To reduce cost by constituting an underground unit structure in such a manner that columnar soil is lapped and driven into a pit excavated to a ground and a single pipe is inserted to columnar soil as a core material.
Columnar soil 3 is prepared by agitating an auger, injecting cement milk into a pit 2 excavated to a ground 1, and an earth retaining wall 5 is formed by lapping and driving columnar soil 3 while inserting a single pipe 4 into columnar soil 3 as a core material. The earth retaining wall 5 and the base of the pit 2 are covered with a waterproof sheet bag 6 and laid in, and fixed partially at an end section 6a, and concrete is placed on the base of the waterproof sheet bag 6 and a floor slab 7 is formed. An underground unit 9 is arranged so as to form a static air layer 8 between the unit 9 and the waterproof sheet bag 6 being placed on the floor slab 7 while covering the earth retaining wall 5. Accordingly, since the earth retaining wall 5 is used as a permanent structure, the underground unit structure is built temporarily for constructing an underground exterior wall, and cost can be made smaller than a construction method in which the underground exterior wall is built and removed.
HAYASHI SHINICHI
KONDO SHINICHI
AZUMA TETSUYA
