JP2006153505A - Detection method of internal cracking of structure - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To detect not only the cracking produced in a structure but also a precise change in cracking in real-time and to reduce the damage applied to the structure. <P>SOLUTION: A drilled hole 26 is formed to a wall part 12 from the direction crossing the direction in which cracking 24 will occur using a hammer drill 2 or the like, and a pipe 28 made of metal is inserted in the deep part of the drilled hole 26 to be fixed to the deep part. The shaft-like detection part 30 is inserted in the inner periphery of the drilled hole 26 and its leading end is inserted in the hole of the pipe 28. The part where the detection part 30 is positioned to the wall surface 22 of the drilled hole 26 of is fixed to the wall surface 22 in an immovable manner. The relative displacement along the drilling direction of the drilled hole 26 to the part of a block 14, to which the wall surface 22 and the pipe 28 are fixed, is measured by the detection circuit 32 connected to the detection part 30. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for detecting cracks generated inside a structure.

There are structures constructed by filling joint materials such as plaster and mortar between blocks such as stone, brick and concrete blocks.
In such a structure, a crack may occur in the joint due to an external force.
Among such cracks, cracks occurring at joints facing the outer surface of the structure can be confirmed by visual observation, but cracks occurring inside the structure cannot be visually observed.
Therefore, for cracks that cannot be visually observed, a method of detecting cracks by transmitting ultrasonic waves inside the structure and receiving reflected ultrasonic waves (see, for example, Patent Document 1) or Cracks are identified by nondestructive inspection methods such as sound method and electromagnetic radar method. However, with such a non-destructive inspection method, it is difficult to measure the size of a crack in mm units or to detect a change in crack in real time.
In addition, a circular core having a diameter of about 100 mm is drilled in the structure, the inside of the structure is observed from the hole, and the strength of the structure is determined by the strength of the circular core as a sample obtained by drilling. There are known methods for estimating or analyzing the component of a holed piece, but this method requires damage to the holed hole because it damages the structure.
In addition, a method has been proposed in which a position sensor or displacement meter that detects the position or displacement of the structure is installed at the outer surface of the structure to constantly measure the displacement (movement) of the structure. It only stays in the displacement.
In addition, there is a method of measuring the strain inside the structure by embedding a sensor (strain gauge) that measures the strain (length change) inside the structure, but in this method the sensor is embedded in the structure. Therefore, since a sensor is required for each measurement location, there is a disadvantage that the cost increases.
JP-A-8-178903

Therefore, the above-described nondestructive inspection method is disadvantageous in detecting crack changes precisely and in real time, and the method of drilling a circular core as a sample is disadvantageous in that it damages the structure. The method using a sensor or a displacement meter is disadvantageous in that it cannot detect cracks.
The present invention has been made in view of such circumstances, and its purpose is to detect cracks generated in the structure and to detect changes in the cracks precisely and in real time, and to the structure. It is an object of the present invention to provide a method for detecting cracks in a structure, which requires less damage and is advantageous in reducing costs.

To achieve the above object, the present invention provides a method for detecting cracks in a structure,
Drilling a hole to penetrate the predicted cracked part from the direction intersecting the direction of the crack in the predicted cracked part, fixing a metal pipe at the back of the hole, Insert the shaft-shaped detection part into the inner periphery of the hole and insert the tip into the hole of the pipe, and fix the part of the detection part located on the surface of the structure where the hole is opened. In addition, a change amount that changes according to a relative position along the drilling direction of the drilling hole of the pipe with respect to the detection unit is detected via the detection unit, and the change detected by the detection unit The crack is detected by measuring the relative displacement along the drilling direction of the drilling hole between the surface of the structure and the portion of the structure to which the metal pipe is fixed from the amount. Features.

