PURPOSE: To reduce the manufacturing cost of a segment and reduce the excavation sectional surface in the shield excavation, by firmly connecting segments so that the bending strength and bending rigidity increase and by reducing the weight of the segment.

CONSTITUTION: At the front end part of one segment 2 which constitutes a segment ring 1, a groove-shaped metal fitting 4 which projects towards the front part of the other segment 3 is fixed. At the rear end part of the other segment 3, a groove-shaped metal fitting 5 which projects toward the rear end part of one segment 2 is fixed. At the front end part of the other segment 3, a shaft metal fitting 6 arranged in the groove-shaped metal fitting 4 is fixed, and the part between the groove-shaped metal fitting 4 and the shaft metal fitting 6 is charged with the material 10 which hardens through the lapse of time, and the part between the groove-shaped metal fitting 5 and a shaft metal fitting 7 is charged with the material 10 which hardens through the lapse of time.