Performance of dry sandy soil at free field conditions pre-and post-seismic events

Abstract

The bearing capacities of soils and the corresponding settlements are crucial for designing safe and economical structures, but limited research assessed the varieties in the bearing capacities of the soils after an earthquake, despite several studies focusing on sandy soil settlements. This study investigated pre- and post-earthquake bearing capacities and settlements of loose and dense dry sandy soil using laboratory model loading tests and shaking table tests in three stages: first, static loading tests were conducted on strip footings; second, identical models were subjected to sinusoidal waves and real earthquake records on a shaking table under conditions simulating free-field conditions; and finally, samples exposed to seismic motions were retested under static loading to evaluate the effects of peak ground acceleration (PGA), frequency (f), duration (T), Arias Intensity (I_a) on soil response. Results revealed that PGA higher than 0.3 g significantly densified loose sand with post-seismic bearing capacity of the footing increasing up to 0.5 g before stabilizing. Higher f led to pronounced post-seismic soil performance while durations beyond 12 s had minimal impact, implying limits for further densification. Real earthquake records caused moderate volumetric strains and smaller post-seismic bearing capacity increases compared to sinusoidal waves. Initial relative density affected the volumetric strain, with loose sand reaching up to 8 % and dense sand limiting it to 2 %. Amplification was more pronounced in loose soils, increasing with rising PGA and f while slightly reduced by longer durations. These findings provide an understanding of sandy soils under seismic compression and offer a basis for post-seismic bearing capacity predictions.