| 摘要 |
PROBLEM TO BE SOLVED: To provide an underground structure cover capable of finely maintaining nonslip efficiency for a long period of time irrespective of installation environment by optimizing an arrangement pattern of projections provided on the surface of a cover main body and shapes of the projections. SOLUTION: In an underground structure cover for uniformly arranging respectively independent projections 4a, 5a and 6a on the surface of a cover main body 3, and small projections 4b, 4c, 5b, 5c and 6b are formed on the upper surfaces of parts or the whole among the projections. The small projections 4b, 4c, 5b, 5c and 6b on the highest stage and the projections forming no small projection on them having the size of the top surfaces of them can be stored in the circle with a diameter of 25 mm, and at least one of their shortest intervals between the outlines of the projections 4a, 5a and 6a or the small projections 4b, 4c, 5b, 5c and 6b and outlines of the projections 4a, 5a and 6a adjacent to them or the small projections 4b, 4c, 5b, 5c and 6b becomes 10-30 mm. |
