JP3386367B2 - Surface displacement detector - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface layer displacement detection for detecting a small displacement of a surface layer (slope) in an area where there is a danger such as a landslide with a high accuracy from a remote point, for advance prediction and warning of a landslide disaster. Regarding the device.

[0002]

2. Description of the Related Art Generally, a micro-displacement on the surface of the surface layer occurs before a large-scale landslide. By detecting this small displacement, it is possible to predict and warn about a disaster. For this purpose, various measuring methods have been tried, but an example in practical use will be described with reference to FIG. 11.

In FIG. 11, 1 is a safe immovable area, 2
Is a dangerous area where a landslide in the direction of arrow P is predicted, and 3 is a crack or a terrain conversion point at the boundary between both areas. 4 is a pile driven into the dangerous area 2, 5 is a base fixed to the immovable area 1 near the boundary 3, and 6 is an extensometer installed on the base 5. Reference numeral 7 denotes an invar wire, which is stretched by connecting the pile 4 and the extensometer 6. This invar wire 7 is a special steel wire made of nickel alloy having a diameter of 0.5 mm, has a very small temperature coefficient, and is hardly affected by the temperature and sunshine. 8 is Invar line 7
Is a protective cover made of a wood gutter or a vinyl chloride pipe that is fixed by a support member 9 to cover the.

The extensometer 6 incorporates a winding wheel for winding the invar wire 7, a chart type recorder and a clock. The expansion and contraction of the invar wire 7 caused by the displacement of the surface layer causes the rotational displacement of the winding wheel. This displacement is linked to the pen of the chart recorder via the magnifying mechanism, and the surface layer displacement corresponding to the time is recorded on a daily or weekly basis. The recorder has a contact mechanism that operates when a displacement of a certain value or more occurs, and an alarm can be issued by a buzzer placed at an appropriate position by the operation of this contact.

[0005]

The conventional surface layer displacement detecting device based on such expansion and contraction of the invar wire 7 can detect a minute displacement of a few mm of the surface layer, but the following problems occur. Was there. (1) The work for precisely laying the invar wire 7 in the dangerous area 2 is required, the installation cost of the device is high, and the danger due to on-site work is also large. (2) Since there is a restriction on the length of the Invar wire 7, the extensometer 6
Since the installation location of is limited to the vicinity of the boundary 3 of the dangerous area 2, it is difficult to measure from a sufficiently safe remote point. Therefore, there is a risk in maintenance work such as collection and replacement of recording paper. (3) When the dangerous area 2 is a steep slope or a cliff, necessary erection work cannot be performed, and the surface layer displacement cannot be detected by this means. (4) The surface layer displacement is detected by the change in the physical length of the invar wire 7, and it is inappropriate to use it as a sensor of an alarm / prediction system that takes in the displacement as electronic information. (5) It is difficult to make the entire apparatus into a compact and easily movable unit configuration, and mobility is lacking. The present invention has been made under such a background, and detects small displacements of the surface layer (slope) at risk of landslides with high accuracy from a safe remote point for advance prediction and warning of landslide disaster. An object of the present invention is to provide a surface layer displacement detection device that can be used.

[0006]

