A series of 1 g experimental tests was conducted to investigate the effect of drainage condition on the pullout characteristics of bucket foundations in sand. Model buckets with a constant diameter of 150 mm and length-todiameter ratios of 1.5, 1.0 and 0.5 were employed with pullout rates ranging from 0.05 mm/s to 20 mm/s. The phenomena of heaving, gapping below the lid, and suction pressure have been investigated and discussed. The peak pullout load, peak suction pressure and heave increased with the increase in the pullout rate and L/D. The drainage factor was proposed to classify the drainage conditions during bucket pullout. The drainage factor is a function of the pullout rate and the inflow velocity. The inflow velocity converged to a nearly constant value defined as the critical inflow velocity. The pullout rates beyond the critical inflow velocity induced undrained conditions. The drainage conditions were classified as drained, partially drained, and undrained based on the proposed drainage factor. The drainage factor criterion reasonably classified the drainage conditions induced at peak pullout load.
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