Abstract: In order to study the structural mechanical properties and weak points of the bundled integrate structure, a full-scale test on the quarter structure had been conducted. The unloading condition of the side was studied by keeping the top load corresponding to 4 times of the design buried depth. The results showed that: (1)With the increase of the load difference between the upper and the side, the joint at the side was detached, the overall stiffness of the structure decreased by 87%, and the joint opening, structural deformation and prestressed tendon strain increased significantly. (2) After the side part was completely unloaded, the structure had obvious deformation, but it still had a certain bearing capacity. (3) In the whole process of the experiment, the structural stiffness first decreased, then increased and finally decreased substantially. The final stiffness was only 36% of the initial stiffness.