SUMMARY OF THE INVENTION The present invention has been made for the purpose of solving the above-mentioned problems. The invention according to claim 1 is to provide a monitor means fixed in a fixed area and a predetermined distance from the monitor means. And a radio wave reflection means fixed in a dangerous area, the monitor means transmitting a radio wave of a predetermined wavelength (λ) toward the radio wave reflection means, and a reflection from the radio wave reflection means. A receiving means for receiving the wave, a mixer means for combining the transmitting wave and the receiving wave in the receiving means, and a displacement within λ / 4 of the anti-radiation means for the minimum level of the output amplitude of the composite wave of the mixer means. And a level detecting means for detecting a change in the maximum level. Further, the invention according to claim 2 is formed on the monitor means fixed to the immovable area, the radio wave reflecting means fixed to the dangerous area at a predetermined distance from the monitor means, and the radio wave reflecting means. The monitor means comprises a periodically varying means of reflectance, the monitor means transmits a radio wave of a predetermined wavelength (λ) to the radio wave reflection means, and a reception means receives the reflected wave from the radio wave reflection means. A mixer means for synthesizing the transmitted wave and the received wave in the receiving means, an envelope detecting means for extracting a variable period component from a combined wave output of the mixer means, and a displacement within λ / 4 of the radio wave reflecting means. Is detected as a change in the envelope output amplitude from the minimum level to the maximum level. Also,
According to a third aspect of the present invention, there is provided a monitor means fixed to the immovable area, and a radio wave reflection means fixed to a dangerous area separated by a predetermined distance from the monitor means. Transmitting means for transmitting a radio wave having a predetermined wavelength (λ) amplitude-modulated at a constant cycle toward the means, receiving means for receiving a reflected wave from the radio wave reflecting means, and the transmitting wave and the receiving wave in the receiving means. Mixer means for synthesizing, and envelope detection means for extracting the modulated wave component of the constant period from the synthesized wave output of the mixer means,
Level detecting means for detecting a variation within λ / 4 of the radio wave reflecting means as a change from the minimum level to the maximum level of the envelope output amplitude.
Further, the invention according to claim 4 comprises a monitor means fixed to the immovable area and a radio wave reflecting means fixed to a dangerous area separated from the monitor means by a predetermined distance. Transmitting means for transmitting a radio wave of a predetermined wavelength (λ) amplitude-modulated at a constant cycle toward the radio wave reflecting means, and a reflected wave from the radio wave reflecting means which is separately installed in the fixed place apart from the transmitting means. Receiving means, mixer means for synthesizing the transmitting wave and the receiving wave in the receiving means, envelope detecting means for extracting the modulated wave component of the constant cycle from the synthesized wave output of the mixer means, and the transmission means. Level detecting means for detecting a variation within λ / 4 of the OR reflecting means as a change from the minimum level to the maximum level of the envelope output amplitude. The invention according to claim 5 is the ground surface displacement detecting device according to any one of claims 1 to 4, characterized in that a Luneberg lens means is used as the radio wave reflecting means.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will now be described in more detail with reference to the drawings. FIG. 1 is an overall configuration diagram of a surface layer displacement detection device according to a first embodiment of the present invention. Reference numerals 1 to 4 are the same as the constituent elements described in FIG. Reference numeral 10 is a monitor means fixed to an immovable area 1 (safety area) via a support 11, and 12 is this monitor means 1.
It is a transmitting / receiving antenna that is integrally formed in the housing of 0.

Reference numeral 13 is a radio wave reflection means fixed to the top of the pile 4 driven into the surface layer displacement area (danger area 2), L
Indicates the distance between the radio wave reflecting means 13 and the transmitting / receiving antenna formed on the monitor means 10. The monitoring means 10 transmits a transmission wave of frequency F (for example, 10G) via the transmission / reception antenna 12.
(Microwave of Hz) ft in the form of a beam
The reflected wave fr from the radio wave reflection means is received again via the transmission / reception antenna 12 and is combined with the transmitted wave ft.

Considering that the phase is inverted when the transmitted wave ft is reflected by the radio wave reflection means 13, 2L = (1/2). (N + 1) .lambda. (.Lambda .: wavelength .lambda. =
C / F C: speed of light), the transmitted wave ft and the reflected wave fr are in phase at the position of the monitor means 10, and the combined amplitude is the sum of the two. On the other hand, 2
When L = (n / 2) λ, the transmitted wave ft and the reflected wave fr have opposite phases, and the combined wave has a difference between them.

Therefore, when the combined amplitude V of the transmitted wave ft and the reflected wave fr is taken, it becomes a sine wave that changes from the maximum value to the minimum value during λ / 4 as shown in FIG. For example, if the distance between the monitor means 10 and the radio wave reflection means 13 is set in advance so that the point A (voltage VA) in FIG.
The operating point is B point (VB), C
It changes to a point (VC) and the moving distance can be detected from the change value of the combined amplitude. In other words, this converts the relative phase of the reflected wave fr into a voltage.

Here, for example, F = 10.525 GHz
(Λ = 28.5 mm), λ / 4 = 7.12 mm. During this period, the combined amplitude changes from the maximum value to the minimum value (full scale), so that it is possible to detect a distance change of about 3 mm (1/8 full scale) of 1 mm in the measurement resolution of this amplitude.

FIG. 3 shows a fine movement adjustment for moving the monitor means 10 by a minute distance (ΔL) in the transmission / reception wave direction in order to preset the operating point (A, B, C) which becomes a reference according to the predicted direction of the surface layer displacement. It is a structural example in which the mechanism 14 is provided. As is clear from the above description, the displacement detecting device according to the first embodiment of the present invention focuses on the relative phase and converts it into a voltage, and therefore cannot measure displacement exceeding λ / 4. Therefore, when the frequency of 10.525 GHz is used, since λ / 4 = 7.12 mm, the fine adjustment mechanism 14
An adjustable distance of 10 mm is sufficient.

