Dynamic Stiffness, Damping, and Wave Propagation of Foundations on Improved Soil

Dynamic loads generated by winds, waves, and machine loads can cause excessive vibrations of foundations when resting on loose sands or soft clays. Ground improvement can reduce such vibrations. It can also provide a lower carbon footprint solution compared to piling. Improvement effects are not fully developed in the literature. This paper studies the effect of soil improvement on the performance of foundations subjected to dynamic vertical and lateral loads. An analytical solution is developed based on the equivalent damped oscillator model. The stiffness and damping were determined from finite element analyses at different improvement depths and stiffness ratios. Results show that soil improvement can increase stiffness and damping significantly which would reduce the amplitude of vibration of the foundation. Propagation of waves away from the foundation was also studied, and it was shown that vertical vibrations decay faster than lateral vibrations. Charts are provided that can assist in practical design of foundations on improved soils that are subjected to dynamic loads.