JP3309242B2 - Underground dielectric constant measuring method, geological measuring method and position measuring method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of measuring the relative permittivity of an underground by transmitting an electromagnetic wave into the ground and receiving the reflected wave, and measuring the geology using the measured relative permittivity. And a method for measuring the position of an obstacle or the like underground using the measured relative dielectric constant.

[0002]

2. Description of the Related Art Conventionally, in order to perform an underground exploration in front of a face in a shield method, a method of measuring a relative permittivity in the ground and a distance to a reflector has been disclosed in, for example, JP-A-5-529.
There is a method described in JP-A-49-49. This method, apart transmitting antennas and the receiving antenna by a distance X1 place, this distance X1, obtaining from the received surface propagation wave propagation time t ₁ Tokyo a relative dielectric constant εr of the following equation (2). εr = {(t ₁ × c) / X1} ² (2) where c is the speed of light. The velocity ν of the electromagnetic wave is ν
= Order given by c / √εr, and its speed, the propagation from the time t ₂ Metropolitan at the peak point of the received reflected waves to determine the distance X2 to the reflector by the following equation (3). _{X2 = ν · t 2/2} ····· (3)

However, this has the following problems. Since this method assumes that the transmitting antenna and the receiving antenna are separated from each other, the transmitting antenna and the receiving antenna are necessarily arranged at a predetermined angle, and the geometrical error is reduced. It greatly affects measurement accuracy. Since electromagnetic waves pass through places where they can easily propagate,
The angle between the transmitting antenna and the receiving antenna causes a non-linear element in the propagation / reflection path of the electromagnetic wave, which causes a decrease in measurement accuracy. When applied to the shield method, a separate type electromagnetic wave radar antenna in which the transmission antenna and the reception antenna are separated is used, and the transmission antenna and the reception antenna are attached separately to the cutter face plate of the shield machine. , Due to its structure, mounting space is limited,
The size of the radar antenna also differs depending on the selected frequency. For this reason, in order to mount a radar antenna having a predetermined frequency capable of performing sufficient exploration, it is necessary to remodel the cutter face plate, which increases the cost and the construction period. On the other hand, if the cutter faceplate cannot be modified, the usable frequency of the radar antenna is limited, and satisfactory search cannot be performed.

[0004] As a method of measuring the geology (soil quality) during shield excavation, there is a method disclosed in Japanese Patent Publication No. 5-25994. According to this method, earth and sand is collected from a chamber of a shield machine and the particle size is measured by a particle size measuring device, and the soil quality is determined from the measured particle size.

[0005] However, since this is a soil determination using only the average particle size of the earth and sand taken into the chamber as a parameter, when the excavated soil is mixed with muddy water or muddy material, it is affected by this and the shield excavation is performed. If the ground around the front of the machine is composed of different geological features, the geology cannot be distinguished from each other, and it is difficult to say that the result indicates the geology around the front of the shield machine.

[0006]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a method for measuring the relative permittivity in the ground which does not have the above-mentioned problems and which can measure the relative permittivity in the ground accurately, and a method for measuring the relative permittivity in the ground. It is an object of the present invention to provide a geological measurement method capable of clearly measuring the surrounding geology and a position measuring method capable of accurately measuring a distance to a reflection object or the like.

[0007]

In the relative dielectric constant measuring method according to the present invention, an electromagnetic wave having a constant frequency f0 is transmitted from the transmitting antenna into the ground, and the reflected wave is received by the receiving antenna, and the attenuation period of the first period is determined. Is compared with frequency / relative permittivity characteristic data indicating a correlation between the frequency and the relative permittivity obtained in advance to obtain a corresponding relative permittivity.

FIG. 5 is a graph of the frequency / relative permittivity characteristic data. If the frequency f is plotted on the horizontal axis and the relative permittivity εγ is plotted on the vertical axis, the value of the relative permittivity εγ with respect to the change in the frequency f becomes Draw an exponential curve. This can be expressed by the following relational expression (4), and the relative frequency εγ can be obtained by applying the discriminated frequency f to the relational expression (4). εγ = a × b ^{1 / f} (4) where a is a first relative permittivity regression coefficient and b is a second relative permittivity regression coefficient.

The transmitting antenna and the receiving antenna transmit and receive electromagnetic waves by an electromagnetic radar integrated without separating from each other as in the related art.

In the geological measurement method according to the present invention, an attenuation rate is obtained from a natural attenuation waveform when there is no obstacle reflection or the like, and a specific resistance or a reciprocal conductivity is calculated from the attenuation rate. The resistance or conductivity and the relative permittivity measured as described above are compared with each parameter value of a database that is pre-constructed by geological classification using the conductivity or the specific resistance and the relative permittivity as parameters, and this database is used. Extract the relevant geology from the inside.

