Long-Term Foundation Response to Repetitive Loading

Abstract

Repetitive loading can induce volumetric and shear strain accumulation in soils and affect the long-term performance of engineered and natural geosystems. A hybrid numerical scheme based on the FEM is implemented to analyze problems where a very large number of cycles is involved. The numerical approach combines a classical mechanical constitutive model to simulate the static load and the first load cycle and empirical accumulation functions to track the accumulation of deformations during repetitive loading. The hybrid model captures fundamental characteristics of soil behavior under repetitive loading, such as threshold strains, terminal density, and ratcheting response; it also predicts volumetric and shear strains as a function of the static stress obliquity, the number of load cycles, and the plastic strain during the first load cycle. The proposed numerical scheme is used to analyze shallow foundations subjected to repetitive loads. Results show the evolution of vertical settlement, horizontal displacement, footing rotation, and stress redistribution within the soil mass as the number of load cycles increases. Displacements and rotation are more pronounced as the static factor of safety decreases and the cyclic load amplitude increases.