JP4332479B2 - Harbor structure diagnosis method - Google Patents

Description

  The present invention relates to a harbor structure diagnosis method capable of diagnosing cavities and voids of caisson breakwaters.

  Breakwaters are constructed for the purpose of protecting port, city, industrial facilities and other activities from waves, storm surges and tsunamis. The breakwater keeps the harbor calm and allows safe navigation, anchoring and cargo handling of the ship. As shown in FIG. 15, most of Japan's breakwaters are provided with a mound 11 made of stone on the submarine ground 100, and a vertical dam body (caisson means cask in French) 10 is installed on it. FIG. 15A is a plan view of the caisson, and FIG. 15B is a cross-sectional view of the caisson 10 along the cross section (HH) in FIG.

  There is also a wave-dissipating block-covered embankment where a wave-dissipating block (not shown) is placed in front of the caisson 10 for the purpose of reducing wave power at points where waves are large. Hereinafter, the breakwater 200 is collectively referred to. The caisson 10 has a structure in which sand 12 is filled (this is referred to as medium-packed sand), covered with lid concrete 13 (unreinforced), and upper concrete 14 is further disposed thereon. . The lid concrete 13 and the upper concrete 14 are formed in close contact with each other.

  Usually, the breakwater caisson 10 is divided into appropriate small sections by a partition wall 16 and is 12 m × 15 m in a plane, and the height varies depending on the water depth. Due to wave erosion for many years, the wave-dissipating block may scrape the side wall of the caisson 10 and the filling sand 12 may flow out. Further, the caisson 10 itself may be broken by the scouring of the mound 11 or the uneven settlement of the foundation ground 100. When the inside sand 12 of the caisson 10 flows out, the upper part becomes relatively heavy, so that it becomes unstable mechanically. The caisson 10 itself moves and slides depending on the outflow amount of the filling sand 12, and in the worst case, the caisson 10 may be destroyed.

  As described above, when a void or cavity 15 is generated in the caisson 10, the breakwater 200 may be destroyed. Therefore, in order to maintain the breakwater 200 in a stable normal state, the cavity 15 is provided inside the caisson 10. It is necessary to investigate and confirm whether or not voids are generated.

  In order to investigate the cavities and voids in the breakwater 200, a method of excavating a borehole from the surface of the upper concrete 14 and observing the height up to the filling sand 22 by inserting a waterproof camera is performed. The survey was costly and time consuming.

  In addition, in order to investigate non-destructively and efficiently the cavity on the back of the concrete structure (the bottom surface of the lid concrete in FIG. 15B), a ground penetrating radar using a pulse wave is used. Since the surveyable depth is about 1 m and the concrete thickness in the breakwater 200 is 4 m or more, it cannot be probed by a conventional pulse wave underground radar.

  In order to eliminate such drawbacks of the prior art, for example, a continuous wave (FM-CW) that can handle a continuous wave (CW: Frequency Modulation) in the same way as an electromagnetic pulse. ) Type ground penetrating radar is used to investigate cavities with a concrete thickness of 4 m or more.

Another example is a structure diagnostic apparatus proposed by the present inventor (see Non-Patent Document 1). Further, the inventors of the present application have already proposed the continuous wave type underground radar exploration used here (see Non-Patent Document 2).
“Photoelectric Technical Bulletin” No. 18, P2-4 “Development of Harbor Structure Diagnosis Device” issued on July 31, 2002 from Koden Manufacturing Co., Ltd. “Geological News No. 537”, pages 44-52, issued by the Geological Survey of Japan Institute of Technology on May 1, 1999, “Groundland radar exploration using a stepped continuous wave radar exploration device”

  However, when such a subsurface radar determines the presence or absence of a cavity in a harbor structure, there are large individual differences due to differences in the experience and results of subsurface radar engineers. For example, based on the judgment of the engineer in charge that “there is a cavity”, when a boring survey is performed on the target breakwater to actually confirm the existence of the cavity, the cavity may not exist. Moreover, depending on the judgment of an unfamiliar engineer, the void may be lost.

  An object of the present invention is to provide a harbor structure diagnosis method capable of automatically detecting the existence state of a cavity from a frequency spectrum and a waveform profile obtained by measurement with high reliability.