Further, in the position measuring method according to the present invention, a voltage peak point of a cross-correlation function between a received target signal waveform and a natural attenuation waveform when there is no obstacle reflection or the like is obtained, and a time T of the peak point is obtained. The position of the reflection target or the like is calculated from the propagation speed ν of the electromagnetic wave obtained from the relative dielectric constant measured as described above.

[0012]

When the frequency shifts when an electromagnetic wave of a certain modulation frequency f0 propagates through a substance, the shift amount Δf is determined by the relative permittivity of the substance. When an electromagnetic wave penetrates into substances having different relative dielectric constants, the electromagnetic wave is reflected at a boundary surface between the two substances. When electromagnetic waves are generated periodically as in electromagnetic wave exploration, they are repeatedly reflected from the boundary surface,
The reflected signal has a frequency characteristic determined by the relative permittivity of the substance that has permeated, and Δf
The frequency is shifted. This means that an electromagnetic wave having a frequency f0 and a signal intensity V1 transmitted from the transmitting antenna and a signal intensity V2 having a frequency shift Δf with respect to the electromagnetic wave.
Means that the signals are combined and detected by the receiving antenna.

Therefore, in the present invention, the relative permittivity is obtained by using the frequency of the first period of the surface reflected wave that combines and interferes with the transmitted wave and the reflected wave propagating in the ground. If the transmission frequency f0 is constant, the frequency shift amount Δf
The relationship between the change in the relative permittivity and the value of the relative permittivity is determined as described above, so the relationship between the change in the frequency f of the frequency-shifted received signal and the value of the relative permittivity is also determined, as shown in FIG. The value of the relative permittivity εγ with respect to the change of f draws an exponential curve.

Therefore, if the frequency f of the attenuation cycle of the first cycle of the surface reflected wave is applied to this exponential curve,
It is possible to know the relative permittivity εγ underground where the transmission frequency f0 is shifted to the frequency f.

The characteristic graph of FIG. 5 can be expressed by the above-mentioned relational expression (4).
The relative permittivity regression coefficient a and the second relative permittivity regression coefficient b can be obtained as follows. The relational expression (4) is replaced by Ln · εγ = Ln (a × b ^{1 / f} ) = Ln · a + (1 / f) Ln · b, and y = α + βx (where y = Ln · εγ, x
= 1 / f, α = Ln · a, β = Ln · b), and the relative permittivity regression coefficients a and b are obtained by f and εγ by linear regression.

On the other hand, when the received signal of the receiving antenna has a naturally attenuated waveform, it indicates that there is no reflector such as an obstacle in the ground. That is, the natural attenuation waveform can be regarded as a reflection signal from the ground surface affected only by the relative dielectric constant in the ground where there is no specific reflector. On the other hand, the reflected signal when there is an obstacle in the ground is affected by the relative permittivity of the ground and the relative permittivity of the obstacle. Therefore, when the natural attenuation waveform is used as a temporary reference waveform and cross-correlation processing is performed with a reflection signal including reflection from an obstacle,
Only the propagation time difference between the ground surface and the obstacle can be extracted. Then, the propagation speed ν (ν = c / c) of the electromagnetic wave obtained from the propagation time difference T and the relative dielectric constant εγ measured earlier.
√εγ) and an obstacle L, for example, can be calculated from the following equation (5). L = ν × T (5)

The attenuation rate α can be obtained by analyzing the natural attenuation waveform in a known manner.
The attenuation characteristic of the natural attenuation waveform differs depending on the geology as the propagation medium, and the attenuation rate α and the specific resistance ρ (conductivity σ) of the medium (geology)
, That is, ρ = 1 / σ), the following equation (6) holds. α = (60π / ρ) × √εr (6) where π is a circular constant.

(A), (B) and (C) of FIG. 11 show changes in the natural attenuation waveform due to the difference in the specific resistance ρ of the geology. In this figure, reference numeral 5 denotes an electromagnetic wave radar. FIG. 12 is a graph showing a change in the damping characteristic due to a change in the specific resistance ρ. As can be seen from this figure, when the specific resistance ρ is large (the conductivity σ is small), the attenuation rate α is small, and when the specific resistance ρ is small (the conductivity σ is large), the attenuation rate α is large. Therefore, the specific resistance ρ is obtained from the attenuation rate α, and the specific resistance ρ
Can be used to estimate the type of geology. However, in such a geological determination using only the specific resistance ρ as a parameter,
Because it is based on the attenuation characteristic of the natural attenuation waveform,
Easy to cause errors. Therefore, in the present invention, since the relative permittivity also differs depending on the geology, the relative permittivity obtained as described above as a parameter in addition to the specific resistance ρ (or the reciprocal conductivity σ) is used as a parameter. The accuracy is improved by determining the type.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the present invention is applied to a shield method will be described below in detail with reference to the drawings.

