Effects of embedment depth on the pullout capacity of bucket foundations in sand

Abstract

A series of 1 g experimental tests was conducted to investigate the effects of embedment depth on the pullout capacity of bucket foundations in sand. Polycarbonate model buckets with a constant diameter of 150 mm and length-to-diameter (L/D) ratios of 0.5, 1.0 and 1.5 were employed varying loading rates from 0.002 N/s to 4.1 N/s. The slow loading rate of 0.002 N/s induced drained conditions characterised with substantially small suction force and high skirt resistance. The fast loading rate of 4.1 N/s induced nearly undrained conditions characterised by large suction force and almost full uplift of the soil plug. The pullout capacity increased almost linearly with the L/D ratio. A 50% increase in embedment depth resulted in an average increase in pullout capacity of 40%. The pullout capacity and suction force inside the bucket rapidly increased with the loading rate in the partially drained condition, and converged to nearly constant values in the undrained condition. In the nearly undrained condition, the suction force at the tip was approximately half of that under the lid. The simplified approach reasonably predicted the capacities of buckets with various L/D ratios.