Therefore, by measuring the relative displacement along the drilling direction of the drilling hole between the surface of the structure and the portion of the structure to which the metal pipe is fixed from the amount of change detected by the detection unit, In addition to detecting cracks that have occurred in the inside of the steel plate, changes in the cracks can be detected precisely and in real time, and the diameter of the hole can be inserted into a metal pipe and a detector inserted through the inner circumference of the pipe Since the dimensions are sufficient, unlike the conventional method of drilling a circular core, damage to the structure can be reduced.
Also, unlike the case where a conventional sensor is embedded in a structure and the strain of the structure is measured, the detection unit is not embedded in the structure, so when the measurement with one hole is completed, the detection unit can be removed and separated. Since it is possible to carry out the measurement by carrying the detection part to the hole, it is advantageous to reduce the number of detection parts and to reduce the cost.

  The metal pipe is fixed to the inner part of the drilled hole drilled so as to penetrate the predicted cracked part from the direction intersecting the direction of the crack in the predicted cracked part, and the holed hole is opened. A portion of the detection unit located on the surface of the structure is fixed, and a hole is formed between the surface of the structure and the portion of the structure on which the metal pipe is fixed based on the amount of change detected by the detection unit. The above object was achieved by measuring the relative displacement along the direction of drilling and detecting cracks.

Next, Embodiment 1 of the present invention will be described with reference to the drawings.
1 is an explanatory diagram of a wall structure of a tunnel, which is a structure to which the method of the present invention is applied, FIG. 2 is an enlarged view of a main part of FIG. 1, and FIG. 3 is a cross-sectional view taken along line AA of FIG.
FIG. 4 is an explanatory diagram showing the process of drilling a hole in the structure, FIGS. 5A and 5B are explanatory diagrams of the hole formed in the structure, and FIG. 6 is a diagram of the hole formed in the structure. FIG. 7 is an explanatory diagram showing a state in which the detection unit is fixed to the drilled hole, FIG. 8 is an explanatory diagram of detection operation by the detection unit, and FIG. 9 is a detection unit and a detection circuit. FIG. 10 is a circuit diagram illustrating a part of the detection circuit, and FIG. 11 is a signal waveform diagram illustrating the operation of the detection unit and the detection circuit.

First, the structure of the wall portion of the tunnel, which is a structure to which the method of the present invention is applied, will be described.
As shown in FIGS. 1 and 2, the wall portion 12 (corresponding to the structure of the claims) of the tunnel 10 has a plurality of block rows formed by a large number of blocks 14 made of bricks, concrete blocks, stones, or the like. 16A and 16B are laminated via a joint 18. In FIG. 1 and FIG. 2, only two block columns are drawn for convenience of explanation.
Specifically, a wall surface 22 (corresponding to the surface of the structure of the claims) defining the internal space 20 of the tunnel 10 is formed by the first block row 16A, and the second block row 16B is the first block row 16B. The block row 16A is provided outside via a joint 18.
In the wall portion 12 of the tunnel 10 configured in this way, cracks 24 may occur along the joints 18 interposed between the block rows 16A and 16B due to a decrease in adhesion due to secular change or an external force.

Next, the crack detection method of a present Example is demonstrated.
First, as shown in FIG. 4 and FIG. 5 (A), a hammer drill is provided so as to penetrate the predicted crack location 25 from the direction intersecting the crack direction in the crack location 25 predicted in the wall portion 12. 2 or the like is used to drill the hole 26. In this embodiment, the hole 26 is formed in a direction orthogonal to the wall surface 22.
The hole 26 is formed so as to penetrate the block 14 of the block row 16 </ b> A located on the wall surface 22 (front surface) of the wall portion 12 and reach the block 14 of the block row 16 </ b> B located inside the wall portion 12.
In the present embodiment, the inner diameter of the hole 26 is, for example, 5 mm or more and 20 mm or less.
In the present embodiment, the predicted cracked portion 25 is the joint 18.
For example, in the case of detecting a crack 24 in the joint 18 between the first block row and the second block row, as shown in FIG. 7 (A), between the first block row and the second block row, It forms so that the joint 18 may be penetrated.
In addition, when detecting the crack 24 of the joint 18 between the second block row and the third block row, as shown in FIG. 7B, between the second block row and the third block row. It forms so that the joint 18 may be penetrated.
It should be noted that the location of the wall 12 where the hole 26 is drilled may be the location of the wall 12 where the presence of cracks has been found by a conventionally known non-destructive inspection method, or such non-destructive inspection. It may be the location of the wall 12 where it has been found that cracks have not yet occurred by the method.
In this specification, the detection of cracks refers to the detection of new cracks that have not occurred so far, the detection of the progress or displacement of the original cracks, and the detection of other items related to cracks. Is included.

