JPH04286983A - Underground buried object searcher - Google Patents

Abstract

PURPOSE:To identify the existence of a buried pipe and specify its laying direction even in the case where a reflected wave group does not have hyperbola-like continuity by converting a reflected signal from the buried pipe into a frequency area to calculate a spectral distribution. CONSTITUTION:An electromagnetic wave is transmitted into the underground 4 from a transmission antenna part 1 and the reflected wave from a buried pipe 5 and the like are received by a receiving antenna part 2. A received observation signal is sampled 11, the sampled signal is converted into a frequency area in a waveform analyzer 12, a spectral distribution is calculated, and a reflected image of the buried pipe 5 is identified on the basis of a spectrum peak frequency, a direct current component ratio and half-value width. Next, the antenna part 2 alone is moved along its laying direction right above the identified pipe 5, the reflected wave is sampled 11 at specified intervals, and the reflected signals alone from the pipe 5 are extracted by the device 12. Next, the change of a propagation delay time of the reflected wave from the pipe 5 corresponding to the movement distance of the antenna part 2 is examined in a calculation part 14, the dielectric constant of the underground 4 is found and buried depth is calculated on the basis thereof.

Description

Description: [0001] The present invention relates to an underground object exploration device for exploring underground pipes and the like buried underground. [Prior Art] Generally, when exploring buried pipes, etc.,
Underground radar systems based on the pulse radar method are used, and as shown in FIG. Move it in a direction transverse to the laying direction. At this time, it spreads from the transmitting antenna (θ
), its spread (θ
) can capture reflected waves from the buried pipe 5. Therefore, the observation time of the group of reflected waves 101 from the buried pipe 5 observed by the transmitting/receiving antenna section 6 at each moving point, that is, the electromagnetic wave propagation time t, is D'≒(L2 +D2)1/2...・
・・・・・・・・・(1) t=2D'/V・・・・・・
・・・・・・・・・・・・・・・(2) V=C/
εS1/2・・・・・・・・・・・・・・・・・・
(3) From equation (1), equation (2), and equation (3), t=2[(L2 +D2)・εS]1/2/
C......(4) 0003], and as shown in FIG. 10(b), the
It has a hyperbolic correlation with the moving distance L of the receiving antenna unit 6. Here, D is the burial depth of the buried pipe, V is the electromagnetic wave propagation speed in the buried medium, that is, underground 4, C is the speed of light, and εS
are the same permittivity. Further, the received reflected waves are displayed on the display device 13 as a ground plane image via the arithmetic unit 15, and the buried pipe reflected wave group 101 described above is captured as a hyperbolic reflected image 102 based on the reflected wave amplitude intensity. . However, since the underground is extremely non-uniform compared to the air, various miscellaneous reflected wave groups 103 are observed in addition to the buried pipe reflected wave group 101 described above. Recognizing the existence of buried pipes from among the various reflected waves observed,
In addition, as a first example for replacing the recognized electromagnetic wave propagation time t to the buried pipe with the buried depth D, Japanese Patent Application Laid-Open No. 1-280
There is a synthetic aperture method disclosed in Japanese Patent No. 275. This is done by changing the relative permittivity in predetermined steps for the group of reflected waves observed on the earth's surface to form a synthetic aperture, and then calculating the degree of integration of the amplitude intensity of the group of reflected waves at each relative permittivity. seek. At this time, the buried pipe reflected waves observed with a hyperbolic correlation have a higher degree of integration than the miscellaneous reflected waves that do not have a hyperbolic correlation, and synthetic aperture is performed using the true dielectric constant. The degree of integration is at its maximum when This method recognizes the existence of a buried pipe from these and estimates the relative permittivity of the buried medium, that is, the soil, to obtain the buried depth. However, Fig. 11 (
As shown in a), there are vertical excavation surfaces a and a' for laying buried pipes under an actual road. Furthermore, the inside of this vertically excavated surface is mainly composed of backfilling material c such as sand, and the vertically excavated surface often has electrical properties, that is, dielectric constant, that are significantly different from those of the conventional ground b. Therefore, since electromagnetic waves are reflected on surfaces with varying relative dielectric constants, in the cross-sectional survey generally performed on buried pipes 5,
