JP2001194349A - Apparatus and method for inspecting back face of lining - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reliably and easily inspect the back face of a lining. SOLUTION: The value of the transfer function which is the ratio of the first physical quantity to the second physical quantity to be received by a first geophone 6 and a second geophone 7 is calculated by using the first geophone 6 to be joined with the surface side of a lining layer 2 which is a surface side layer of a laminar structure, the second geophone 7 joined with its surface side, and an exciter 5 to give the vibration of low frequency less easily influenced by the physical properties of the lining layer 2 to the lining layer 2. The first physical quantity and the second physical quantity are expressed in terms of the function of the low frequency ω, and in particular, the phase velocity CR is obtained, and a flaw in a back face layer can be clearly detected from the comparison with the reference value.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for inspecting the back of a lining body and a method for inspecting the back of the lining. The present invention relates to a back surface inspection apparatus and a back surface inspection method for a lining body for inspecting a state.

[0002]

2. Description of the Related Art Embankments and tunnels are structures having a relatively soft and brittle ground as a base layer. Such a structure is lining treated with a reinforcing material such as concrete. Poor joints may occur between the ground layer and the concrete lining layer at the ceiling. Such poor bonding,
Furthermore, back surface defects may occur due to aging. When a back surface defect occurs, there is a possibility that a part of the structure may collapse due to the bias.

In general, various non-destructive inspection methods are known for detecting the presence of a defect inside a solid structure. As such a nondestructive inspection method, a diagnostic method using ultrasonic waves and electromagnetic waves is known. It is difficult to detect a back surface defect of a concrete lining structure such as a tunnel by such a diagnostic method, and after all, it is said that a percussion by an expert is most appropriate. There is no known inspection method that is more reliable than the expert.

[0004] There is an urgent need to establish a more reliable inspection method for layered structures. Furthermore, it is particularly desirable that the inspection method be simple.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to provide an apparatus and a method for inspecting a back surface of a lining body with higher reliability. Another object of the present invention is to provide a backside inspection apparatus and a backside inspection method for a lining body having higher reliability and a simpler inspection method.

[0006]

Means for solving the problem are described as follows. The technical items appearing in the expression are appended with numbers, symbols, and the like in parentheses (). The numbers, symbols, and the like are technical items that constitute at least one embodiment or a plurality of the embodiments of the present invention, in particular, the embodiments or the examples. Corresponds to the reference numerals, reference symbols, and the like assigned to the technical matters expressed in the drawings corresponding to the above. Such reference numbers and reference symbols clarify the correspondence and bridging between the technical matters described in the claims and the technical matters of the embodiments or examples. Such correspondence / bridge does not mean that the technical matters described in the claims are interpreted as being limited to the technical matters of the embodiments or the examples.

A back surface inspection apparatus for a lining body according to the present invention comprises: a first vibration receiver (6) joined to a surface side of a lining layer (2) which is a surface side layer of a layered structure; Second joined
A vibrator (7), a vibrator (5) for applying low-frequency vibration to the lining layer (2) that is hardly affected by physical properties of the lining layer (2), and the first vibration receiver (6) ) And a calculator for calculating a transfer function that is a ratio of a first physical quantity and a second physical quantity corresponding to a received signal received by the second geophone (7). The first physical quantity and the second physical quantity are the low frequency ω
The function of The output of the receiver (6, 7) is at time t
Which is converted by a computer into a function of the angular frequency ω by performing a Fourier transform.

[0008] The first geophone (6) and the second geophone (7)
Two different positions from the shaker (5), especially in a straight line
The first physical quantity and the second physical quantity are
The corresponding function v₁(T) and v₂(T). Or
A corresponding to the acceleration ₁(T) and a₂(T)
You. The transfer function is defined as described below. Furthermore,
Phase velocity C of Rayleigh wave_RAs described below
Defined. The difference between the measured value of the phase velocity and the reference value
The back side of the lining layer (2: hereinafter referred to as concrete layer)
Are determined.