Next, as shown in FIG. 6, a metal pipe 28 is inserted into the back of the hole 26 and fixed to the back. In the present embodiment, the pipe 28 is fixed to the block 14 of the block row 16B located inside the wall portion 12.
The material of the pipe 28 is, for example, brass or aluminum.
For example, the outer diameter of the pipe 28 is fixed to be slightly smaller than the inner diameter of the hole 26, and the pipe 28 is driven into the inner part of the hole 26 for fitting. Alternatively, it may be performed by forming a gap between the outer peripheral surface of the pipe 28 and the inner peripheral surface of the hole 26 and filling the gap with an injection material such as mortar or an adhesive.

Next, as shown in FIG. 6, the shaft-shaped detection unit 30 is inserted into the inner periphery of the hole 26 and the tip thereof is inserted into the hole of the pipe 28 so as to be detachable.
And as shown in FIG. 7, the detection part 30 fixes the part located in the wall surface 22 of the hole 26 to the wall surface 22 so that a movement is impossible.
The outer diameter of the detection unit 30 is smaller than the inner diameter of the hole 26, and the detection unit 30 and the pipe 28 are configured to be movable relative to the axial direction of the detection unit 30. .
Further, the fixing hole 35 of the detection unit 30 is fixed to the wall surface 22 by inserting a fixing jig 35 at a position where the detection unit 30 is located on the wall surface 22 of the hole 26 as shown in FIG. This is performed by fixing the detection unit 30 and the wall surface 22.

As shown in FIG. 9, the detection unit 30 includes a hollow shaft-shaped member 3001 (FIG. 8) formed from a nonmagnetic material, and is wound around the central axis of the shaft-shaped member 3001 inside the shaft-shaped member 3001. The detection circuit 32 connected to the coil 3002 is provided outside the hollow shaft-shaped member 3001.
The detection circuit 32 includes a drive circuit 3202 and a data generation circuit 3204.
As shown in FIGS. 10 and 11, the drive circuit 3202 applies a magnetic field from the coil 3002 to the pipe 28 by applying a rectangular wave pulse voltage VP to the coil 3002.
The voltage detection signal VS output from the coil 3002 is detected by a data generation circuit 3204 including a resistor R, a capacitor C, and a detection circuit 3204A as shown in FIG.
As shown in FIG. 11B, when the rectangular wave pulse voltage VP is supplied to the coil 3002, it is affected by the inductance of the coil 3002, and the voltage detection signal VS is less than the pulse voltage VP. It becomes a waveform. In FIG. 11B, a solid line indicates a waveform in a state where the coil 3002 is inserted over the entire area of the pipe 28, and a broken line indicates a waveform in a state where the coil 3002 is completely removed from the pipe 28.
The gradient of the waveform of the voltage detection signal VS is a change amount that changes due to the influence of the eddy current induced in the pipe 28 by the magnetic field, and the change amount is the position of the pipe 28 in the central axis direction of the coil 3002. It depends on. In other words, the amount of change varies according to the relative position along the drilling direction of the drilling hole 26 of the pipe 28 with respect to the detection unit 30, and includes the portion of the block 14 to which the wall surface 22 and the pipe 28 are fixed. It changes according to the relative displacement along the drilling direction of the other drilling hole 26.
As shown in FIG. 11B, the slope of the waveform of the voltage detection signal VS is required from the rise of the pulse voltage VP applied to the coil 3002 until the voltage detection signal VS reaches a predetermined threshold value V1. It can be expressed by time T (T1, T2).
Therefore, the amount of change that changes according to the relative position along the drilling direction of the drilling hole 26 of the pipe 28 with respect to the detection unit 30 can be expressed by the time T required to reach the predetermined threshold value V1. In this embodiment, the time T, that is, the amount of change is detected by the data generation circuit 3204. Based on the amount of change, the drilling of the hole 26 between the wall surface 22 and the portion of the block 14 to which the pipe 28 is fixed is performed. Measure the relative displacement along the direction.
Further, the data generation circuit 3206 outputs the relative displacement as relative displacement data composed of digital data, for example.
The relative displacement data output from the data generation circuit 3206 is collected and recorded using a conventionally known data logger 34, for example.
In addition, as the detection part 30, the pulse coders LP-15, LP-20, LP-40, etc. of Ribex Co., Ltd. can be used, for example.

