Centrifuge shaking table tests on the seismic response of an underground structure in saturated coral sand

This study investigates the seismic behaviour of an underground structure in saturated coral sand using centrifuge shaking table tests. The research focuses on the overall displacement pattern, uplift mechanism, acceleration response, and dynamic soil pressure acting on the structure. The results reveal that the displacement process comprises three distinct phases: initial horizontal swaying (Phase I), coupled horizontal swaying and uplift (Phase II), and a return to horizontal swaying (Phase III). This phase transition occurred due to changes in vertical force equilibrium caused by the development of excess pore pressure (EPP) in the soil layers surrounding the structure during shaking. Apart from the EPP, the uplift was also closely related to its duration in Phase II. The normalised cumulative excess pore pressure index (Icp) was introduced to describe the relationship between the peak uplift displacement of the structure and both the magnitude and duration of EPP in Phase II. Additionally, the acceleration response spectra of the structure were significantly affected by the liquefaction depth (Zliq) of soil beneath the structure. Dynamic soil pressure responses on the structure's sidewalls and bottom exhibited significant discrepancies due to differences in EPP in the surrounding soil.