), the buried pipe reflected image 102 has hyperbolic continuity only when the transmitting/receiving antenna section 6 is moving between a and a' in the vertical excavation plane on both sides of the buried pipe. There are many. When the continuity of the hyperbolic shape is short in this way, the degree of accumulation of the buried pipe reflected waves due to the synthetic aperture is the same or smaller than the miscellaneous reflected waves, so the existence of the buried pipe 5 cannot be recognized, and the hyperbolic shape The synthetic aperture method of the first example, in which shape continuity is essential, cannot be applied. Furthermore, even if a hyperbolic shape is observed, in the case of medium- or large-diameter pipes or groups of pipes with multiple threads, it is necessary to understand the pipe diameter and shape in advance and perform synthetic openings. If it is not possible to determine the burial depth accurately, it is not possible to obtain a highly accurate burial depth. A second example of the prior art is a method of recognizing the existence of a buried pipe without depending on the hyperbolic correlation of a group of reflected waves from the buried pipe as in the first example, Special request 1976
This is a frequency analysis method described in No. 2-268130. This method divides each observed reflected signal into a predetermined time period, converts the divided signals into the frequency domain to obtain the spectral distribution, and calculates the spectral peak frequency, DC component ratio, half-value width, etc. from this spectral distribution. This method calculates parameter values based on the spectral distribution. According to this method, reflected wave parameter values from buried pipes are concentrated in a specific range, so by removing reflected signals whose parameter values are outside the predetermined range as unnecessary reflected waves, Only the reflected signal from the tube can be extracted and its presence recognized. However, with this method, there is no effective way to know the dielectric constant in the buried medium, and the dielectric constant is corrected in advance using a reference tube of known buried depth, for example, near the measurement location. In addition, the synthetic aperture method of the first example and the second example
As shown in FIG. 10(a), the frequency analysis method in this example performs an investigation by moving the transmitting/receiving antenna section 6 in the transverse direction of the buried pipe 5 that is continuous in the longitudinal direction, and then detects the reflected waves. This is a way to capture it. Therefore, even if the presence of a buried pipe is recognized in the first cross-sectional survey, and then the movement line of the transmitting/receiving antenna unit 6 is moved in parallel in the longitudinal direction and the survey is performed again, the existence of the buried pipe is recognized. It has not been possible to confirm whether these are the same underground pipes, and the direction of installation can only be estimated based on road configuration, etc. [0006] Furthermore, as a third example of the prior art, as a method for estimating the relative dielectric constant in a buried medium, there is a paper published in October 1982 in the collection of papers of the Japan Society for Physical Exploration, P59-P60, ``Underground Buried Using Electromagnetic Wave Reflection Method''. ``Object Exploration'' describes a wide-angle measurement method mainly targeting strata boundary surfaces. In this method, as shown in FIG. 12(a), by using a transmitting antenna section 1 and a receiving antenna section 2 in which a transmitting antenna and a receiving antenna are arranged in respective boxes, only the receiving antenna section 2 is moved, and the main The reflected wave from the surface of change in relative permittivity with a planar spread, that is, the strata boundary surface 7, is observed. At this time, the electromagnetic wave propagation time t of the reflected wave from the strata boundary surface 7 observed by the receiving antenna section 2 at each moving point is t=(L
2 +4D2 ) 1/2 /V・・・・・・・・・・・・
...(5), t=2 [(L2 +4D2)・εS ]1/2
/C・・・・・・(6) As shown in FIG. 12(b), the receiving antenna section 2
has a parabolic correlation with the moving distance L. From this, the curve (parabola) of the reflected image 202 formed by the group of reflected waves 201 having a parabolic correlation becomes a straight line on the L2 - t2 plane, and from the slope of this straight line, the propagation velocity of the electromagnetic wave, that is, the dielectric constant can be estimated. but,
Under a road with a multilayer structure, such as a surface layer of asphalt, a roadbed made of crushed stone, or a roadbed made of conventional soil, the relative dielectric constant generally tends to be small in shallow layers and large in deep layers. . Therefore, the relative permittivity determined by the wide-angle measurement method is the average value of each layer between the ground surface and the strata boundary surface 7, and the relative permittivity between the ground surface and buried pipes is calculated to obtain a highly accurate burial depth. It doesn't matter. Therefore, if the wide-angle method is used for buried pipes that are continuous in the longitudinal direction instead of the strata boundary surface 7, accurate dielectric constants can be obtained for each pipe. However, in order to move the receiving antenna unit 2 directly above the underground pipe,