According to the present embodiment, the crack 24 generated inside the tunnel 10 is detected by detecting the relative displacement along the drilling direction of the drilling hole 26 between the wall surface 22 and the portion of the block 14 to which the pipe 28 is fixed. , And the change in the cracks can be detected accurately and in real time.
In addition, the diameter of the hole 26 to be drilled in the wall portion 12 may be a dimension (for example, 5 mm or more and 20 mm or less) that allows insertion of the metal pipe 28 and the detection unit 30 inserted through the inner periphery of the pipe 28. Unlike the method of drilling a circular core as described above, damage to the structure can be reduced.
Therefore, by arranging the pipes 28 and the detection units 30 at many locations along the extending direction of the tunnel 10, it becomes possible to easily and accurately manage the cracks of the tunnel 10.
Further, when the detection unit 30 is fixed to the wall surface 22 by the fixing jig 35 so as to be immovable, it is necessary to provide the detection unit 30 for each hole 26, but the detection unit 30 is provided only during the detection of the crack 24. It may be inserted through the hole 26 and fixed to the wall surface 22 so as to be removable, and the detection unit 30 may be removed from the wall surface 22 when the detection is completed. If it does in this way, the crack 24 of the several places of the wall part 12 can be detected by the one detection part 30, and it becomes advantageous when reducing cost. In other words, unlike the case where a conventional sensor is embedded in a structure and the strain of the structure is measured, the detection unit 30 can be detached from the structure, and thus the measurement with one hole 26 is completed. Since the detection unit 30 can be removed and the detection unit 30 can be carried to another hole 26 and measurement can be performed, the number of the detection units 30 is small, which is advantageous in reducing the cost.
When the single detection unit 30 is detachably fixed to the plurality of hole holes 26 in this way, the attachment position of the detection unit 30 with respect to the wall surface 22 is recorded (predetermined), and the detection unit When attaching 30 to the wall surface 22, it is necessary to be able to reproduce the attachment position.
Further, the portion of the wall portion 12 where the hole 26 is drilled may be a portion where the presence of cracks has been found by a conventionally known nondestructive inspection method, or cracks may be generated by such a nondestructive inspection method. It may be a location that has been found to have not yet occurred. That is, by drilling the hole 26 in a portion of a healthy structure where no crack has occurred and measuring the relative displacement data by the detection unit 30, a crack that has not occurred until then has newly occurred. Of course, this may be detected.
Further, by observing the inside of the hole 26 when the hole 26 is drilled, it is possible to grasp the state of the crack 24, the thickness of the tunnel lining, the state of the back ground, etc. Of course, it is possible to grasp the material characteristics inside the structure (in this embodiment, the block 14 and the joint 18) by analyzing the drilling pieces obtained from the above.

