To address the issue of calculating negative skin friction for wind turbine pile foundations in collapsible loess areas

this paper conducts large-scale indoor model tests and compiles field test data from similar projects. After investigating the relationships between the collapsible settlement depth of loess after complete immersion

the depth of the neutral point

the depth of maximum negative skin friction

and the pile length-to-diameter ratio

expressions for the depth of the neutral point and the depth of maximum negative skin friction in terms of collapsible settlement depth and pile length-to-diameter ratio are derived through linear fitting. On this basis

a method for calculating negative skin friction of wind turbine pile foundations in collapsible loess areas is established. The results calculated by the proposed method and the method specified in the pile foundation code are compared with the measured results respectively. The findings indicate that the downward pull load calculated by the method in this paper is closer to the actual situation than that obtained using the pile foundation code. This achievement can provide a reference for the design of similar pile foundation projects.