In order to achieve this object, the harbor structure diagnosis method according to the present invention is such that continuous wave electromagnetic waves radiated from the surface of the harbor structure to be diagnosed are emitted from the harbor structure. Receive the reflected wave reflected,
Calculating the frequency spectrum contained in the reflected wave;
The frequency spectrum level in the frequency range of interest (for example, 5 to 18 MHz) of the frequency spectrum exceeds a predetermined level, and the peak frequency of the frequency spectrum is approximately the center value of the frequency range of interest (for example, 10 MHz) and the peak width is determined to be wider than a predetermined frequency width (for example, a frequency width in the vicinity of 4.2 MHz), a predetermined thickness (for example, thickness) in the harbor structure It is configured to determine that there may be a thick cavity of 30 cm or more.

In addition, from the surface of the harbor structure to be diagnosed, a continuous wave electromagnetic wave radiated to the harbor structure receives a reflected wave reflected from the harbor structure,
Calculating the frequency spectrum contained in the reflected wave;
The frequency spectrum level in the frequency range of interest (for example, 5 to 18 MHz) of the frequency spectrum exceeds a predetermined level, and the peak frequency of the frequency spectrum is approximately the center value of the frequency range of interest (for example, 10 MHz) or when the peak frequency of the frequency spectrum is lower than the approximate median of the frequency range of interest and the peak width is a predetermined frequency width (for example, a frequency width in the vicinity of 4.2 MHz). ) When it is determined to be narrower, it is determined that there is a possibility that a thin cavity having a thickness less than a predetermined thickness (for example, 30 cm in thickness) may exist in the harbor structure.
Further, it is determined whether or not the phase of the time waveform of the reflected wave is inverted. When the phase of the time waveform is “inverted”, the cavity is filled with air, and the phase of the time waveform is It can be configured to determine that the cavity is filled with seawater when “no inversion”.
In addition, when the phase of the time waveform of the reflected wave is “with inversion” and the harbor structure is below the sea level, there may be voids in the upper concrete of the harbor structure. It can be configured to determine that there is a sex.

ADVANTAGE OF THE INVENTION According to this invention, the detection capability of the cavity produced in a breakwater can be improved significantly.
As a result of the judgment, a result report is made into a database, and the secular change of the caisson internal state can be grasped.
According to the present invention, it is possible to quantitatively maintain a harbor structure centering on the caisson breakwater, and its practical effect is extremely large.

  The present invention will be described below with reference to the drawings.

FIG. 1 is a system diagram showing an arrangement example of measuring apparatuses used in the present invention. This measuring device is arranged on the surface of the upper concrete 14 arranged on the upper part of the caisson 10. Here, the transmitter (Tx) 1 includes a transmission antenna, a transmitter, a frequency conversion circuit to an AF (Audio Fraquency) band, and an E / O.O / E (electric / optical / optical / electrical) converter. , An A / D / D / A converter, and a battery for driving them. The reception unit (Rx) 2 includes reception antennas 2-1 and 2-2, a reception unit, an E / O / O / E converter, and a battery. The measurement device can be controlled by a personal computer (not shown) connected to the measurement device. As shown in FIG. 1, two receiving antennas 2-1 and 2-2 are used to improve S / N by superimposing reflected waves from the cavity 15, but this is not an essential requirement. It is also possible to use a single or three receiving antennas.
The antennas are connected with an E / O converter and an optical fiber cable (analog link) connected to the output of the O / E converter in order to avoid inductive noise. An optical cable (digital link) is also used to transmit control signals and recorded data from a personal computer. The upper part of each antenna is subjected to shielding treatment with ferrite to absorb electromagnetic waves radiated upward and to block external noise.

  FIG. 2 shows a numerical model set for computer simulation in order to determine the measurement result of the ground penetrating radar. In this model, the total thickness of the upper concrete 14 and the lid concrete 13 shown in FIG. 1 is 4.3 m, and the thickness of the air layer shown above the upper concrete 14 is 0.1 m. -1 and each of the receiving antennas 2-1 and 2-2 and the upper concrete 14 is a thickness of the gap. As examples of the thickness of the cavity filled with air or seawater, 50 cm, 100 cm, and 200 cm are shown. The width of the caisson is 24 m.

