Numerical analysis of bearing capacity of winged helical anchor in clayed soil

Adding wings is an effective method to improve the lateral bearing capacity of helical anchor to meet the requirement of combined loading. However, the study on winged helical anchors is scarce. Therefore, this paper used numerical method to investigate the lateral and vertical bearing capacities and failure modes of winged helical anchors in mixed soil (cohesive material with internal friction). The addition of wings at the top of the helical anchor enhances the ultimate lateral capacity (ULC) significantly when ULC is controlled by displacement of 10% helix diameter, which increases with the height and width of wings. But the effect of wing height is limited, once the height exceeds the maximum soil mobilization depth induced by wing or shaft under lateral loading, the ULC essentially stops increasing. As the relative wing width B/D increases, although the increase rate in ULC gradually slows down, obvious increase is still observed at B/D = 1.5. The ULC reaches 4 times that of a wingless helical anchor for the case of helical anchor with relative wing height h/D of 2 and width B/D of 1.5. The calculation method of ULC is proposed combining the analysis of displacement field at failure, and the safety factors for design are also suggested. The vertical tensile and compressive bearing capacities of wingless anchor are similar when installations are not considered. Each helix with a spacing greater than 1.53D exhibits an independent failure mode when using 0.1D as the failure criterion. And Terzaghi's formula for the bearing capacity of circular foundations can effectively estimate the ultimate vertical bearing capacity of helical plates. The ultimate end resistance q_cu of the wings decreases logarithmically with increasing aspect ratio of wing base B/t. The Meyerhof's bearing capacity factors for deep strip foundations are recommended to calculate q_cu of wings with B/t no less than 15. This study can provide reference for design engineers to estimate the lateral and vertical bearing capacities of winged helical anchors.