Large-Scale Experimental and Numerical Studies on the Dynamic Interaction of Closely Spaced Machine Foundations on Geogrid-Reinforced Soil Beds

The current study encompasses experimental and numerical investigations on the response of closely placed machine foundations resting on unreinforced and geogrid-reinforced soil beds. Large-scale field block vibration tests are performed on isolated and closely spaced block footings resting on prepared foundation beds at IIT Kanpur, India. The dynamic interaction between machine foundations is explored by considering various combinations of footings, in which one footing (active footing) is dynamically loaded, while the other (passive footing) is loaded statically. The tests involve three eccentric force settings for four distinct footing combinations at different clear spacings and reinforcement conditions. Steady-state vibrational responses are recorded for both active and passive footings. The experimental outcomes indicate that incorporating the geogrid causes a reduction in the resonant displacement amplitude and an improvement in the resonant frequency of both active and passive footings. For active footings, the resonant displacement amplitude decreases by 27%, while the resonant frequency increases by 21% in the presence of the geogrid. In contrast, for passive footings, the presence of the geogrid leads to a decrease in the resonant displacement amplitude by 21% and an increase in the resonant frequency by 1.2 times. The current investigation also presents the attenuation response of unreinforced and reinforced soil beds. The geogrid mitigates vibration propagation efficiently by reducing ground-borne vibrations. Including the geogrid in the foundation bed reduces ground vibrations by 39% at a distance of 0.6 m from the vibration source. A 3D finite-element (FE) model is developed for the numerical analysis. The established FE model captures the dynamic interference effect and the attenuation response under different bed conditions. A comparative study between the experimental and the numerical results demonstrates a promising level of agreement, affirming the efficacy of the developed numerical model.