Centrifugal tests on embankment subjected to combined effects of rainfall and earthquake

This study investigates the fundamental behaviour of road embankments subjected to sequential rainfall infiltration and seismic loading using a newly developed centrifuge rainfall simulator. Two model embankments with different degrees of compaction (D_c = 82% and 90%) were tested under 30G centrifugal gravitational field, followed by seismic excitation using the Kobe earthquake record. The rainfall tests reproduced pore water pressure increases at the embankment base, with lower-density embankments (CASE1, D_c = 82%) exhibiting faster infiltration and earlier rise in pore water pressure, while higher-density embankments (CASE2, D_c = 90%) showed delayed but larger increases due to lower permeability. Before seismic excitation, both cases reached comparable groundwater levels of approximately half the embankment height. Under seismic loading, CASE1 developed significant excess pore water pressure near the toe, leading to liquefaction, large deformation, and flow sliding. Maximum shear strain reached 50%, propagating from the toe to the crest. In contrast, CASE2 generated negligible excess pore water pressure, resulting instead in amplified accelerations at the embankment shoulder and limited deformation with maximum shear strain ∼10%. These results demonstrate that embankment density governs infiltration behaviour, pore water pressure generation, and subsequent seismic deformation mechanisms.