Responses of reinforced concrete pile group in two-layered liquefied soils: shake-table investigations

During earthquakes, the response of pile foundations in liquefiable sand reinforced by densification techniques is still a very complex dynamic soil-structure interaction problem. Two shake-table experiments were conducted to investigate the behavior of a reinforced concrete (RC) low-cap pile group embedded in liquefiable soils. Discussion is focused on the behavior of soil-pile-superstructure systems prior to and during liquefaction of the medium-dense and dense sand stratums, which are involved in restoring force characteristics at the superstructure and pile group effect. The test results demonstrated a stiffness reduction and dependent nonlinear behavior appearing in the liquefied medium-dense sand; however, an overall stiffening response was observed in liquefied dense sand. The pile group effect seemed insignificant in liquefied medium-dense sand, but was very significant in the liquefied dense sand.