Next, Example 2 will be described.
The second embodiment is a modification of the first embodiment. In the first embodiment, a plurality of block rows 16 </ b> A and 16 </ b> B in which the wall portion 12 is configured by a large number of blocks 14 are stacked via joints 18. On the other hand, in Example 2, the wall part 12 is the point comprised by laminating | stacking several concrete layers.
FIG. 12 is an explanatory view showing a state in which the detection unit is fixed to the hole drilled in the wall portion 12 in the second embodiment, and the same reference numerals are given to the same parts or members as those in the first embodiment. The description is omitted.
As shown in FIG. 12, the wall portion 12 of the tunnel 10 is configured by laminating a plurality of concrete layers 40 </ b> A and 40 </ b> B formed by concrete spraying via a boundary surface 42. In FIG. 12, only two concrete layers 40A and 40B are drawn for convenience of explanation.
Specifically, the wall surface 22 (corresponding to the surface of the structure of the claims) that defines the internal space 20 of the tunnel 10 is located on the surface of the first concrete layer 40A (the structure of the claims). The second concrete layer 40B (corresponding to the concrete portion located inside the structure of the claims) is provided outside the first concrete layer 40A via the boundary surface 42. It has been.
In the wall portion 12 of the tunnel 10 configured as described above, a crack 24 may be generated along the boundary surface 42 between the concrete layers 40A and 40B due to a decrease in adhesion force due to secular change or an external force.

In the second embodiment, the hammer drill 2 or the like is used so as to penetrate the predicted crack location 25 from the direction intersecting the direction of the crack at the predicted crack location 25 in the same procedure as in the first embodiment. The hole 26 is drilled. In this embodiment, the hole 26 is formed in a direction orthogonal to the wall surface 22.
The hole 26 is formed so as to penetrate the concrete layer 40 </ b> A located on the wall surface 22 (surface) of the wall portion 12 and reach the concrete layer 40 </ b> B located inside the wall portion 12.
For example, when detecting the crack 24 on the boundary surface 42 between the first concrete layer 40A and the second concrete layer 40B, the boundary surface 42 between the first concrete layer 40A and the second concrete layer 40B is penetrated. To be formed.
Next, in the same manner as in Example 1, a metal pipe 28 is inserted into the inner part of the hole 26 and fixed to the inner part, and a shaft-shaped detection unit 30 is inserted into the inner periphery of the hole 26 and the tip thereof is inserted. The detection portion 30 is inserted into the hole of the pipe 28, and the part positioned on the wall surface 22 of the hole hole 26 is fixed to the wall surface 22 so as not to move.
Detection of the crack 24 by the detection unit 30 and the detection circuit 32 is the same as in the first embodiment.
Also in the second embodiment, similarly to the first embodiment, the relative displacement along the drilling direction of the drilling hole 26 between the wall surface 22 and the portion of the concrete layer 40B to which the pipe 28 is fixed is continuously detected. Thus, it becomes possible to accurately grasp the change in the size of the crack 24 in real time.
In addition, when the structure is formed by, for example, spraying or placing concrete, the present invention is naturally applied regardless of whether or not there is the boundary surface 42 as in the second embodiment.

Next, Example 3 will be described.
The third embodiment differs from the first and second embodiments in that the relative displacement data output from the detection circuit 32 is collected and recorded by the data logger 34 in the first and second embodiments, whereas the third embodiment is different from the first and second embodiments. Relative displacement data output from one or a plurality of detection circuits 32 is collected and recorded in real time via a network.
FIG. 13 is an explanatory diagram illustrating an example of a data collection system that collects relative displacement data according to the third embodiment.
As shown in FIG. 13, the data collection system 100 includes a plurality of detection units 30 and detection circuits 32, a server 102, an interface 104, a personal computer 106, a mobile phone 108, a network 110, and the like.
A plurality of detection units 30 are arranged at a plurality of expected cracks in a plurality of tunnel structures, and a detection circuit 32 is connected to each detection unit 30.
The interface 104 supplies the relative displacement data output from each detection circuit 32 to the server 102 through a predetermined interface such as RS-232C or USB.