It is necessary to know the direction in which the buried pipe will be laid in advance, and this cannot be done using only the wide-angle method. [0007] The synthetic aperture method shown in the first conventional example is difficult to use when exploring a buried pipe and when there is no continuity of hyperbolic shape in the reflected image of the buried pipe. However, there was a drawback that the existence of buried pipes could not be recognized. In addition, even if the buried pipe reflection image is observed to have a hyperbolic shape, it is necessary to understand the pipe diameter and shape in advance and perform synthetic apertures.If these cannot be known in advance, it is necessary to obtain a highly accurate burial depth. The disadvantage was that it was not possible. Furthermore, the frequency analysis method shown in the second example cannot actually determine the relative permittivity of the buried medium in which the buried pipe is laid, and the relative permittivity is corrected using a known reference pipe. Therefore, there was a drawback that accurate burial depth could not be obtained. moreover,
Both the synthetic aperture method and the frequency analysis method only estimate the installation direction of the buried pipe from the road shape and the like. In addition, the third example, a method for estimating the relative permittivity in a buried medium, can obtain an accurate relative permittivity, but the receiving antenna section must be moved directly above the buried pipe in order to calculate the relative permittivity. In this case, the disadvantage is that the direction in which the buried pipe will be laid must be known in advance. Therefore, an object of the present invention is to recognize the existence of a group of reflected waves from a buried pipe even when they do not have hyperbolic continuity in a cross-sectional survey that is generally performed in an underground radar system, and to At the same time, we can calculate the relative dielectric constant of the ground surface and the electromagnetic wave propagation medium between the buried pipes, that is, the soil, regardless of the hyperbolic continuity and the diameter and shape of the buried pipes. The objective is to obtain accurate burial depth. [Means for Solving the Problems] In order to achieve the above-mentioned object, the present invention includes a transmitting antenna part having a transmitting antenna, a receiving antenna part having a receiving antenna, and a pulse signal to the transmitting antenna. A pulse generator for transmitting, a sampling device for sampling the reflected signal received by the receiving antenna, and a sampling device for converting the reflected signal into the frequency domain to calculate the spectral distribution and detecting the buried pipe based on the spectral peak frequency, DC component ratio, and half width. A waveform analysis device that recognizes the reflected signal from the underground pipe is used to gradually move only the receiving antenna section directly above the recognized buried pipe in the installation direction on the ground surface, and detect the reflected signal from the buried pipe corresponding to the moving distance of the receiving antenna. Determine the dielectric constant of the buried medium from the change in propagation time of the reflected wave,
a calculation unit that calculates the burial depth based on this relative dielectric constant;
It is equipped with an image display device. [Operation] The reflected signal from the buried pipe is converted into the frequency domain and its spectral distribution is calculated. Then, the buried pipe reflection image is recognized based on the spectral peak frequency, DC component ratio, and half-value width. The relative permittivity of the buried medium is determined from the change in the propagation time of the reflected wave corresponding to the moving distance of the receiving antenna section that moves directly above the recognized buried pipe along the installation direction, and based on this relative permittivity. The burial depth is calculated. [Embodiment] As a first means of recognizing the existence of a buried pipe and assuming the laying direction of the present invention, a frequency analysis method, which is the second example of the prior art, is used. The second method for obtaining the burial depth by determining the relative dielectric constant in the electromagnetic wave propagation medium, that is, in the soil, uses the wide-angle method, which is the third example of the prior art. The second means does not require separate devices and can be easily implemented with the same device, unlike the conventional device, which consists of the first means and the second means using separate devices. It's different from what you had. In addition, the most important feature is that it is possible to conduct cross-sectional surveys, which are generally performed on buried pipes, without relying on the hyperbolic shape of the group of reflected waves from buried pipes, without depending on the correlation. The hyperbolic correlation of the reflected wave groups from the buried pipe, which was essential in the first example of the technique, is no longer necessary. Embodiments of the present invention will be described below with reference to the drawings. FIGS. 1(a) and 1(b) are block diagrams showing an embodiment of an underground pipe exploration device according to the present invention,
