Efficacy of a Hybrid Foundation to Mitigate Liquefaction-induced Effects Under Strong Sequential Ground Motions

Abstract

A hybrid foundation is developed to mitigate the liquefaction-induced effects on a shallow foundation. The proposed hybrid foundation is a combination of the gravel drainage system and friction piles having spiral blades devised under the footing as a hybrid mitigation technique against the liquefaction-induced effects on a shallow foundation. Any structure situated on liquefiable ground may experience several moderate to strong earthquakes during its lifespan. Therefore, the effectiveness of adopted mitigation techniques under sequential ground motions is necessary to examine the long-term efficacy of their performance to mitigate the liquefaction-induced effects. A series of dynamic centrifuge experiments are carried out to investigate the effectiveness of a hybrid foundation in the liquefiable ground under strong sequential ground motions. Ground motion recorded at Hachinohe Port during the 1968 Tokachi-Oki earthquake (NS component) and design earthquake motion for highway bridges in Japan (2-I-I-3, NS component) recorded at the ground surface near New Bansuikyo Bridge, Tochigi, during the 2011 Tohoku Earthquake are used as the sequential ground motion. The second sequential ground motion is found to be diminishing the mitigation efficacy of the proposed hybrid foundation in comparison with the first sequential ground motion. The implications of strong sequential ground motions are also discussed.