Large-scale laboratory tests of a new type of bucket foundation in sand subjected to vertical loading

Abstract

As a new breakwater foundation form, a bucket foundation with two skirted side semicircles and a skirted middle rectangle was applied to the breakwater project at Xuyu Port, China. A series of laboratory tests were performed on the bucket foundation to investigate the vertical bearing capacity and the bucket-sand interaction mechanisms during the load bearing process. The main failure mode of the bucket foundation under vertical loading was general shear failure. The vertical loads increased with penetration displacement, ultimately reaching 330~404 kN with a displacement criterion of 0.06De (equivalent diameter of the foundation) at different incremental load steps. The inner soil pressures were clearly greater than the outer soil pressures induced by the skirt constraint effect. Regarding the bearing capacity, the outer skirt friction decreasing from approximately 0.05 to 0 with increasing penetration displacement, contributed only slightly, while the foundation base provided the majority. The cover plate resistance increased rapidly after the penetration displacement exceeded 25 mm, and its sharing ratio ultimately reached approximately 0.82. The tip resistance was estimated via the assistance of the cone resistance, and its sharing ratio decreased with penetration displacement. The inner friction and corresponding friction coefficient first increased and then decreased with penetration displacement, reaching a final sharing ratio of approximately 0.14.