FIG. 1(a) shows the first means for recognizing the existence of the buried pipe 5 and assuming the laying direction, and FIG. 1(b) shows the first means for identifying the laying direction.
and a second means for determining the dielectric constant of the buried medium between the buried pipe 5 and the ground surface, that is, the soil, and obtaining the buried depth,
These first and second means are the same device. First, the structure and operation of the first means for recognizing the existence of the buried pipe 5 and assuming the installation direction will be explained based on FIG. 1(a). A high-output impulse (monopulse) signal output from the pulse generator 10 is supplied to the transmitting antenna section 1 having broadband frequency characteristics, where the impulse signal is converted into an electromagnetic wave and sent to the underground 4. Then, the reflected waves from the buried pipe 5 existing underground 4 and other miscellaneous reflected waves are received as an observation signal, that is, a reflected signal, by the receiving antenna section 2 having broadband frequency characteristics, and the received observation signal is The sample is sampled by a sampling device 11. Next, the transmitting/receiving antenna parts 1 and 2 connected by the jig 3 and arranged at right angles to the buried pipe 5 are moved in a direction transverse to the buried pipe 5,
Repeat sampling at predetermined intervals. The sampled observation signal is supplied to the waveform analyzer 12, which extracts only the reflected signal from the buried pipe 5, which is the target object, and displays only the reflected signal from the buried pipe 5 on the display device 13. The transmitting/receiving antenna unit 1 connected by these series of operations
, 2 is displayed, and since only the reflected signal of the buried pipe 5 is displayed, its presence can be easily recognized, and the point directly above the buried pipe 5 on the ground surface can be identified. . Next, specifying the installation direction shown in FIG. 1(b),
and the operation of the second means for obtaining the burial depth will be explained. The transmitting/receiving antenna parts 1 and 2 are arranged directly above the buried pipe 5 and parallel to the laying direction, and separated by a jig 3. Next, the operation is similar to that described in the first means, that is, the electromagnetic waves sent out from the transmitting antenna section 1 are received by the receiving antenna section 2 as reflected waves from underground 4 or buried pipes 5, and sampled by the sampling device 11. Next, by the method described later, only the receiving antenna section 2 is moved directly above the buried pipe 5, sampling of reflected waves is repeated at predetermined intervals, and the sampled observation signal is supplied to the waveform analyzer 12, Only the reflected signal from the is extracted and displayed on the display device 13. Next, the calculation unit 14 examines the change in the propagation time of the reflected wave from the buried pipe corresponding to the moving distance of the receiving antenna unit 2, and calculates the relative permittivity of the ground surface and the buried medium between the buried pipe, that is, the soil. , based on which the burial depth is calculated. Next, the operation of the waveform analysis device 12 will be explained. The waveform analysis device 12 first divides the reflected signal sampled and supplied by the sampling device 11 into predetermined time intervals. That is, since the reflected signal from the underground 4 is a mixture of various miscellaneous reflected signals in addition to the reflected signal from the buried pipe 5 at different time positions, these various reflected signals are individually divided. do. This division method includes a constant time division method that divides by a constant time width ΔT, a zero
There is a zero-cross division method in which the signal is divided by a time equivalent to one cycle using a cross method, but in this embodiment, an example in which division is performed by the zero-cross method will be explained. FIG. 2 is an example of waveform division of the reflected signal 21 supplied to the waveform analyzer 12 using the zero-crossing method. The section indicated by the arrow in FIG. 2 is a time interval equivalent to one cycle according to the zero-crossing method, and a waveform number is assigned to each divided waveform. Here, an example in which waveform No. 1 is divided is shown in the upper part of FIG. The divided waveform 21' is processed by the waveform analysis device 12.
In the step, the signal is transformed into the frequency domain by fast Fourier transform processing, and the spectral distribution is determined. That is, the spectrum with the maximum intensity (peak) is detected from the spectral distribution shown in the lower part of FIG. 3, and the spectrum peak frequency fp, the spectrum intensity Ip with respect to the spectrum peak frequency fp,
