Abstract:A scaled 4-pile jacket wind turbine model was used to study the impact of scour holes on the jacket stiffness. The scouring process was simulated by controlling the occurrence sequence of scour holes and different scour depths of jacket foundation and this paper investigated the influence of local scour holes on the distribution of internal forces and stiffness of jacket foundation under static load. The results show that: when the load is small, the influence of local hole within 1.5D (Dis the pile diameter) on the static stiffness of jacket is small; But the impact of scour hole on the static stiffness increases gradually with the increase of load, because with the increase of load, the axial force of the back-row pile gradually shifts from compression to tension, which leads to the stiffness decreaseof the pile. For the resonance frequency of jacket, the study shows that when the depth of the scour hole is greater than 1D, jacket resonance frequency started to decrease; At this time, any pile with a deeper hole will cause the resonance frequency to drop; When the local scour depth is 1.5D, the first-order resonance frequency of the wind turbine decreases about 3.2%, while the resonance frequency of the wind turbine decreases by about 6.3% when the scour depth is 2D. When the shape of scour hole is conical and the depth of local scour is kept unchanged, the change of the scour hole slope will cause a small change in the resonance frequency of jacket wind turbine.