Dynamic response of stand-alone and adjacent footing on saturated sand

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This paper presents results from geotechnical centrifuge tests performed at the Japanese Institute of Occupational Safety and Health (JNIOSH) in Tokyo, Japan. A range of shallow footing configurations with different bearing pressures founded on saturated sand in a laminar box on a shake table was studied using harmonic excitations. The free-field condition was also studied as a reference. The study aimed to address the influence of stand-alone and closely adjacent shallow foundations on the dynamic response of the soil-foundation-structure system. A partially drained response of the soil and a minor dilative response for large values of shear strain were observed for the free-field case. In the case with footings, the settlement was found to be largely due to the footing penetrating the supporting sand. A dilative response of the soil beneath the footings was observed for the stand-alone configurations at the beginning of the base motions, this was not observed in the case of adjacent footings. Adjacent footings also tilt inwards consistently while stand-alone footings did not present a clear tilt pattern. In terms of the acceleration recorded in the near-surface soil beneath the footings, a reduction was observed after a few cycles in the free-field case. This reduction was considerably smaller in the case with footings with no significant differences between the response of the stand-alone and that of the closely adjacent footings.