To prevent underground water from springing up into an opencut hole easily and positively at the time of inserting a pipe into the ground from the open-cut hole.
A part of an earth retaining wall 12 is cut off, and the ground 13 on the inner side is manually dug by the specified depth in the horizontal direction to form a pre-excavated part 14. Freezing jigs 21 are installed in the pre-excavated part 14. A steel plate 22 of the freezing jig 21 is formed in almost half-ring shape in conformity to the periphery of a pipe roof steel pipe 31. Flow velocity resistance material 24 is disposed at the inner peripheral surface of the steel plate 22, and a freezing pipe 25 is piped on the outer peripheral surface. When liquid nitrogen is led into the freezing pipe 25, a part around the freezing jig 21 is locally cooled to form a frozen area R. When underground water in the ground 13 flows into the pre-excavated part 14, the underground water is captured into this frozen area R and frozen so as to prevent water from spring up into an open-cut hole 11 from a pipe roof steel pipe start part 20.
SAKAGUCHI KATSUHIKO
MIWA HARUFUMI
MITSUISHI KAZUNARI
MIZUTA TOMOYUKI
