Experimental and Numerical Investigation of the Performance of Piles and Suction Caissons Subjected to Inclined Cyclic Loading in Cohesive Soils

Abstract

Cyclic loading on caisson and pile anchors can be a significant design issue, particularly with respect to cumulative vertical displacements that can lead to reduction in embedment depth and load capacity of the anchor. Most existing design methodologies are based on monotonic load capacity, often accounting for potential soil strength degradation due to cyclic loading. Because the cyclic strength criterion is often based on cumulative strains, these approaches arguably implicitly consider cumulative deformations. However, cumulative plastic deformations under storm conditions should be investigated. Piles and caissons serving as anchors for floating offshore structures experience inclined cyclic loading. This paper presents (1) monotonic and cyclic loading tests in the vertical and lateral directions, and (2) a finite-element (FE) investigation of different aspect ratios (L/D=4, 5, and 6) of caissons subjected to different load angles (ψ=0° to 45° from the horizontal). Additionally, it presents a precise method to calibrate the constitutive model (nonlinear kinematic hardening model), where the calibrated model was match to monotonic and cyclic lateral and vertical loading tests. Nonuniform load amplitudes were used in the FE investigation. The primary finding from the investigation was that the influence of the cumulative displacements increases when increasing the load amplitudes, especially for the load inclinations of 0°–20° for the lateral displacements and 20°–45° for the vertical displacements.