In the measurement system shown in FIG. 1, when a continuous wave type electromagnetic wave is radiated from the transmitting antenna 1-1 of the transmitting unit 1 placed on the surface of the upper concrete 14 disposed on the upper side of the caisson 10, the concrete (13, 14) The electromagnetic waves propagated in the interior are reflected at the boundary between the concrete 13 and the filled sand 12 or the concrete 13, 14 and the cavity 15.
The reflected waveform of the electromagnetic wave is calculated based on the electromagnetic wave equation.
The reflected electromagnetic waves are captured by the receiving antennas 2-1 and 2-2 of the receiving unit 2 placed on the surfaces of the upper concrete 13 and 14.
The receiving unit 2 arranges the waveforms in the same manner as the measurement of the ground radar and creates a waveform profile.
At the same time, an amplitude spectrum is calculated using Fourier transform to create a spectrum profile.

FIG. 3 is a frequency spectrum obtained by computer simulation when there is no cavity. An output appears at a frequency of 12 to 40 MHz.
FIG. 4 is a frequency spectrum obtained by computer simulation when the inside of the cavity is air.
FIG. 5 is a frequency spectrum obtained by computer simulation when the inside of the cavity is seawater.
Comparing the above three cases, it can be seen that the output appears between 5 and 18 MHz in the case of FIG.
When the thickness of the cavity 15 is changed, the peak of the amplitude spectrum shifts to a frequency lower than the approximate median value (about 10 MHz) of the frequency range (5 to 18 MHz) as the thickness of the cavity increases regardless of the material in the cavity. .

On the other hand, the waveforms in the computer simulation are reversed in phase when the cavity 15 shown in FIG. 6 is air and when the cavity 15 shown in FIG. 7 is seawater.
By determining by combining these phenomena, the presence / absence of a cavity, the substance in the cavity, and a certain size of the cavity can be determined.

From the result of computer simulation, when there is a cavity, the output of the frequency spectrum appears between 5 and 18 MHz, and when the cavity becomes thick, the peak of the frequency spectrum is approximately the center value (about 10 MHz) of the frequency range (5 to 18 MHz). ) It is observed that the frequency shifts to a lower frequency side. Thus, from the measurement result, the frequency range that seems to directly affect the determination of whether or not the measurement object is correct is the frequency range of interest of the frequency spectrum.
On the other hand, in the waveform profile, it is recognized that the phase of the reflected wave is reversed between air and seawater.

Next, actual measurement data will be described.
FIG. 8 is an amplitude spectrum of a continuous wave underground radar obtained on an actual breakwater, and has a peak at 10 MHz or less, and thus there may be a cavity. In the case of FIG. 8, the peak width of 10 MHz or less is about 5 MHz in terms of the peak width at the 70% value (about 4.7) of the peak value (about 6.7).
When this site was excavated, a cavity filled with seawater was detected.

FIG. 9 is the same as FIG. 8, but the peak width between 5 and 18 MHz of the frequency spectrum is about 3.5 MHz according to the same criteria as in FIG. 8, and thus is narrower than the case of FIG. 8 (5 MHz). The frequency range.
When excavating this spot, a void filled with air was detected in the concrete.
Therefore, judging from the measurement results of FIG. 8 and FIG. 9, when the peak width is 5 MHz when viewed from the above criteria, it is a thin cavity filled with seawater and when the peak width is 3.5 MHz, it is a thin cavity filled with air Therefore, whether the cavity is filled with seawater or air can be determined based on whether the peak width is wider or narrower than the intermediate peak width (for example, the peak width in the vicinity of 4.25 MHz). This criterion may be determined appropriately by examining the on-site measurement results for the prescribed object.

10 and 11 show reflected output waveforms corresponding to FIGS.
In FIG. 10 and FIG. 11, the phase of the waveform is inverted, which matches the result of the computer simulation.

