PURPOSE: To eliminate the frictional resistance between a structure and the side ground wall by blowing air in a curtain form from an air jet mechanism provided to the periphery of the structure in the settling work of the structure into the ground.

CONSTITUTION: An air curtain pipe 3 connected through an air supply tube 2 to a compressor is provided in the periphery of a structure 1, e.g., steel shell, caisson etc., to be set into the ground. The structure 1 is penetrated into the ground while blowing air in a curtain form to the periphery of the structure to form air film between the structure and the side ground wall. Since the soil pressure by gradation of the surrounding ground can be reduced when the structure is settled into the ground, the present invention can contribute to the lessening of the frictional resistance.