| 摘要 |
PROBLEM TO BE SOLVED: To detect a minute displacement of a ground surface as it has a danger of landslide from a safe remote point with high precision by comprising a monitor means fixed to a steady area and a radio reflecting means fixed within a danger area. SOLUTION: This surface layer displacement detecting device is provided with, for example, a monitor means 10 having a transmitting and receiving antenna 12, which is fixed to a steady area 1 through a support base 11, and a radio reflecting means 12 such as a Luneberg lens, which is fixed to a pile 4 driven into a surface layer displacing area 2. The monitor means 10 transmits a transmitting wave ft which is a micro wave having a prescribed wavelengthλin beam form, receives the reflected wave fr from the reflecting means, and composes it with the transmitting wave ft. Since the amplitude of the composed wave is changed from the maximum value to the minimum value withinλ/4, the distance between the monitor means 10 and the reflecting means 13 is properly preset, whereby a minute moving distance can be detected. In order to remove the background noise, the reflected wave may be modulated by the reflecting means 13.
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