Read the DC component intensity Idc and the half width W. Further, the DC component ratio Rdc is calculated from the DC component intensity Idc and the spectral intensity Ip using the following equation. Rdc=Idc/Ip・・・・・・・・・・・・・
...(7) Perform the above process for all the divided waveforms of the observed signal, and use the characteristics of Figures 4 and 5 to obtain fp1<fp<fp2, W1<W<W2, Rdc1
Divided waveforms having values other than <Rdc<Rdc2 are removed as unnecessary reflected waves. Here, FIGS. 4 and 5 show fp-R of various divided waveforms derived from observation signals obtained through numerous experiments.
It is a graph showing dc, fp-W distribution. In the figure, black circles indicate the characteristics of reflected waves from the buried pipe 5, and white circles indicate characteristics of unnecessary reflected waves. The reflected wave from the buried pipe 5 clearly falls within a certain range, that is, fp1<f
p<fp2, W1<W<W2, Rdc1<Rdc<Rd
It can be seen that the distribution is concentrated in the c2 range. fp
1, fp2, W1, W2, Rdc1, Rdc2 value 1
Examples are shown in Table 1. [Table 1] Note that there are divided waveforms that satisfy any of the filtering conditions of spectral peak frequency fp, half width W, and DC component ratio Rdc, but as shown in Table 2, There is only one divided waveform (ie, waveform No. 4) in the observed signal that satisfies the three conditions at the same time, and this divided waveform is considered to be the reflected waveform of the buried pipe 5, and only this divided waveform is extracted. Here, Table 2 shows the values of the spectral peak frequency fp, half-width W, and DC component ratio Rdc calculated for each divided waveform shown in FIG. 2. [Table 2] [0020] When the waveform analysis processing described above is applied to the observed signal in FIG. 2, unnecessary reflected signals are removed and only the waveform of the reflected signal from the buried pipe 5 becomes visible, as shown in FIG. can get. Also, since FIG. 6 is a waveform corresponding to A-A in FIG. 7, if these effects are applied to all observation signals sampled at predetermined intervals as the antenna moves, the result will be as shown in FIG. , only the reflected image of the buried pipe based on the amplitude strength of the reflected wave is displayed in the ground cross-sectional diagram constructed in a coordinate system in which the horizontal axis is the antenna movement distance and the vertical axis is the electromagnetic wave propagation time. FIG. 8 shows a perspective view of this embodiment. Figure 8 (a
) are the transmitting/receiving antenna sections 1 of each of the first and second means.
, 2 and the buried pipe 5, FIG. 8(b) shows the respective ground plane images 301, 302 and the buried pipe reflection image 102,
It is 202. In the first means for recognizing the existence of the buried pipe 5 and assuming the installation direction, the transmitting antenna part 1 and the receiving antenna part 2 are connected using the jig 3, and the buried pipe estimated from the road shape etc. transverse to the laying direction,
That is, the transmitting/receiving antenna sections 1 and 2 are moved in the direction from A to C, and the reflected signal from the buried pipe 5 is captured. From the various reflected signals observed, only the reflected signal from the buried pipe 5 is extracted by the waveform analyzer 12, and as shown in FIG. 8(b), A
→ Only the reflected image 102 of the buried pipe 5 is displayed in the ground plane image 301 corresponding to the moving distance of the transmitting/receiving antenna sections 1 and 2 in the C direction. With this operation, the existence of the buried pipe 5 can be easily recognized, and the point directly above it, that is, the point B, can be specified. Next, the antenna scanning line is changed and the above operation is performed again from A' to C' to specify point B'. The two points identified here, namely B → B', are the buried pipe laying direction,
At this stage, it is not known whether the two specified points are the same buried pipe or not, so the installation direction is assumed. Next, in the second means for specifying the installation direction and obtaining the burial depth, the transmitting/receiving antenna parts 1 and 2 are separated by a jig 3, and only the receiving antenna part 2 is placed directly above the buried pipe 5 in the laying direction. It is assumed to be moved in the direction B→B', and the reflected signal from the buried pipe etc. is captured. The various reflected signals observed are the first
Similar to the method described above, only the reflected signal from the buried pipe 5 is extracted by the waveform analyzer 12, and as shown in FIG. 8(b),
