Abstract: During the ascent process of underwater vehicles in ice covered water, it is necessary to apply a vertical load on the ice sheet to break through the ice sheet. Therefore, the vertical ice-breaking load becomes an important parameter for the vehicle design. To investigate the bearing capacity of the ice sheet under the vertical load, field experiments were conducted on freshwater ice covers. This study focuses on naturally formed ice covers and an apparatus was designed to apply the concentrated vertical load on the bottom of the ice cover and move up through the ice covers. The experiments were performed on various thicknesses of ice covers and the surface temperature of each ice layer was measured. Additionally, the displacement and force of the load head, as well as the ice failure process were recorded. The experimental results indicate that the ice cover can fail in shear and bending modes. The fitting curve of the result shows that the maximum load and the thickness follow a positive power correlation. To analyze the influence of ice thickness on the transition of ice cover failure modes, the ice cover was simplified as an idealized elastic model. The bending stress of the ice layer is inversely proportional to the square of the ice layer thickness, while the shear stress is inversely proportional to the ice layer thickness. Temperature can affect the strength characteristics of ice layers, thereby influencing the ice failure mode. As the temperature increases, the failure mode of the ice layer gradually transitions from shear failure to bending failure.