FIG. 4 is a block diagram showing the electrical construction of the monitor means 10. A microwave oscillating unit 15 oscillates a microwave having a predetermined frequency F and supplies it to the coupler 17 via the buffer amplifier 16. Coupler 1
Reference numeral 7 is for dividing the microwave into two, one of which is supplied to the circulator 19 via the power amplifier 18 and the other of which is supplied to the mixer 20. The circulator 19 is a switch, and supplies the microwave supplied from the power amplifier 18 to the antenna 12 and the received microwave supplied from the antenna 12 to the mixer 20.

The antenna 12 transmits and receives microwaves, and the microwave ft transmitted in a beam form from the antenna is reflected by the radio wave reflection means 13, and the reflected microwave fr is received by the same antenna 12. Is
It is supplied to the mixer 20 via the circulator 19.

The mixer 20 receives the transmission wave f from the coupler 17.
t (microwave) and reflected wave f from the circulator 19
r (received microwave) is combined, and the DC level V of the combined amplitude is λ / of the radio wave reflection means 13 as described in FIG.
It changes from the maximum to the minimum due to the phase difference between the transmitted wave ft and the reflected wave fr (reception microwave) due to fluctuations within 4.

Reference numeral 21 is a DC amplifier for amplifying the DC component of the composite amplitude V and setting the span, and its output V0
Is set to change within a range of 1 to 5 volts with respect to a change of 0 to λ / 4 of the radio wave reflection means 13, for example.

Reference numeral 22 is a signal processing unit, which uses the DC amplifier output V0 as an input signal, and outputs an alarm by comparison with an alarm set value, a daily change record or a weekly change record, and digital conversion if necessary. After that, more complicated data management is executed by computer processing. Reference numeral 23 denotes an on-site indicating instrument which operates at the output of this signal processing unit, and S denotes an output of this signal processing unit 23 which is an analog or digital transmission signal which is transmitted to a remote monitoring center or the like.

Next, a second embodiment of the present invention will be described with reference to FIGS. Since the radio wave reflecting means 13 is limited in practical size, the reflected wave fr is extremely weak as compared with the transmitted wave ft. In addition, reflection naturally occurs not only from the reflector but also from the surrounding soil and sand, trees, etc. Considering the movement of water flow, gravel, etc., there is always a fluctuation of about 1 mm. As a method of extracting only the reflected wave from the installed radio wave reflection means 13 excluding the influence of these backgrounds, in the second embodiment, the reflection means is modulated to remove the background noise in the frequency domain. It has a feature.

FIG. 5 is a side view of the radio wave reflection means 13,
The radio wave reflecting sphere body 24 is mainly composed of a lens member made of expanded polystyrene. Reference numeral 25 is a hemispherical metal reflector which is attached to cover the back surface of the radio wave reflecting sphere body 24. The radio wave reflecting sphere body 24 having such a configuration is a known technical means that is used as a radar radio wave reflecting means for confirming the position of a buoy on the sea by a radar and is commonly used as a so-called Luneberg lens.

Numeral 26 indicates a transmitted wave ft on the surface of the metal reflection plate 25.
A plurality of slots are formed parallel to the plane of polarization of. FIG. 6A is a plan view showing one of the slots 26 taken out. The length of the slot 26 is set to λ / 2, and short-circuiting is performed across the slots at the intermediate position, that is, the λ / 4 position. As shown in FIG. 6 (B), the PIN diode 27 is connected in high frequency through the chip capacitor means 28.

Reference numeral 29 designates the PIN diode 27 as an alternating current signal fm.
It is a signal source for modulation that periodically performs switching control.
Since the PIN diode 27 is periodically on / off controlled at the frequency of the modulation signal source 29, as shown in FIG.
Slot 26 is shown in FIG. 7 when PIN diode 27 is on.
As in (A), it is equivalently divided into two slots, that is, a slot 26a and a slot 26b of λ / 4, and the slot length is λ / 2 in the off state. In the mode of FIG. 7A in which the slot is equivalently divided into two, the incident radio wave is reflected in the incident direction, so the reflection amount is large. On the other hand, in the mode of FIG. 7B in which the slots are not divided, the incident radio waves pass through the slots 26, so the amount of reflection is drastically reduced. By such switching control of the PIN diode 27,
The reflected wave fr is an intermittent wave that is switching-modulated with the AC signal fm as shown in FIG.

