Bearing behavior of monopile-friction wheel hybrid foundation under combined horizontal-torsional loads in sand soil

Abstract

The monopile-friction wheel hybrid foundation withstands various loads in the marine environment, such as the vertical load (V) transmitted from the superstructure, horizontal loads (H) caused by wind or wave, torsional loads (T) caused by rotating structures. In this article, 1 g model tests are used to investigate the behavior of the monopile-friction wheel hybrid foundation under independent horizontal load (H) or torsional load (T), and combined loads (H-T) in sand soil, respectively. The failure envelopes of H-T loading plane are obtained from the measured load–displacement data with the simplified calculation equations presented as well. Finally, we also discuss quantitatively the influences of the pre-vertical loads, foundation geometry and loading eccentricity on the bearing capacity of the hybrid foundation via the three-dimensional finite element method. The results indicate that the displacement response of the hybrid foundation under independent loading is significantly different from that subjected to combined loads (H-T). The torsional bearing capacity of the hybrid foundation can be significantly improved by 6.6–33.34% under pre-horizontal load. The horizontal bearing capacity of the hybrid foundation decreases sharply after the pre-torsional load reaches a certain value, which decreases by about 20%. The presence of a friction wheel improves the torsional/bending moment distribution of pile shaft.