PURPOSE: To prevent a buried pipe from being damaged by the cutter of a drilling machine.
CONSTITUTION: A band body 13 is arranged with wires 14 at an appropriate interval such that the wires 14 are conducted in the longitudinal direction of the band body 13 to constitute a long monitoring body 12 which is then buried in the vicinity of an object to be monitored, i.e., a buried pipe 11. A resonance characteristics measuring apparatus 16 for the wire 14 is disposed on one end side of the long monitoring body 12 and an AC monitoring signal is inputted while sweeping the wire 14 from one end side thereof thus measuring the resonance frequency of the wire 14 and monitoring the cut-off of the wire 14 due to damage of the long monitoring body 12 based on a resonance frequency. Since a damage alarm signal of the buried pipe 11 can be delivered at a moment when the cutter of a drilling machine approaches the buried pipe 11, the buried pipe 11 can be protected against damage.
SUYAMA KENJI
IMAOKA TAKASHI
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