Centrifuge testing on monotonic and cyclic lateral behavior of large-diameter slender piles in sand

Abstract

The existing studies have been primarily focused on the lateral behavior of large-diameter stubby pile or small-diameter slender pile in sand, with little attention paid to large-diameter slender pile. This study presents a unique series of centrifuge tests on monotonic and cyclic lateral behavior of heavily instrumented large-diameter slender piles in medium dense sand. Two typical length to diameter ratios (L/D) are considered with the same length (L = 60 m) but different diameters (D = 4 and 6 m). It is found that the lateral behaviors of large-diameter slender pile, including its monotonic p-y response, cyclic accumulation of lateral displacement and cyclic stiffness evolution, are marginally different from those of small-diameter slender piles, but significantly deviate from the large-diameter stubby piles. This may suggest the longstanding argument of ‘diameter effect’ is relatively minor, while the lateral behavior of monopile in sand is more significantly governed by the relative pile-soil stiffness. The API (2011) non-conservatively predicts both stiffness and capacity of the large-diameter slender piles, leading to development of a new p-y formulation. These centrifuge testing results form a unique database to support development of new design methods for large-diameter slender piles, and to verify advanced numerical analyses involving cyclic models.