In this case, the vibrator (5 = 11) and the first vibrator (6 = 12) are arranged at the same position, and the second physical quantity is a quantity f (t) corresponding to the vibrating force. One physical quantity is a vibration velocity v (t) at a vibration position on the surface side of the lining layer (2). In this case, the transfer function and the spring constant k are defined as described below.

[0010] The lining layer can be illustrated in particular as a concrete layer (2) covering the ground of the tunnel. Since the thickness of the concrete layer is generally 700 mm or less, the excitation frequency is preferably several hundred Hz or less.

[0011] The method for inspecting the back surface of a lining body according to the present invention comprises: vibrating a point-like region on the surface side of a lining layer which is a surface side layer of a layer structure; Or acceleration), calculating each of the Rayleigh wave velocities (phase velocities) based on a plurality of physical quantities, determining a difference between the calculated phase velocities and the reference phase velocities, Rayleigh waves are
Since the low frequency is hardly affected by the physical properties of the lining layer and the thickness of the lining layer is generally 700 mm or less, the low frequency is preferably several hundred Hz or less.

[0012] The method for inspecting the back surface of a lining body according to the present invention is a method of vibrating a point-like area on the surface side of a lining layer, which is a surface side layer of a layer structure; Measuring the vibration velocity of the layer structure, calculating the spring constant of the layer structure from the excitation force and the vibration velocity, and determining the difference between the measured spring constant and the reference spring constant. Since the low frequency is hardly affected by the physical properties of the material and the thickness of the lining layer is generally 700 mm or less, the low frequency is preferably several hundred Hz or less. The spring constant is defined as described above.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Corresponding to the drawings, an embodiment of the backside inspection apparatus for a lining body according to the present invention is based on the physical principle shown in FIGS. FIG. 1 shows a model of a layered structure to which the present principle is applied. Specifically, this model is exemplified by the ceiling of a tunnel. FIG.
Shows a cross section of the tunnel cut along a vertical plane including a center line extending in the horizontal direction.

As shown in FIG. 1, the normal tunnel model includes a back layer 1 that is ground or rock and a concrete layer 2 that is a lining layer that covers the surface side of the back layer 1. In the abnormal tunnel model, a muddy water layer 3 is interposed between the back layer 1 and the concrete layer 2 as shown in FIG.

When the surface side of the concrete layer 2 is vibrated, the physical properties of the Rayleigh wave in the low frequency region are as follows:
It is hardly affected by the physical properties and thickness of the concrete layer 2, and is more strongly affected by the back layer. This has been made clear by the inventors' theoretical analysis. FIG. 3 shows the results of a special numerical calculation under the conditions of the surface excitation of the layered structure based on the propagation theory in which the waves generated in the N (N is a natural number) layered structure are analyzed using the transfer matrix method. . FIG.
And the horizontal axis is the S-wave velocity (m / s) of the bedrock that is the back layer 1
And the vertical axis represents the phase velocity (m / m) of the Rayleigh wave propagating through the layer structure composed of the concrete layer 2 and the back layer 1.
s). The Rayleigh wave phase velocity is a physical quantity calculated from a transfer function described later.

The curve with the larger value of the two curves in FIG. 3 is the normal layer corresponding curve I corresponding to the normal layer structure shown in FIG. The curve with the smaller value of the two curves is the abnormal layer corresponding curve II corresponding to the abnormal layer structure shown in FIG. Thus, it can be seen that the physical quantity defined by the low-frequency transfer function is a physical quantity that is clearly distinguished between the normal layer structure and the abnormal layer structure. By defining two transfer functions, the present inventor analyzed an actual layer structure by applying actual parameters to theoretical equations.

Rayleigh wave velocity method: The Rayleigh wave velocity method named by the present inventors uses the following transfer function 1. Transfer function 1: Rayleigh wave phase velocity is calculated from the transfer function. FIG. 4 shows a measuring device for measuring a physical quantity defining the transfer function. Defects 4 such as puddles and cavities may exist between the back layer 1 and the concrete layer 2. The measuring device includes a vibrator 5, a first vibrator 6, and a second vibrator 7. Exciter 5
Is a conventional means for applying a sinusoidal excitation force to the concrete layer 2. The vibrator 5 generates a low frequency of several hundred Hz or less. If the thickness of the concrete layer 2 is about 500 mm, the separation distance between the exciter 5 and the first receiver 6 is 1
It is appropriate that the distance is about 0 m. In this case, it is appropriate that the separation distance between the first geophone 6 and the second geophone 7 is about 1 m.

