Life cycle changes in p-y stiffness for a conductor pile installed in carbonate silt

Abstract

Lateral soil stiffness has a strong influence on the overall strength and fatigue life of well conductors and piles. This paper reviews data from centrifuge testing of a short model pile embedded in carbonate silt, which was subjected to packets of cyclic lateral displacement. Key conclusions are that (i) cyclic lateral stiffness is significantly affected by prior loading history due to the generation and dissipation of pore pressure, (ii) the generation process leads to the well-recognized softening of p-y curves, (iii) the dissipation process leads to a less-recognised stiffening of the response, and (iv) carbonate silts show a different shape of cyclic lateral response compared to non-carbonate clays, meaning that existing ‘fully degraded’ steady state p-y models are not appropriate. Future ideas to capture these improvements in lateral response modelling are set out, with the aim of allowing more accurate and reliable design of conductors and piles.