Patent ID: 8408844

Claim:
An underground continuous wall structure comprising a plurality of steel materials, wherein each of the steel materials comprises a hat type steel sheet pile having a hat-shaped vertical cross-section with respect to a length direction thereof, and a single H-beam having an H-shaped vertical cross-section with respect to a length direction thereof; the hat type steel sheet pile comprises a single web, a pair of flanges connected integrally to each end of the single web and inclined so as to spread outward, and a pair of arm sections substantially parallel to the single web which are each connected integrally to one of the pair of flanges; the single H-beam comprises a pair of flange sections substantially parallel to each other, and a web section which connects the pair of flange sections to each other leaving space therebetween; an outer surface of one of the pair of the flange sections of the single H-beam on an opposite side to a surface of the one of the pair of flange sections of the single H-beam which connects to the web section is secured by welding to an outer surface of the single web of the hat type steel sheet pile, the outer surface of the single web of the hat type steel sheet pile being on an opposite side to a channel formed by the single web and the flanges of the hat type steel sheet pile; a longitudinal length of the single H-beam is shorter than a longitudinal length of the hat type steel sheet pile; a rear end of the single H-beam is located closer to a forward end side in the length direction of the hat type steel sheet pile than a rear end of the hat type steel sheet pile; a forward end of the single H-beam is located closer to a rear end side than a forward end of the hat type steel sheet pile in the length direction; a separation length between the for forward end of the hat type steel sheet pile and the forward end of the single H-beam is not less than 5% and not more than 30% of an overall length of each of the steel materials in the length direction of the hat type steel sheet pile; a joint is formed in a first end of each of the pair of the arm sections on an opposite side to a second end of each of the pair of the arm sections which is connected integrally to each of the pair of flanges, the joint including an engagement claw section; a groove is formed in the joint so that the engagement claw section is located at the first end, and a shape of the groove is substantially the same as a shape of the engagement claw section in the hat-shaped vertical cross-section; the plurality of the steel materials is disposed so that a separation length between the rear end of the hat type steel sheet pile and the rear end of the single H-beam is not less than 10% and not more than 50% of a wall height from a planned ground level to a ground surface in the underground continuous wall structure; and the forward end of the single H-beam of each of the steel materials is disposed in a ground.