FIG. 12 summarizes the above determination as a diagnosis flow.
The operation flow in this case is roughly as follows.
After starting the operation (S0), paying attention to the spectrum output of the frequency of 5 to 18 MHz with reference to the spectrum profile (S1), the spectrum output reaches a preset level (for example, about 10% of the maximum spectrum value). A peak detection test is performed (S2). When the test in S2 is YES, the following processing is performed according to whether the peak frequency of the frequency spectrum is higher or lower (S3-1, S3-2)). In this test, when the peak frequency is determined to be “low” in the range (5 to 10 MHz) lower than the approximate median value (10 MHz) within the focused frequency band (5 to 18 MHz) (S3-1), Further, it is tested whether the peak width is wider or narrower than, for example, a predetermined peak width in the vicinity of 4.25 MHz (S4). In the test of step S4, when it is determined that “the peak width is wide”, the reflected wave phase is next referred to (S5-1), and the reflected wave phase is positive (no inversion) or negative (with inversion). ) Test is performed (S6-1). In addition, the test of S2 is YES, and the peak frequency is determined to be “high” in the range (10 to 18 MHz) higher than the approximate median value (10 MHz) within the frequency band (5 to 18 MHz) of interest. When it is determined that the peak width is narrow in the test of step S4 (S3-2), the waveform of the reflected wave is further inverted with reference to the waveform of the reflected wave (S5-2). A test is performed to determine whether there is "none (positive)" or "with inversion (negative)" (S6-2). If the caisson crest is above the sea level, the cavity is filled with air (see FIG. 15). If the caisson crest is below sea level, the cavity is filled with sea water. However, the phase of the waveform may be reversed even though the top of the caisson is below sea level. When excavating here, a void (filled with air above sea level) was found inside the upper concrete, which is thought to be the cause of the phase inversion of the waveform. From this fact, if the phase of the waveform is reversed even when the caisson crest is below the sea level, it is diagnosed as a void inside the upper concrete. In order to confirm this fact, it is tested whether the caisson is above or below the sea level (S7-1) and (S7-2).

Based on the results of the above test, the state of the cavity is determined as follows (S8).
(S8-1-1) In the test in S6-1, it is determined that the phase of the reflected wave is positive when the peak frequency is in a frequency range lower than the approximate median value in the focused frequency band (5 to 18 MHz). When it is determined, “there is a possibility of a thick cavity filled with seawater (thickness of 30 cm or more)”.
(S8-1-2) It is determined that the peak frequency is in a frequency range lower than the approximate median value in the focused frequency band (5 to 18 MHz) and the phase of the reflected wave is negative in the test in S6-1. When it is determined, “there is a possibility of a thick cavity filled with air (thickness of 30 cm or more)”.
(S8-2-1) The peak frequency is in a frequency range higher than the approximate median value in the focused frequency band (5 to 18 MHz), and in the test in S6-2, the phase of the reflected wave is “no inversion ( "Correct)" is determined, it is determined that "a thin cavity filled with seawater (thickness less than 30 cm) may exist".
(S8-2-2) The peak frequency is in a frequency range higher than the approximate median value in the focused frequency band (5 to 18 MHz). In the test in S6-2, the phase of the reflected wave is “inverted (negative) ) ”, It is determined that“ a thin gap filled with air (thickness less than 30 cm) may be present ”.
(S8-3) In the test of S7-1 and S7-2, when it is determined that the caisson is below the sea level, it is determined that “there is a gap inside the upper concrete”.
(S8-4) In the test in S2, when it is found that the frequency spectrum in the frequency band of 5 to 18 MHz does not reach the predetermined level (S3-3), it is determined that there is no cavity.

  From the above, in the waveform profile, it is possible to determine whether the interior of the cavity is filled with seawater or air by determining the phase of the reflected wave from the cavity.

In order to automate this diagnosis flow, calculation is performed by a computer according to the analysis procedure shown in FIG.
The outline of the operation in this case is as follows.
First, a folder for working (setting a work area) (S11).
The input file and input / output parameters (upper concrete thickness, electromagnetic wave velocity, caisson power) are measured (S12).
These data can be input in a batch process on the same screen (S13).
Next, the inputted input / output parameter is confirmed (S14).
For the amplitude, a threshold value is determined using the standard deviation (S15).
Next, the data is averaged and normalized (S16).
Here, 1) calculation of spectrum peak level, 2) calculation of spectrum peak frequency, 3) calculation of spectrum peak width, and 4) phase detection of waveform (S17).
Based on the calculation result in S17, diagnosis according to the diagnosis flow described with reference to FIG. 12 is performed (S18).
Next, the diagnostic result report is displayed and stored (S19), and the operation is terminated (S20).

