Effect of Anisotropy Spatial Variability of Multi-Layered Soil on the Bearing Capacity of Offshore Single Pile Composite Foundation

The bearing capacity of offshore single pile composite foundations is significantly influenced by spatially variable soil properties and the presence of different soil layers during pile installation. Previous research has primarily focused on the effects of isotropic or transversely anisotropic spatial variability of soil on the bearing capacity and failure mechanisms of piles embedded in a single homogeneous soil layer. However, practical offshore sites often consist of multiple soil layers, where soil properties can exhibit pronounced rotated anisotropy due to complex geological processes. The impact of such rotated anisotropic spatial variability on the bearing capacity of offshore single pile composite foundations embedded in multiple soil layers remains poorly understood.This study systematically investigates the effects of rotated anisotropic three-dimensional spatial variability of soil properties on the bearing capacity of offshore single pile composite foundations embedded in two distinct soil layers. A three-dimensional random finite element method is employed to simulate the pile-soil interaction under vertical static loads. The study examines the influence of the scale of fluctuation ('), the rotated anisotropy angle, and the coefficient of variation (COV) of soil parameters including elastic modulus (E), cohesion (c), and internal friction angle (AE) on the failure mechanism and the characteristic bearing capacity of the pile. The result shows that the rotated anisotropy of the upper-layer soil generally exerts a more significant effect on the pile’s bearing capacity compared to the lower-layer soil, especially when the horizontal scale of fluctuation is large. These findings highlight the critical importance of considering rotated anisotropy spatial variability in the design and analysis of offshore single pile composite foundations.

Keywords: Spatial variability, Rotated anisotropy, Offshore pile composite foundation, Vertical bearing capacity, Monto Carlo Simulation.