STEEL PIPE WELDING METHOD, STEEL PIPE WELDING-BURYING DEVICE AND EARTH RETAINING CONSTRUCTION METHOD BY WELDED STEEL PIPE

PURPOSE: To enhance the strength of the connected parts of steel pipes and reduce cost required for the steel pipes in an earth retaining construction method by steel pipes. CONSTITUTION: In an earth retaining construction method by welded steel pipes, plural steel pipes 7... are driven in almost along the axial direction of a tunnel 14 to be excavated in such a way as to cover the outer peripheral upper side of the tunnel 14. The steel pipes 7.. are to be long-sized ones connected by welding. At the time of welding the steel pipes 7..., the steel pipes 7 are made butt each other, and cylindrical backing material is applied to the butt parts of the steel pipes 7... At the time of applying the cylindrical backing material, only the half of the backing material is inserted into one steel pipe 7 between the steel pipes 7, 7 to be welded. The remaining half of the backing material extended out from one steel pipe 7 is inserted into the other steel pipe 7, and the mutual joint end parts of the steel pipes 7, 7 are made butt each other with a slight clearance. Welding is then performed from the outer face side of the steel pipes 7.