Abstract: An object of the invention is to realize a backfill structure suitable for relatively small-scaled land improvement without causing such a problem that a retaining wall after construction is unstable. A backfill structure for constructing an underground structure is composed of a plurality of wall face panels 1 vertically provided on a front face of a ground portion, coupling members 2 which are inserted through through-holes provided in the wall face panels to be fastened on the front face side of the wall face panels, net-like sheets 3 fastened with the other ends of the coupling members 2, and backfill soil body which is filled on the net-like sheets 3 to bury and fix the net-like sheets 3, where the backfill soil body is filled between the wall face panels 1, the back face side of the wall face panels, and the ground portion.

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.

Abstract: An object of the invention is to provide a retaining wall and a construction method therefor whereby fixation between a steel sheet pile wall and a formwork panel to form the retaining wall is made easy, and can be reliably made, so that construction schedule reduction is achieved. The retaining wall is composed of steel sheet piles 100 driven in the ground preliminarily, a formwork panel 201 fixed in close contact with a face of the steel sheet piles 100 opposite to a ground region, and a formwork panel 202 vertically provided at a position facing the formwork panel 201. The formwork panels 201 and 202 are vertically provided on runners 204 fixed preliminarily to the ground by screws 203, and have caps 205 on their tops to maintain horizontal states and linear states of the formwork panels 201 and 202.