PURPOSE: To shorten the period of construction as well as reduce the cost of construction by a method in which an oval-shaped one unit is formed by drilling a pit by a multiple-shaft auger, excavated soil is mixed with a solidifying agent with stirring, and stress materials are penetrated to form a sheathing wall.

CONSTITUTION: The ground is excavated and stirred by means of excavating blades 2 and stirring blade 3 by turning the excavating shafts 1 of a multiple shaft auger. The ground is cut by the cutting blade 5a of a cutter 5 loosely fitted into the excavating shaft 1 to form an oval-shaped pit. The device is pulled up while injecting a solidifying agent, e.g., soil cement, etc., from the jet nozzle 4 at the tip of the excavating shaft 1 of the auger and also while stirring soil by the blade 3, and stress materials e.g., H-shape steels, etc., are erected to form one unit. In the same way, each unit is mutually lapped in order to form a given column line type sheathing wall.