Only the buried pipe reflected image 202 is displayed from among the ground plane images 302 corresponding to the moving distance of the receiving antenna section 2 in the direction B→B'. FIG. 9 is a diagram explaining the second means in detail, and FIG. 9(a) is a diagram showing the relationship between the transmitting/receiving antenna sections 1 and 2 and the buried pipe 5, and FIG. 9(b) is a graph (theoretical parabola 401, etc.) for estimating a buried tube reflection image 202 and relative dielectric constant as the receiving antenna section 2 moves. If the two points assumed by the first means, that is, points B and B' are the same buried pipe, the receiving antenna section 2 is moving directly above the buried pipe 5, and as shown in FIG. 9(a), The electromagnetic wave propagation time t1 of the reflected wave from the buried pipe 5 observed by the receiving antenna section 2 at each moving point is t0 = 2 [[, where W is the initial distance between the transmitting antenna section 1 and the receiving antenna section 2. (W/2)2 +D2]・εS
]1/2 /C・・・・・・・(8) t1 = 2
{[[(W+L)/2]2 +D2]・εS }1/
2 /C...(9) From equations (8) and (9), t1 = [(L2 +2WL)・εS +t02・
C2]1/2/C... (10) As shown in Figure 9(b), the electromagnetic wave propagation time t
1 and the moving distance L of the receiving antenna section 2 have a parabolic correlation. That is, if there is continuity in the parabolic correlation, it can be confirmed that the points B→B' are the same buried pipe, and the installation direction of the buried pipe 5 can be identified here. Next, at the stage of determining the relative dielectric constant in the electromagnetic wave propagation medium, that is, in the soil 4, and obtaining the burial depth, as shown in FIG.
), the buried pipe reflection image 202 formed by the group of buried pipe reflection waves 201 observed in a parabolic shape is expressed by the formula (
10), the electromagnetic wave propagation time changes due to the difference in relative dielectric constant, and its slope changes. Therefore, by evaluating this slope, the relative dielectric constant can be found. Therefore, as an example of a method for evaluating this slope and estimating the relative permittivity, in addition to the method of estimating the relative permittivity from the slope of a straight line on the L2 - t2 plane as described above, Possible methods include a method of performing a synthetic aperture on a group of waves, a method of calculating from the time position of a group of reflected waves and a moving distance of the receiving antenna section 2 using the Pythagorean theorem, etc.; The method of superposition of theoretical parabolas will be explained below as the easiest method for estimating from . As shown in FIG. 9(b), the display device 13
Then, the parabolic reflection image 202 obtained by measurement and the theoretical parabola according to equation (10) with the assumed dielectric constant are displayed. In other words, the reflected wave time position T0 when L=0m
The electromagnetic wave propagation time t0 is read by specifying the coordinate of -p using a cursor key or the like, and a theoretical parabola 401 is displayed on the display device 13 according to formula (10) based on the preset general dielectric constant of soil. Next, calculate the dielectric constant εs in equation (10) to the first decimal place using the cursor keys, etc.
The angle of the theoretical parabola 401 is shifted by approximately 0.5 to change the slope of the theoretical parabola 401, and the theoretical parabola is superimposed on the reflected image 202. In this case, the theoretical parabola 402 when they completely overlap
The relative permittivity that forms this is the true relative permittivity. At this time, while changing the dielectric constant, D=C・t0
The burial depth is also displayed by /(2·εs)1/2. Through these operations, the dielectric constant can be determined from the reflected image 202 from the buried pipe 5 obtained in a parabolic shape, and highly accurate buried depth data can be obtained. These are cross-sectional surveys in the A→C direction, and as shown in FIG. In the B→B' direction, the antenna part does not cross the vertical excavation surface and operates within the same burial depth (backfilling material), so parabolic reflection images can be observed efficiently.
Since the parabolic shape is not affected by the diameter of the buried pipe 5, etc., it is possible to obtain a highly accurate dielectric constant, that is, a buried depth. Note that this underground object exploration device can be applied not only to the exploration of underground objects, but also to the exploration of invisible objects such as reinforcing bars in concrete. [0025] As explained above, by using the device of the present invention, the hyperbolic correlation between the moving distance of the transmitting/receiving antenna section and the electromagnetic wave propagation time when a buried pipe is surveyed in the transverse direction can be realized. The existence of buried pipes can be recognized completely regardless of the Also,
At the stage of identifying the installation direction and determining the dielectric constant in the buried medium, the receiving antenna is moved in the direction of the buried pipe installation, so there is no influence from vertical excavation surfaces, and it is not affected by the diameter of the buried pipe. , it is possible to obtain a group of parabolic reflected waves sufficient to estimate the relative dielectric constant, and it is possible to obtain a highly accurate burial depth.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of an underground object exploration device of the present invention.