FIG. 5 shows a circuit block of the measuring system. The first geophone 6, which is a kind of accelerometer, detects the vibration of the portion of the concrete layer 2 where the first geophone is placed and outputs a _first vibration waveform signal v ₁ (t). The first received waveform signal v ₁ (t) that can be extracted as a time-series voltage signal is
It is an electric signal corresponding to the speed (including speed data of Rayleigh wave). The second geophone 7, which is a kind of accelerometer, detects the vibration of the portion of the concrete layer 2 on which it is arranged and outputs a _second vibration waveform signal v ₂ . Second received waveform signal v ₂ that can be extracted as a time-series voltage signal
(T) is an electric signal corresponding to speed (including speed data of Rayleigh wave).

The first received waveform signal v ₁ (t) and the second received waveform signal v ₂ (t) are input to the FFT analyzer 8. The FFT analyzer 8 is a conventional means for converting a signal waveform into a data signal having the angular frequency ω as a variable. First received waveform signal v ₁ (t) and second received waveform signal v ₂ (t)
Is Fourier transformed by the FFT analyzer 8, and V
₁ (ω) and V ₂ (ω). Transfer function H (ω)
Is defined by the following equation: H (ω) = V ₂ (ω) / V ₁ (ω) Using this transfer function, the following physical quantity _CR is defined. C _R is called a phase velocity of the Rayleigh wave. C _R = ω ₀ L / Arg [H (ω ₀ )] Here, ω ₀ is a frequency used. L is the separation distance between the first geophone 6 and the second geophone 7, and L can be measured with high accuracy by attaching a laser length measuring device or the like to the geophone.

The vibrating force given by the vibrator 5 propagates in the medium consisting of the back layer 1 and the concrete layer 2. When the excitation frequency is low, Ra propagating in the surface region
Yleigh waves are hardly affected by the physical properties of the concrete layer 2 and largely depend on the geology of the back rock as the back layer 1. As shown in FIG. 3, rock S-wave velocity and Ray
The relationship between the phase velocities of the S-wave of the light wave is largely unaffected by the physical properties of the concrete layer 2 and largely depends on the physical properties of the back layer 1. If the defect 4 shown in FIG. 4 exists on the side of the back layer 1, the S ray of the Rayleigh wave is greatly affected by the defect 4 which is the back layer. The effect is due to the transfer function H
Appears at (ω). omega ₀ and L is is constant regardless of the presence or absence of defects 4, in response to the presence or absence of defects 4, appears clear difference in phase velocities C _R described by both the transfer function H (ω). FIG. 3 shows the range of the Rayleigh wave fluctuation when the physical property value of the concrete layer 2 fluctuates by 10% in the positive and negative directions.
The differences are clearly evident, as indicated by the error bars in FIG. Area defect 4 is not present, so overwhelmingly large relative area existing defect 4, by performing measurements at multiple locations, C _R region having no defect 4 is estimated with ease reliably obtain. C estimated so
_R is set as a reference value for determining whether or not the defect 4 exists.

Spring constant method: The following transfer function 2 is used in the spring constant method named by the present inventors. Transfer Function 2: FIG. 6 shows a measuring device for measuring the transfer function. Defect 4 may be present between back layer 1 and concrete layer 2. The measuring device is a shaker 11
And a geophone 12. The shaker 11 is
This is a conventional means for applying a sinusoidal excitation force to the concrete layer 2. The vibrator 11 generates a low frequency of several hundred Hz or less. Suitably, the separation distance between the exciter 11 and the receiver 12 is substantially zero.

FIG. 7 shows a circuit block of the measurement system. The vibrator 11 applies a vibrating force to the concrete layer 2. The vibrator 11 generates a voltage signal f corresponding to the vibrating force.
(T) is output. Geophone 12 which is a kind of accelerometer
Detects the vibration speed of the portion of the concrete layer 2 where it is disposed and outputs a received waveform signal v (t).

