on the installed piles for such applications. The present study elucidates the evolution of negative skin friction on both in-place and jacked pile with the aid of an updated Lagrangian-based 2D-axisymmetric finite-element simulation framework. A particular emphasis is given on the determination of optimum values of parameters like pile-tip cone angle, contact stiffness and mesh size etc., which becomes imperative for the simulation of pile penetration process exhibiting a large deformation phenomenon. Post installation of the pile, the surrounding soil is subjected to a surficial surcharge to induce consolidation settlement of soil strata. In contrary to the in-place pile, the squeezing effect induced by the penetration process of a jacked pile leads to the dissipation of higher excess pore-water pressure and subsequent marked increase in the effective radial stress. Consequently, it further leads to a higher negative skin friction and greater drag load on the jacked pile.