The server 102 stores the relative displacement data collected through the interface 104 in association with the name of the structure in which each detection unit 30 is installed and the installation location of the detection unit 30 to configure a database.
The personal computer 106 constitutes a terminal device that can be connected to the network 110, and accesses the server 102 via the network 110 including the public line and the Internet, browses the database of the server 102, or Configured to receive data from the database.
The mobile phone 108 also constitutes a terminal device that can be connected to the network 110, and, like the personal computer 106, a server via the network 110 including a wireless line for the mobile phone 108 and a network for the mobile phone 108. It is configured to access 102 and browse the database of the server 102 or receive data from the database.
The terminal device may be any device that can be connected to the network 110, and a PDA or other portable terminal can be used.

In addition, the server 102 may periodically collect the relative displacement data, or the personal computer 106 or the mobile phone 108 may request the server 102 via the network 110 and respond to the request. The server 102 may do this.
Further, instead of the personal computer 106 or the cellular phone 108 accessing the server 102, the server 102 may periodically distribute the data of the database to the personal computer 106 or the cellular phone 108 via the network 110.
As described above, the relative displacement data output from the plurality of detection units 30 and the detection circuit 32 provided at the plurality of expected cracks in the plurality of tunnel structures is collected and recorded in real time via the network. By doing so, it becomes possible to perform the crack management of the plurality of tunnels 10 easily and accurately.

In addition, although the Example demonstrated the case where a structure was the wall part 12 of the tunnel 10, this invention is not limited to the tunnel 10, For example, many block row | line | columns were laminated | stacked through the joint. Of course, it is also applied to the detection of cracks in the handrail or column wall of a bridge.
In addition, in the embodiment, as a place where cracks are detected, a case where a large number of block rows are joint portions between blocks in a structure laminated through joints, or concrete is sprayed or beaten. Although the case inside the structure comprised by being provided was demonstrated, respectively, the location which detects a crack is not limited to this.
That is, when the structure is a block stack in which a large number of block rows are stacked via joints, in addition to the block-to-block interlayer location as described in Example 1, as the location to detect cracks, For example, between the block and the surface protection layer, or between the block and the repair / reinforcement work (originally a block-stacked structure, but the layer applied to the brick surface for the purpose of repair, reinforcement or surface protection) Examples include places.
Further, when the structure is constructed by spraying or placing concrete, as a part for detecting cracks, in addition to the part inside the integrated concrete as described in Example 2, for example, spraying Or between the concrete part composed of casting and this concrete part and another concrete layer applied later, or the concrete part constructed by spraying or casting and this concrete part Examples include surface protection work that has been applied later, and interlaminar locations with layers by repair and reinforcement methods.
According to the present invention, for example, it is possible to perform both detection of a new crack and detection of the progress of an original crack, for example, for each of the above-described locations.
In the embodiment, the detection unit 30 includes a coil 3002 and applies a pulse voltage to the coil 3002 to apply a magnetic field from the coil 3002 to the pipe 28, and the influence of eddy currents induced in the pipe 28 by this magnetic field. The case where the gradient of the waveform of the voltage detection signal obtained from the coil 3002 that changes in response to the change is detected as the amount of change has been described.
However, the amount of change is not limited to the gradient of the waveform of the voltage detection signal obtained from the coil 3002, and changes according to the relative position along the drilling direction of the drilling hole 26 of the pipe 28 with respect to the detection unit 30. The change amount is not limited to the principle of the detection unit 30 and the detection circuit 32 described in the embodiment, and various conventionally known methods and principles can be adopted.

It is explanatory drawing of the wall part structure of the tunnel which is a structure in Example 1. FIG. It is a principal part enlarged view of FIG. FIG. 3 is a sectional view taken along line AA in FIG. 2. It is explanatory drawing which shows the process of drilling a hole in a structure. (A), (B) is explanatory drawing of the drilling hole formed in the structure. It is explanatory drawing which shows the state which inserted and fixed the pipe in the drilling hole formed in the structure. It is explanatory drawing which shows the state which fixed the detection part to the drilling hole. It is explanatory drawing of the detection operation by a detection part. It is explanatory drawing which shows the structure of a detection part and a detection circuit. It is a circuit diagram which shows a part of detection circuit. It is a signal waveform diagram explaining operation | movement of a detection part and a detection circuit. It is explanatory drawing which shows the state by which the detection part was fixed to the hole drilled in the wall part 12 in Example 2. FIG. It is explanatory drawing which shows an example of the data collection system which collects the relative displacement data in Example 3.

