| 摘要 |
PROBLEM TO BE SOLVED: To provide a secondary lining structure on an internal surface of a tunnel, which facilitates arrangement of boards on the internal surface of the tunnel. SOLUTION: An engaging member 52 having a shaft portion 50 and a head portion 51 is attached onto the internal surface of the tunnel by means of its shaft portion 50. Then, the engaging member 52 is inserted into a hole portion 56 formed in a board B, and thereafter the board B is slid, whereby the shaft portion 50 is moved in an engaging groove 55 sequentially formed in the hole portion 56. Further, the head portion 51 is engaged with an engaging surface portion 58 on a rear side of the engaging groove portion 55.
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