The frequency of the modulating AC signal fm is set to be sufficiently higher than the frequency of the sand and gravel fluctuation caused by the fluctuation of the tree due to the wind and the change of the rainwater flow, and the component modulated by the signal fm from the composite wave by the filter means. Can be extracted to obtain a fluctuation signal of only the radio wave reflection means in which background noise is cut. According to this method, it is possible to remove the influence of the amplitude fluctuation of the transmitted wave ft.

FIG. 8 shows an example of the structure of the monitor means 10 when the radio wave reflection means is modulated. The same elements as those in the configuration described with reference to FIG. 4 are designated by the same reference numerals, and the description thereof will be omitted. A high frequency amplifier 30 amplifies an alternating current component of the composite wave output of the mixer 20. Reference numeral 31 is a bandpass filter having a center frequency of the modulated AC signal fm, and extracts the envelope signal ve of the signal that is modulated at the frequency of the modulated AC signal fm from the composite signal.

Reference numeral 32 denotes a rectifying / smoothing circuit for the envelope signal ve, which converts the envelope signal ve into a DC signal v proportional to the amplitude of the envelope signal ve. The configurations of 21 to 23 are the same as in the case of FIG. FIG. 9 shows that the movement of the radio wave reflection means due to the phase difference of the composite wave can be measured in exactly the same way as in FIG. 2 by the change of the amplitude v of the envelope signal of the received wave modulated by the modulated AC signal fm. There is.

As in this embodiment, in the method of modulating the reflected wave on the side of the radio wave reflection means, a power supply means is used for driving the signal source for switching the PIN diode 27 which short-circuits the slot of the Luneberg lens. There is a problem you need. However, since the power for switching the PIN diode may be an extremely weak current, by providing a solar cell and a simple battery means on the radio wave reflecting means side 13 side, this problem can be solved without providing a cable means for power supply. It is possible to eliminate it.

Next, a third embodiment of the present invention will be described with reference to FIG. The feature of this third embodiment is to simplify the configuration of the radio wave reflection means by applying modulation on the transmission side, and is suitable for an environment with a small background noise around and a good reflected wave to noise ratio. There is. Further, the third embodiment is characterized in that the monitor means 10 is separated into a transmitting unit and a receiving unit.

In FIG. 10, 10a is a transmission unit,
10b shows a receiving unit. In the transmission unit 10a, 33 is a modulation circuit, which amplitude-modulates the output of the microwave oscillating unit 15 with a signal of 10 kHz, for example. Therefore, the transmission wave ft from the transmission antenna 12a is 10
The microwave is amplitude-modulated by KHZ. 16, 18
Are the same as those in FIGS. 4 and 8.

In the receiving unit 10b, the receiving antenna 12b has a reflected wave fr from the radio wave reflection means 13 and a direct wave f that wraps around the ground from the transmitting antenna 12a.
t ′ is received and combined by a linear element 34 such as a diode to generate a combined wave fm. Subsequent processing is exactly the same as in FIG. 8, and a minute fluctuation can be measured by the amplitude v of the envelope signal ve of the modulation frequency.

[0029]

As described above, in the apparatus of the present invention characterized by using the radio wave means, the following effects can be expected as compared with the conventional system. (1) The construction work in the hazardous area is only the installation of the radio wave reflection means, there is no need for the construction work of precision installation of the Invar wire as in the past, the installation cost of the device is small, and it is necessary to enter the site. The risk is small. (2) Since radio waves are used, the monitor means can be installed in a safe area by separating (100 m or more) from the boundary of the dangerous area, and there is no danger in collecting and maintaining data. (3) The installation of the radio wave reflection means requires only one stake, so it is possible to install the necessary monitoring system even when the dangerous area is a steep slope or a cliff. (4) Since ground surface displacement is converted into electronic information such as voltage signals, it has versatility in data processing and use, and is optimal as a sensor for disaster warning / prediction systems. (5) It is easy to make the entire device into a unitized structure that is compact and easy to move, and is excellent in maneuverability.

[Brief description of drawings]

FIG. 1 is an overall configuration diagram of a surface layer displacement detection device according to a first embodiment of the present invention.

FIG. 2 is a characteristic diagram showing a level change of a composite wave of a transmission wave and a reception wave in the first embodiment.

FIG. 3 is a side view showing a fine adjustment mechanism 14 of the monitor means 10 in the first embodiment.

