Abstract: An architecture unit of a concrete structure is formed by providing a pair of wall bodies facing each other substantially in parallel with each other on a foundation. The wall bodies are each composed of a porous steel-made formwork panel having large and small ribs formed on a surface thereof, a runner provided with a fitting groove fitted with lower ends of a plurality of formwork panels arranged side by side, and a cap fitted with upper ends thereof. A long-plate-like lower fixing member provided with ribs at both ends thereof is spanned and fixed on a lower face of the runner so as to be substantially perpendicular to the runner, and a long-plate-like upper fixing member provided with ribs at both ends thereof is spanned and fixed on a top face of the cap so as to be substantially perpendicular to the cap.

Abstract: [Problem] An object of the present invention is to provide a construction method for a new underground structure, the method achieving reduction in the load imposition of a new underground framework on an existing underground concrete framework, and reduction in construction cost for constructing the new underground structure. [Solving Means] A new underground structure 100 having a basement available as a residential space, and an underground pit which is an underground facility for housing piping equipment, etc., is constructed with a fluidized soil wall 300 held between an existing underground concrete framework 200 and a new underground concrete framework 400.