Abstract: In designing pile-tube composite foundations, it is crucial to consider the impact of various load combinations to ensure the structure's safety and stability. Utilizing ABAQUS, a finite element model was developed to simulate the stress conditions of a 3 MW wind turbine pile-tube foundation in homogeneous soft clay soil. Through a load-displacement loading method, a normalized two-dimensional load space failure envelope was obtained to analyze the failure modes and soil deformation patterns under compound loading conditions. The results indicate that a certain vertical load is beneficial for the foundation's bearing capacity, while simultaneous horizontal and moment loads exacerbate failure. The failure modes of the foundation under compound loading vary with different proportions of load components. The V-H and V-M loading modes exhibit similar failure patterns, progressing through stages of vertical scoop failure, spherical rotational failure, horizontal wedge sliding, and overturning failure. In contrast, the H-M loading mode displays more complex failure patterns, including forward overturning, scoop-wedge failure, backward translation, and backward overturning.