Explanation of symbols

10 ... Tunnel 12 ... Wall 14 ... Block 18 ... Joint 22 ... Wall 24 ... Crack 26 ... Drilling hole 28 ... Pipe 30 ... Detection part.

Claims (11)

A method for detecting cracks inside a structure,
Drilling a hole to penetrate the predicted cracked part from the direction intersecting the direction of the crack in the predicted cracked part, fixing a metal pipe at the back of the hole, Insert the shaft-shaped detection part into the inner periphery of the hole and insert the tip into the hole of the pipe, and fix the part of the detection part located on the surface of the structure where the hole is opened. Aside,
The amount of change that changes according to the relative position along the drilling direction of the drilling hole of the pipe with respect to the detection unit is detected via the detection unit,
By measuring the relative displacement along the drilling direction of the drilling hole between the surface of the structure and the portion of the structure to which the metal pipe is fixed from the amount of change detected by the detection unit. Detecting cracks,
A method for detecting cracks in a structure characterized by the above.   The detection unit includes a coil, and applies a pulse voltage to the coil to apply a magnetic field from the coil to the pipe, and the coil changes under the influence of an eddy current induced in the pipe by the magnetic field. 2. The method for detecting cracks in a structure according to claim 1, wherein a gradient of a waveform of a voltage detection signal obtained from the above is detected as the amount of change.   The detection unit includes a hollow shaft-shaped member formed of a non-magnetic material, and a coil wound around the center axis of the shaft-shaped member inside the shaft-shaped member, and a pulse voltage is applied to the coil. Is applied to the pipe from the coil, and the gradient of the waveform of the voltage detection signal obtained from the coil that changes under the influence of the eddy current induced in the pipe by the magnetic field is changed. 2. The method for detecting cracks in a structure according to claim 1, wherein the detection is performed by a detection circuit connected to the coil outside the hole.   2. The method for detecting cracks in a structure according to claim 1, wherein the hole is formed in a direction perpendicular to the surface of the structure.   The structure is a tunnel wall portion or a bridge railing or a column wall portion in which a large number of block rows are stacked via joints, and the drilled holes are blocks of blocks arranged on the surface of the structure. 2. The block is formed so as to penetrate to a block row block located inside the structure, and the pipe is fixed to a block row block located inside the structure. A method for detecting cracks in the structure described.   The structure is made of concrete, and the hole is formed so as to penetrate a concrete portion located on the surface of the structure to reach a concrete portion located inside the structure, and the pipe 2. The method for detecting cracks inside a structure according to claim 1, wherein the crack is fixed to a concrete portion located inside the structure.   8. The method for detecting cracks in a structure according to claim 7, wherein the structure is formed by spraying or placing concrete.   9. The internal crack of the structure according to any one of claims 1 to 8, wherein the detection portion is fixed to a surface of the structure body in which the hole is opened. Detection method.   The relative displacement is measured from the amount of change detected by the detection unit, data of the measured relative displacement is collected in a server, and the server and the terminal device are connected via a network. 2. The method for detecting cracks inside a structure according to claim 1, wherein the relative displacement data collected by the server is accessed from the terminal device via the network.   The relative displacement is measured from the amount of change detected by the detection unit, data of the measured relative displacement is collected in a server, and the server and the terminal device are connected via a network. 2. The method for detecting cracks in a structure according to claim 1, wherein the relative displacement data collected by the server is distributed from the server to the terminal device via the network.   The detection of the crack is to newly detect a crack that has not occurred until then, or to detect the progress or displacement of the original crack. How to detect cracks.

Images