Large-Deformation Finite-Element Analysis of Square Foundations in Spatially Variable Sediments

Abstract

Square foundations often penetrate deeply into seabed sediments so that sufficient bearing capacity is obtained, which inevitably induces large-scale deformation in the surrounding sediments. Most of the previous research on square foundations has assumed the sediment had a uniform or linearly increasing strength profile with depth and has ignored the spatial variability of sediments. This work therefore focused on the influence of sediment spatial variability on the behavior of square foundations by applying a random large-deformation finite-element (LDFE) approach. The LDFE results indicated that the sediment heave effect could increase the bearing capacity by up to 15%. This underscores the advantages of LDFE analysis for bearing capacity predictions. More importantly, the mean bearing capacity from random analyses is smaller than the deterministic solution in uniform sediments. Consequently, deterministic analysis yields an overestimated bearing capacity. Finally, a framework was established for estimating the probability of failure at various depths considering a random sediment strength based on a factor of safety (FOS). This indicated that the partial FOS recommended by the Det Norske Veritas code is equivalent to a probability of failure of 0.1%. Our findings may facilitate the evaluation of the probability of failure for deterministic foundation design based on the FOS.