PURPOSE:To know the piping state of a buried pipe speedily and securely by digging plural small holes reaching the buried pipe and installing an oscillator and an oscillation measuring instrument. CONSTITUTION:A small hole 9 for inspection and meter installation is digged at a point where it is evident on the ground surface that the buried pipe 1 is present, and the piping direction and depth for the pipe 1 are known to dig a hole 3 in the direction, e.g. 100m ahead. Then the oscillation measuring instrument 11 is installed on a pipe 11 exposed in the small holes 9 and 3 at one hole position and the oscillator 12 is installed at the other; and the pipe 1 is vibrated to know the burying state of the pipe 1 from the waveform and propagation time of the vibrations. When it is found that the holes 9 and 2 are on a straight line, a small hole 4 is digged similarly further about 100m ahead to know the state of the pipe 1. This operation is repeated to estimate that the pipe 1 in this section is bent from measurement results at the points of the small holes 4 and 5, and small holes 6 and 7 are digged in this section to take a measurement again. Thus, the rough piping state is grasped and then a small hole 10 is digged at a proper point to confirm the piping position, thereby knowing the piping state speedily and accurately.
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