Experimental investigation of the vertical pullout cyclic response of bucket foundations in sand

•Cyclic response of bucket foundations in saturated sand under cyclic vertical pullout load was examined by 1g model tests.•Accumulated displacement increased with the increase in number of load cycles and load magnitude.•Unloading stiffness decreased with the increase in number of load cycles and load magnitude.•Empirical equations have been proposed. A series of 1g model tests was conducted to investigate the accumulated vertical pullout displacement and unloading stiffness of bucket foundations embedded in dry and saturated sands. The foundations were subjected to vertical pullout cyclic loading with different load amplitudes. Cyclic load was applied up to 104 cycles. Test results showed that the accumulated vertical pullout displacement increased with the increase in the number of load cycles and cyclic load amplitudes. The unloading stiffness of the bucket foundations decreased with the increase in load amplitude and number of cycles. Empirical equations were proposed based on the test results to evaluate the accumulated vertical pullout displacement and unloading stiffness of the bucket foundations in saturated sand. These equations can be used for the preliminary design of single or tripod bucket foundations.