| 摘要 |
When the final tunnel vault component, the keystone, is fitted in a tunnel vault, high frictional forces occur between its profiled jointing strips and those of the tubbing already fitted, which can move the profiled jointing strips in their longitudinal grooves. Therefore each of the adjacent contact surfaces of the profiled jointing strips are given a coating (10) of harder material with a lubricant which diffuses at the surface. In addition to this measure, which prevents the profiled jointing strips from moving, said strips are also anchored in their joints by means of anchoring ribs (15) which engage with the walls of the groove (5) and thus, together with the lubricant applied, also prevent the strips from moving longitudinally.
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