As shown in FIG. 1, an electromagnetic radar 5 in which a transmitting antenna 3 and a receiving antenna 4 are integrated is stored in a radar protection box 6 at one position on the front surface of a cutter face plate 2 of a shield machine 1. Embedded and transmitting antenna 3
When the electromagnetic wave 8 is reflected from the ground toward the ground 7, the reflected wave from the ground is received by the receiving antenna 4 at the same point as the transmitting antenna 3. The front surface of the radar protection box 6 is closed by a front protection plate 6a.

FIG. 2 shows a system configuration for implementing the method according to the present invention. The system includes a transmission / reception processing circuit 9 for controlling transmission / reception of the electromagnetic wave radar 5, an A / D converter 10 for converting a reception analog signal received by the reception antenna 3 and input through the transmission / reception processing circuit 9 into a digital signal, CPU and DSP (Digital Signal Processor)
11, a computer including a memory (ROM, RAM, disk storage medium, etc.), a transmission signal output unit 12 for transmitting a transmission signal to a transmission / reception processing circuit 9 in accordance with instructions from the computer 11, and a display output device 13 such as a CRT or a printer. Have been.

In the present embodiment, the relative permittivity in the ground is measured by this system, then the distance to the obstacle is measured, and the type of the geology is also measured. First, the method of measuring the relative permittivity will be described. I do.

As shown in FIG. 1, when an electromagnetic wave 8 is transmitted from the transmitting antenna 3 as a search signal, a reflected wave from the ground is received by the receiving antenna 4, and the reflected wave is roughly divided into the ground surface. A reflected wave 15A from the inside 14 and a reflected wave 15B from the inside penetrating into the underground 7 are shown. The reflected wave 15A from the ground surface 14 is equivalent to the fundamental frequency component of the transmitted electromagnetic wave 8, whereas the reflected wave 15B from the underground is affected by the relative permittivity εγ in the ground. The received signal waveform at the transmission / reception processing circuit 9 changes as shown in FIG.
15B becomes a combined attenuation waveform, which is generally called a surface reflected wave. However, in the figure, the surface wave region 16 is an attenuation signal of the first cycle.

The received surface wave is obtained by changing the electromagnetic wave 8 penetrating into the underground 7 according to the relative dielectric constant εγ of the underground 7 as described above, and as shown in FIG. If the relative dielectric constant of the underground 7 is, for example, εγ1, the frequency f1 (peak point is time t1) in the exploration signal time domain, and if the relative dielectric constant of the underground 7 is εγ2, the frequency f2 is in the exploration signal time domain.
(The peak point is time t2). When such a relationship between the relative permittivity and the frequency is represented by a characteristic graph, an exponential curve as shown in FIG. 5 is obtained, which can be expressed by the relational expression (4) as described above.

Therefore, in this embodiment, the relational expression (4)
Is stored in the computer 11 in advance, the received analog signal is converted into a digital signal by the A / D converter 10, and the frequency f is discriminated from the attenuation cycle of the first cycle. Then, the relative dielectric constant εγ corresponding to the frequency f is obtained by performing an evaluation or a comparison process according to the relational expression (4). The obtained relative dielectric constant εγ is stored in a memory as a parameter for distance measurement. Also, if necessary, the display output device 1
3 can be displayed on a display screen or printed out.

Next, an example of measuring the distance to an obstacle existing in the ground 7 by the position measuring method according to the present invention will be described.

The present invention utilizes a cross-correlation method as a signal analysis method. First, a brief description will be given of this method. A reference signal x (t) is compared with a target signal y (t) to be compared with a time difference k therefrom. The cross-correlation function of the following equation (7) or (8)
It can be represented by an equation.