FIG. 2 is a waveform diagram of an observation signal whose waveform is analyzed.

FIG. 3 is a diagram showing a divided waveform diagram of an observation signal and its spectral distribution.

FIG. 4 is a graph showing the relationship between the DC component ratio of the divided waveform and the spectral peak frequency.

FIG. 5 is a graph showing the relationship between the half-width of a divided waveform and the spectral peak frequency.

FIG. 6 is a waveform diagram of a reflected signal from which unnecessary reflected signals have been removed.

FIG. 7 is a cross-sectional view of a buried pipe corresponding to a reflected signal waveform.

FIG. 8 is a perspective view of the apparatus of the embodiment.

FIG. 9 is an explanatory diagram illustrating the exploration method of the apparatus of the embodiment.

FIG. 10 is an explanatory diagram illustrating a conventional underground object exploration method.

FIG. 11 is an explanatory diagram illustrating problems in the conventional buried object exploration method.

FIG. 12 is an explanatory diagram illustrating a conventional underground object exploration method.

[Explanation of symbols] 1 Transmission antenna section 2 Receiving antenna section 3 Jig 4 Underground 10 Pulse generator 11 Sampling device 12 Waveform analysis device 13 Image display device 14 Calculation section

Claims (1)

[Claims] Claim 1: A transmitting antenna section including a transmitting antenna, a receiving antenna section including a receiving antenna, a pulse generator for transmitting a pulse signal to the transmitting antenna, and a sampling device for sampling a reflected signal received by the receiving antenna. and a waveform analyzer that converts the reflected signal into the frequency domain to calculate the spectral distribution and recognizes the reflected signal from the buried pipe based on the spectral peak frequency, DC component ratio, and half-width. Gradually move only the receiving antenna part directly above the buried pipe in the installation direction, and find the relative dielectric constant of the buried medium from the change in propagation time of the reflected wave from the buried pipe corresponding to the moving distance of the receiving antenna. An underground object exploration device comprising: a calculation unit that calculates a burial depth based on a relative dielectric constant; and an image display device.