| 摘要 |
PROBLEM TO BE SOLVED: To provide a cover for an underground structure securing required mechanical strength while suppressing the weight increase of the cover. SOLUTION: A reinforcing rib 7 provided on the back face side of a plate part 3 is composed of a longitudinal rib 11, a lateral rib 15, a first inclined rib 17 extending parallel with one diagonal line of the cover 1 for a manhole, and a second inclined rib 19 extending parallel with the other diagonal line. Both diagonal parts of a rectangular enclosure part 21 formed by the longitudinal ribs 11 and lateral ribs 15 are respectively connected by the first inclined rib 17 and the second inclined rib 19.
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