Scour-induced unloading effects on lateral response of large-diameter monopiles in dense sand

Scour significantly influences the lateral response of pile foundations; however, there is a lack of comprehensive understanding regarding the scour effects on the lateral pile-soil interactions. This study employs finite element analysis to investigate the scour-induced unloading effect on the lateral response of large-diameter monopiles embedded in dense sand. This unloading effect results in stress redistribution within the soil, consequently altering the strength and stiffness, and influencing the resistance to failure and deformation of pile foundations. To effectively characterize this scour-induced stress redistribution, a cone penetrometer-based approach is utilized, which correlates Young's modulus of the sand with the cone penetration resistance. A modified Mohr-Coulomb model that considers effects of updated geostatic stress on the stress-strain behavior of dense sand is adopted in the FE analysis. Scour can lead to a reduction in the strength and stiffness of shallow layers of the remaining soil. The stress concentration induced around the pile base due to post-scour geostress reequilibrium can affect the lateral response of the pile. Furthermore, the effect of scour hole slope angle on the lateral response of pile foundations is quantified through the approach of effective soil depth. Finally, the formulas for evaluating scour effect on p-y curves are refined to extend its applications to arbitray slope angles of the scour hole by incorporating the present numerical results.