[0028]

(Equation 1)

[0029]

(Equation 2)

Therefore, in the present embodiment, as shown in FIG. 6, a waveform of the reference signal which is close to the natural attenuation waveform is set, and the reference signal is compared with the target signal actually received by the receiving antenna 4. The correlation function is calculated by the computer 11. 7 is a reception waveform when there is no obstacle, and FIG. 8 is a reception waveform when there is an obstacle. When the cross-correlation processing is performed with the reference waveform of FIG. FIG. 9 shows the cross-correlation waveform when an obstacle is present, as shown in FIG. In the example of the figure, the cross-correlation waveforms when there is no obstacle are correlation peaks P1 and P2 having large absolute values.
After the occurrence of the correlation peak P3 having a small absolute value, the correlation peak does not occur, whereas the cross-correlation waveform when there is an obstacle shows the correlation peaks P4 and P5 even after P3.
-P7 and P8 have appeared.

Therefore, in the present embodiment, the correlation peaks P1, P2, and P3 that occur even when there is no obstacle are excluded, and P3
Correlation peaks P4, P5, P7, P8 later in time than
Is the correlation peak whose absolute value is the largest (P7 in the figure)
Is extracted, and the distance L to the obstacle is obtained from the time T at that time and the relative dielectric constant εγ obtained earlier from the following equation (9). Then, the shield machine 1 is dug while repeating such processing in real time.

L = (c / √εγ) × T (9) where c is the speed of light.

Finally, an example in which the type of geology is measured by the geological measurement method according to the present invention will be described.

A natural attenuation waveform is extracted from the received signal received as described above, and analyzed by a well-known transient phenomena analysis method to obtain an attenuation rate α, and the above-mentioned (6) is obtained from the attenuation rate α.
Ρ (or conductivity σ) is calculated according to the following equation. On the other hand, since the relative dielectric constant εγ has already been determined as described above, the type of the geology can be specified from both the relative dielectric constant εγ and the specific resistance ρ (or the electrical conductivity σ).

In specifying this, in this embodiment,
A database in which geology is distinguished by using the relative permittivity and the specific resistance (or conductivity) as parameters is constructed in advance. FIG.
3 shows this as a tabular model (in the form of table data in the computer 11), and when both the relative permittivity εγ and the specific resistance ρ (or the electrical conductivity σ) are given as a logic matrix, one corresponding Geological type is extracted.
FIG. 14 is a conceptual diagram of an extraction method using the logical matrix. Assuming an XY coordinate system in which specific resistance ρ (or conductivity σ) is taken in the X-axis direction and relative dielectric constant εγ is taken in the Y-axis direction, Is given, and the relative permittivity εγ is given as the Y value, and a geological type in which both coincide or approximate is extracted.

FIG. 15 shows the overall flow of the above processing. First, in step S1, various initial data are input from a database as initial settings, and a search signal (natural attenuation waveform) at the start of the search is input as reference data, and the initial relative permittivity (propagation speed) and geology are primarily measured. I do. In the next step S2, the received signal is subjected to A / D conversion and the reference data is subjected to logical judgment and cross correlation judgment processing.
If it is determined that the waveform is a natural attenuation waveform, the relative permittivity is measured based on the surface wave component in step S3, and the propagation velocity is also calculated. Then, in the next step S4, the attenuation factor is calculated for the natural attenuation waveform, and the specific resistance (or conductivity) obtained therefrom and the relative dielectric constant obtained in step S3 are used as parameters from the database as described above. Extract the geological type.

On the other hand, when it is determined that the waveform is a reflection waveform from the obstacle, the position (distance) of the obstacle is calculated and measured in step S5 as described above. Then, after the step S5 or S4, the measurement result is displayed and output in step S6, the data is updated, and if the mode is the repetitive search mode, the process returns to step S2 to repeat the same process for the next search signal.

It should be noted that the present invention is not limited to measurement from inside a tunnel as in the shield method, but is applicable to measurement from the ground surface.

[0039]

According to the relative dielectric constant measuring method of the present invention, the following effects can be obtained. Since the relative permittivity is determined by capturing the change in the frequency of the surface reflected wave that combines and interferes with the transmitted wave and the reflected wave propagating in the ground, the relative permittivity can be accurately measured. Since the transmitting and receiving antennas are transmitted and received by an integrated electromagnetic radar, unlike the conventional example where the transmitting and receiving antennas are separated from each other, the arrangement does not cause a decrease in measurement accuracy and is applicable to the shield method. In this case, the cutter face plate does not need to be significantly remodeled unlike the conventional example, so that the cost can be reduced and the size can be reduced.

According to the geological measurement method of the present invention, an attenuation rate is obtained from a natural attenuation waveform when there is no obstacle reflection or the like, and a specific resistance or a reciprocal conductivity is calculated from the attenuation rate. Since the corresponding geological type is extracted from the database using the obtained specific resistance or conductivity and the specific permittivity as parameters, accurate geological discrimination can be performed.

