Model tests on jacking installation and lateral loading performance of jacket foundation in sand

Abstract

The long-term dynamic behavior of pile under cyclic loads is important for the stability and safety characteristics of jacket supported offshore wind turbine. In this study, large-scale indoor model tests were carried out on the jacking installation and lateral loading of jacket foundation in sand. For the process of pile installation, it shows that the linear growth of pile tip resistance during installation can be divided into two stages, and its critical depth (the depth at which the growth rate of pile tip resistance begins to decrease significantly) is 11D (diameter). The jacking resistance of latter pile is significantly greater than that of former pile. Under static load, the maximum bending moment point of front row pile is higher than that of back row pile. The depth of bending moment reverse point is also 11D for front and back row piles. Under cyclic loads, the displacement at tower top undergoes two stages: rapid growth stage and slow growth stage. The friction resistance of back row pile increases first and then decreases along depth, showing an oblique “V” shape. The natural frequency varies with different load frequencies and cyclic load ratios. The evolution trend of system damping ratio and natural frequency is roughly opposite.