Practical operations in South China Sea find that punch-through could happen in soft clay. In order to get more bearing capacity of foundations, new jack-up units are equipped with large-scale spudans. Large spudcans can improve adaptability, but also increase the damage of punch-through accidents. We designed a force loading penetrating and removing experiment apparatus of jack-up unit, which can apply graduated loading in the progress of penetrating. The generation of artificial rigid layer is related to loading velocity, the higher the loading velocity is, the greater the possibility of artificial rigid layer will be.