Exciting force signal f (t) and received waveform signal v
(T) is input to the FFT analyzer 13. FFT
The analyzer 13 is the same as the analyzer described above.
Fourier transform into a data signal with frequency ω as a variable
Means. Exciting force signal f (t) and received waveform signal v
(T) is F (ω) and V
(Ω). A transmission called mechanical impedance
The arrival function H (ω) is defined by the following equation. H (ω) = F (ω) / V (ω) Using this transfer function, the following physical quantity k is defined.
You. k is called the spring constant by the present inventors. k = −Im [H (ω₀)] × ω₀  Where ω₀Is the angular frequency used. Im the machine
2 shows an imaginary part of a transfer function which is a mechanical impedance. FIG.
In curves I and II, the values according to this definition are used.
You. The horizontal axis in FIG. 8 is the same as the horizontal axis in FIG. 3, and the vertical axis is
The spring constant k (N / m) is shown.

The vibrating force applied by the vibrator 11 propagates through the medium consisting of the back layer 1 and the concrete layer 2.
At low frequencies, the spring constant k is largely unaffected by the physical properties of the concrete layer 2 and largely depends on the physical properties (S-wave velocity) of the back layer 1. When the defect 4 shown in FIG. 6 is present on the side of the back layer 1, the effect thereof is as shown in FIG.
Appears at (ω). Since ω ₀ is constant regardless of the presence or absence of the defect 4, both transfer functions H
A clear difference appears in the two spring constants k described by (ω). If there is a back defect, the spring constant is significantly reduced.

[0025]

FIG. 9 shows the values of a plurality of parameters used in the theoretical analysis shown in FIGS. Although the case of applying a sinusoidal excitation force is described in both methods, an inspection by impact excitation can be performed. In the Rayleigh wave velocity method, the difference Δ between the initial movement times in the vibration velocity waveforms v ₁ (t) and v ₂ (t) or the vibration acceleration waveforms a ₁ (t) and a ₂ (t) between the geophone 6 and the geophone 7.
By dividing the t at distance L, to calculate the Rayleigh wave velocity _{C R (C R = Δt /} L). In the spring constant method, in the limit that brings ω ₀ close to zero,

(Equation 1) And calculate k. The present invention can be effectively applied not only to the top of the tunnel but also to the inspection of its side. Inspection along the curved surface of the tunnel can be applied to the above-described embodiment almost as it is, and can also be applied to the embankment, the quay, the embankment, and the cliff.

[0026]

According to the back surface inspection apparatus and the back surface inspection method for a lining body according to the present invention, a highly reliable inspection method can be established. Specifically, it is theoretically clear that the use of low-frequency elastic waves makes it possible to identify the S-wave velocity of the medium on the backside of the uncovered surface without being affected by the physical properties and layer thickness of concrete. Was done. The presence or absence of a defect on the back surface caused a significant difference in the Rayleigh wave (phase) velocity and the ground spring constant, and it was theoretically clarified that abnormality detection was possible. Both of these methods, whose theoretically high reliability is evident, can appropriately deal with a wide range of screening tests and one-point spot tests, respectively.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing an apparatus for inspecting a back surface of a lining body according to the present invention and a model to be inspected by a method of inspecting the back surface thereof.

FIG. 2 is a cross-sectional view showing another inspection object model of the back surface inspection apparatus and the back surface inspection method of the lining body according to the present invention.

FIG. 3 is a graph showing the results of a theoretical analysis.

FIG. 4 is a sectional view showing a model to be inspected and a measuring apparatus in the method for inspecting the back of a lining body according to the present invention.

FIG. 5 is a circuit block diagram showing a circuit of the measuring device.

FIG. 6 is a cross-sectional view showing a model to be inspected and another measuring device in the method for inspecting the back of a lining body according to the present invention.

FIG. 7 is a circuit block diagram showing a circuit of another measuring device.

FIG. 8 is a graph showing the results of a theoretical analysis.