Further, according to the position measurement method of the present invention, the voltage peak point of the cross-correlation function between the received target signal waveform and the natural attenuation waveform when there is no obstacle reflection or the like is determined, and the time of the peak point is determined. Since the position of the reflection target or the like is calculated from the propagation speed of the electromagnetic wave obtained from the relative dielectric constant measured as described above, highly accurate measurement can be performed.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of an embodiment in which the present invention is applied to a shield method.

FIG. 2 is a block diagram of a system for implementing the method of the present invention.

FIG. 3 is a waveform diagram showing attenuation of a reflected wave with respect to a transmission wave.

FIG. 4 is a waveform diagram showing that the frequency of a reflected wave shifts due to a difference in the relative dielectric constant underground.

FIG. 5 is a characteristic graph showing a relationship between relative dielectric constant and frequency.

FIG. 6 is a waveform diagram of a reference signal for cross-correlation.

FIG. 7 is a reception waveform chart when there is no obstacle.

FIG. 8 is a reception waveform chart when there is an obstacle.

FIG. 9 is a cross-correlation waveform diagram when there is no obstacle.

FIG. 10 is a cross-correlation waveform diagram when there is an obstacle.

FIG. 11 is a diagram showing that the attenuation characteristic of a natural attenuation waveform changes due to a difference in specific resistance due to a difference in geology.

FIG. 12 is a characteristic graph showing a relationship between an attenuation rate and a specific resistance.

FIG. 13 is a diagram showing, as a table model, a database in which geology is distinguished by using relative permittivity and conductivity as parameters.

FIG. 14 is a conceptual diagram illustrating a method of extracting a corresponding geological type from the database of FIG.

FIG. 15 is a flowchart showing an extraction process of the embodiment.

[Explanation of symbols]

 Reference Signs List 1 shield excavator 2 cutter face plate 3 transmitting antenna 4 receiving antenna 5 electromagnetic wave radar 6 radar protection box 7 ground 8 electromagnetic wave 9 transmission / reception processing circuit 10 A / D converter 11 computer 12 transmission signal output unit 13 display output device 14 ground surface 15A Reflected wave from ground surface 15B Reflected wave from inside penetrating into the ground 16 Surface wave region

Continuation of the front page (72) Inventor Masahiro Fujiwara 1-4-4 Sumiyoshi Uozumi-cho, Akashi-shi, Hyogo Prefecture Kos Co., Ltd. (56) References JP-A-56-124039 (JP, A) JP-A-2-8754 ( JP, A) JP-A 4-131792 (JP, U) JP-B-5-25994 (JP, B2) (58) Fields investigated (Int. Cl. ⁷ , DB name) G01N 22/00-22/04 G01V 3/00-3/40 G01S 13/00-13/95

Claims (5)

(57) [Claims] An electromagnetic wave having a constant frequency f0 is transmitted from a transmitting antenna into the ground, and a reflected wave thereof is received by a receiving antenna to discriminate a frequency f from an attenuation cycle of a first cycle. A relative permittivity corresponding to a relative permittivity obtained by comparing with frequency / relative permittivity characteristic data indicating a correlation with a relative permittivity obtained in advance from a change in a shift amount Δf with respect to the ground. Method. 2. An electromagnetic wave having a constant frequency f0 is transmitted from a transmitting antenna into the ground, a reflected wave thereof is received by a receiving antenna, and a frequency f is discriminated from an attenuation cycle of a first cycle. A method of measuring the relative permittivity underground, wherein the relative permittivity εγ is obtained by applying the equation (1). εγ = a × b ^{1 / f} (1) where a is a first relative permittivity regression coefficient and b is a second relative permittivity regression coefficient. 3. The transmission / reception using an electromagnetic wave radar in which a transmission antenna and a reception antenna are integrated.
Or the method of measuring a relative dielectric constant in the ground according to 2 above. 4. An attenuation rate is obtained from a natural attenuation waveform when there is no obstacle reflection or the like, and a specific resistance or a reciprocal conductivity is calculated from the attenuation rate, and the calculated specific resistance or conductivity is calculated. Or, the relative permittivity measured by the method of 2 or 3 is compared with each parameter value of a database constructed in advance by geological classification using the conductivity or the specific resistance and the relative permittivity as parameters, and from this database A geological measurement method characterized by extracting a relevant geology. 5. A voltage peak point of a cross-correlation function between a received target signal waveform and a natural attenuation waveform when there is no obstacle reflection or the like, and a time T of the peak point and a time T of the peak point are obtained. A method for measuring the position of an underground object based on a propagation velocity ν of an electromagnetic wave obtained from a relative dielectric constant measured by a method.