FIG. 4 is a block diagram showing an electrical configuration of the monitor means 10 in the first embodiment.

FIG. 5 is a side view of a radio wave reflection means 13 using a Luneberg lens according to a second embodiment of the present invention.

FIG. 6 is a configuration diagram of a PIN diode 27 for controlling a slot length of a Luneberg lens.

FIG. 7 is an explanatory diagram showing switching of apparent lengths of slot lengths of a Luneberg lens.

FIG. 8 is a block diagram showing an electrical configuration of monitor means in the second embodiment.

FIG. 9 is a characteristic diagram showing a change in amplitude level of a modulated wave envelope of a synthetic wave in the second embodiment.

FIG. 10 is a block diagram showing an electrical configuration of monitor means in the third embodiment of the present invention.

FIG. 11 is an overall configuration diagram showing an example of a conventional surface layer displacement detection device.

[Explanation of symbols]

1 immovable area 2 dangerous areas 3 boundaries 4 piles 10 Monitor means 11 Support 12 transmitting and receiving antenna 13 Radio wave reflection means 15 Microwave oscillator 16 buffer amplifier 17 Couplers 18 power amplifier 19 Circulator 20 mixer 21 DC amplifier 22 Signal processing unit 23 Field indicator

─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP 10-20017 (JP, A) JP 60-119409 (JP, A) JP 10-68774 (JP, A) Actual 63- 67891 (JP, U) (58) Fields surveyed (Int.Cl. ⁷ , DB name) G01D 21/00 G01B 21/00 G01C 15/00 G01S 13/36

Claims (5)

(57) [Claims] 1. A monitor means fixed to an immovable area, and a radio wave reflecting means fixed to a dangerous area at a predetermined distance from the monitor means, wherein the monitor means faces the radio wave reflecting means. Transmitting means for transmitting a radio wave of a predetermined wavelength (λ), receiving means for receiving the reflected wave from the radio wave reflecting means, mixer means for synthesizing the transmitted wave and the received wave in the receiving means, and the radio wave counter And a level detecting means for detecting a displacement of the injection means within λ / 4 as a change of the composite wave output amplitude of the mixer means from a minimum level to a maximum level. 2. A monitor means fixed to an immovable area, a radio wave reflecting means fixed to a dangerous area at a predetermined distance from the monitor means, and a periodically variable reflectance formed on the radio wave reflecting means. The monitor means includes a transmitting means for transmitting a radio wave of a predetermined wavelength (λ) toward the radio wave reflecting means, a receiving means for receiving a reflected wave from the radio wave reflecting means, and a receiving means in the receiving means. Mixer means for synthesizing the transmitted wave and the received wave, envelope detecting means for extracting a variable period component from the synthesized wave output of the mixer means, and displacement of the radio wave reflecting means within λ / 4 for the minimum envelope output amplitude. And a level detecting means for detecting a change from the level to the maximum level. 3. A monitor means fixed to an immovable area, and a radio wave reflection means fixed to a dangerous area at a predetermined distance from the monitor means, wherein the monitor means faces the radio wave reflection means. Transmitting means for transmitting a radio wave having a predetermined wavelength (λ) amplitude-modulated at a constant cycle, receiving means for receiving the reflected wave from the radio wave reflecting means, and the receiving wave for synthesizing the transmitted wave and the received wave. The mixer means, the envelope detecting means for extracting the modulated wave component of the constant cycle from the composite wave output of the mixer means, and the fluctuation within λ / 4 of the radio wave reflecting means are controlled to have a maximum level higher than the minimum level of the envelope output amplitude. A surface layer displacement detecting device, comprising: a level detecting means for detecting a change. 4. A monitor means fixed to an immovable area, and a radio wave reflecting means fixed to a dangerous area at a predetermined distance from the monitor means, wherein the monitor means faces the radio wave reflecting means. Transmitting means for transmitting a radio wave having a predetermined wavelength (λ) amplitude-modulated at a constant cycle; and receiving means separately installed on the immovable ground and independently for receiving the reflected wave from the radio wave reflecting means. Mixer means for synthesizing the transmitted wave and the received wave in the receiving means, an envelope detecting means for extracting the modulated wave component of the constant period from the combined wave output of the mixer means, and λ / of the transmission OR reflecting means. And a level detecting means for detecting a variation within 4 as a change of the envelope output amplitude from the minimum level to the maximum level. 5. The surface layer displacement detecting device according to claim 1, wherein a Luneberg lens means is used as the radio wave reflecting means.