FIG. 9 is a table showing parameters used for theoretical analysis.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Back layer 2 ... Lining layer (concrete layer) 5 ... Exciter 6 ... 1st geophone 7 ... 2nd geophone

Claims (12)

[Claims] A first vibration receiver joined to a surface side of a lining layer which is a surface side layer of the layer structure; a second vibration receiver joined to the surface side; A vibrator applied to the layered structure from the surface side of the working layer, and a computer for calculating a transfer function that is a ratio of a first physical quantity and a second physical quantity received by the first and second geophones. And a back surface inspection device for a lining body. 2. The device according to claim 1, wherein the first geophone and the second geophone are linearly arranged at two different positions from the exciter, and the first physical quantity and the second physical quantity are respectively The back surface inspection device for the lining body, which has functions v ₁ (t) and v ₂ (t) corresponding to the speed. 3. The device according to claim 1, wherein the first geophone and the second geophone are linearly arranged at two different positions from the exciter, and the first physical quantity and the second physical quantity are respectively A back surface inspection apparatus for a lining body, which includes functions a ₁ (t) and a ₂ (t) corresponding to acceleration. 4. The method of claim 2, wherein the transfer function is defined by _{V 2 (ω) / V 1} (ω), the phase velocity _{C R} of Rayleigh wave _{equation: C R = ω 0 L /} Arg [H (Ω ₀ )], wherein L is a distance between the first geophone and the second geophone, and a difference between a measured value of the phase velocity and a reference value indicates a distance between the back surface of the lining layer and the reference value. A back surface inspection device for linings that determines the difference in circumstances. 5. The method of claim 3, wherein the transfer function is defined by _{A 2 (ω) / A 1} (ω), the phase velocity _{C R} of Rayleigh wave _{equation: C R = ω 0 L /} Arg [H (Ω ₀ )], wherein L is a distance between the first geophone and the second geophone, and a difference between a measured value of the phase velocity and a reference value indicates a distance between the back surface of the lining layer and the reference value. A back surface inspection device for linings that determines the difference in circumstances. 6. A first vibration receiver joined to a surface side of a lining layer, which is a surface side layer of the layer structure, and applying low frequency vibration to the layer structure from the surface side of the lining layer. A vibrator; and a calculator for calculating a first physical quantity f (t) corresponding to a vibrating force of the vibrator and a second physical quantity v (t) received by the first vibrator. A back surface inspection apparatus for a lining body in which a difference in a state of a back surface of the lining layer is determined based on one physical quantity f (t) and the second physical quantity v (t). 7. The method according to claim 6, wherein the transfer function is defined as H (ω) = V (ω) / F (ω), where F (ω) = F [f (t)], V (ω ) = F [v
(T)], and F [] denotes a Fourier transform, and a spring constant k is defined by the following equation: k = −Im [H (ω ₀ )] × ω ₀ , and a measured value of the spring constant k and a reference A back surface inspection apparatus for a lining body in which a difference in a state of a back surface of the lining layer is determined based on a difference between the value and the value. 8. The back surface inspection apparatus for a lining body according to claim 1, wherein the lining layer is a concrete layer covering the ground of a tunnel. 9. The back surface inspection apparatus according to claim 8, wherein the low frequency is several hundred Hz or less. 10. Exciting a point-like area on the surface side of a lining layer, which is a surface-side layer of a layer structure, a plurality of Rayleighs measured at a plurality of points on the surface side.
Calculating the phase velocities of the waves respectively, including determining the difference between the calculated phase velocities and the reference phase velocities, the Rayleigh waves are low frequencies that are hardly affected by the physical properties of the lining layer, A method for inspecting a back surface of a lining body, wherein the low frequency is several hundred Hz or less. 11. Exciting a point-like region on the surface side of a lining layer which is a surface side layer of a layer structure, and measuring a spring constant of the layer structure from the physical quantity and an exciting force by the excitation. Determining the difference between the measured spring constant and the reference spring constant, wherein the elastic wave is a low frequency that is hardly affected by the physical properties of the lining layer, and the frequency of the low frequency is several hundred Hz. The following is the method of inspecting the back of a lining body. 12. The method according to claim 10, wherein the lining layer is a concrete layer.