| 摘要 |
<p>The arch stones (3,4) which are combined in pairs have respective their mutual circumferential edges (12,13) placed side by side relative to the tunnel longitudinal axis. These edges are longitudinal but have a localised zone (17), in a longitudinal direction, having edge positioning parts (39,51). One part comprises a longitudinal fork (39) ) having two longitudinal teeth (41) defining between them a longitudinal slot (40) which is open in the longitudinal direction (2). The other part is a tenon (51) which is gripped by the fork by engaging the tenon in the slot. The tenon forms a projection relative to the edge (13) and the positioning fork is withdrawn relative to the edge and housed in a pocket (18)</p> |
