| 摘要 |
<p>PROBLEM TO BE SOLVED: To prevent a lined underground buried article from being damaged by boring or the like. SOLUTION: In a damage preventive device for a lined underground buried article, a high hardness ceramic plate 12 or a fiber-reinforced plastic plate is claded on a protective iron plate 10. When a cutting edge 23 abuts on the ceramic plate 12 or plastic plate, idle sliding is caused or the fibers are wound round the cutting edge 23 so that the cutting edge 23 cannot be advanced further. Thereby, the existence of the lined underground buried article is found, so that the damage can be prevented. Further, a rotating speed or advancing speed detecting sensor 24 is fitted to the cutting edge 23 of a boring machine 20, and when the speed becomes below a prescribed value, boring is stopped or an alarm is output by a control circuit 25.</p> |
