| 摘要 |
<p>The safety equipment is for use with tunnels, to give early warning of a possible cave-in, and comprises aluminium sheets covering the tunnel walls. The high degree of reflectivity of aluminium immediately reveals any distortion. The thickness of the aluminium depends on the strength required, and the sheets can be secured by steel foundation bolts. The sheets may be illuminated from a locomotive travelling through the tunnel, so as to detect any distortion indicating the start of a cave-in.</p> |