A comment such as a measurement location / date is input as the calculated result, and the result is output and stored in a result display report illustrated in FIG. Here, numerical data (diagnostic parameters, diagnostic result numerical values, result diagrams) and the like are shown in the lower frame.
The “form file name” in the last row of the upper frame is a file name for saving the main result in the result report in a text format so that it can be converted into a database.

  It is possible to detect the location and size of cavities generated in harbor structures such as breakwaters and the intrusion state of seawater with high reliability, so it can be applied as an important means for maintenance of harbor structures. .

It is a cross-sectional schematic diagram for demonstrating the apparatus arrangement | positioning for implementing this invention method. It is sectional drawing which shows the model of the computer simulation applied to this invention. It is a frequency spectrum characteristic example figure by computer simulation when there is no cavity. It is a frequency spectrum characteristic example figure by computer simulation in the case where the cavity filled with air exists. It is an example of the frequency spectrum characteristic by computer simulation when the cavity filled with seawater exists. It is an example of a reflected waveform by computer simulation when there is a cavity filled with air. It is an example of a reflected waveform by computer simulation when there exists a cavity filled with seawater. It is an example figure of a frequency spectrum characteristic by actual measurement data when there is a cavity filled with air. It is a frequency spectrum characteristic example figure by actual measurement data when the cavity filled with seawater exists. It is an example of a reflected waveform by actual measurement data when there is a cavity filled with air. It is an example of a reflected waveform by actual measurement data when there is a cavity filled with seawater. It is an example figure of a cavity diagnosis flow by the method of the present invention. It is a flowchart which shows the example of an analysis procedure by this invention method. It is a display example figure of the diagnostic result report obtained by the method of the present invention. It is the top view (a) and longitudinal cross-sectional view (b) which show the structural example of the breakwater caisson which is a diagnostic object of this invention method.

Explanation of symbols

1 Transmitter (Tx)
1-1 Transmitting antenna 2 Receiver (Rx)
2-1, 2-2 Receiving antenna 10 Caisson 11 Mound 12 Filled sand 13 Cover concrete 14 Upper concrete 15 Cavity 16 Bulkhead 100 Submarine ground 200 Breakwater

Claims (3)

The harbor structure is a caisson breakwater,
From the surface of a diagnosis target the port structures, continuous wave electromagnetic wave method radiated against該港bay structure, it receives a reflected wave reflected from該港Bay structure,
Calculating the frequency spectrum contained in the reflected wave;
Of the frequency spectrum, the level of the frequency spectrum in the frequency range of interest exceeds a predetermined level, the peak frequency of the frequency spectrum is lower than the approximate center value of the frequency range of interest, and the peak width is predetermined. When it is determined that it is wider than the frequency width, it is determined that there is a possibility that a thick cavity of a predetermined thickness or more exists in the harbor structure ,
Further, it is determined whether or not the phase of the time waveform of the reflected wave is inverted. When the phase of the time waveform is “inverted”, the cavity is filled with air, and the phase of the time waveform is A harbor structure diagnosis method characterized by determining that the inside of a cavity is filled with seawater when "no reversal". The harbor structure is a caisson breakwater,
From the surface of a diagnosis target the port structures, continuous wave electromagnetic wave method radiated against該港bay structure, it receives a reflected wave reflected from該港Bay structure,
Calculating the frequency spectrum contained in the reflected wave;
When it is determined that the level of the frequency spectrum in the frequency range of interest out of the frequency spectrum exceeds a predetermined level and the peak frequency of the frequency spectrum is higher than the approximate median value of the frequency range of interest, or When it is determined that the peak frequency of the frequency spectrum is lower than the approximate median of the frequency range of interest and that the peak width is narrower than a predetermined frequency width, a thin cavity having a thickness less than a predetermined thickness in the harbor structure Is likely to exist ,
Further, it is determined whether or not the phase of the time waveform of the reflected wave is inverted. When the phase of the time waveform is “inverted”, the cavity is filled with air, and the phase of the time waveform is A harbor structure diagnosis method characterized by determining that the inside of a cavity is filled with seawater when "no reversal". When the phase of the time waveform of the reflected wave is “with inversion” and the harbor structure is below the sea level, there is a possibility that a void exists in the upper concrete of the harbor structure. The harbor structure diagnosis method according to claim 1 , wherein the harbor structure diagnosis method is determined.

Images