| 摘要 |
Three bow shaped steel profiles (1,3) are assembled in order to serve as a tubbing in combination with transversally positioned wooden bars (5,17), which are held with their ends inside the profiles (4). The installation is facilitated by using pre-assembled units of profiles (1,3) and wooden bars (5,17), which are linked with steel, textile, or synthetic belts (18). The bars (17) can still be moved longitudinally if required. The profiles (1,3) can also be moved before they are fixed with a clamping unit (19) in their final position without being affected by the assembled wooden bars (5,17). A plastic foil can be attached to the outer surface of the unit, protecting the inner area of the tunnel from intruding dust.
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