JPH043818B2 - - Google Patents

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention provides electrical contact between concrete reinforcing bars buried in a concrete wall and buried piping that penetrates through the concrete wall and is buried underground. This relates to a method for detecting contact between concrete reinforcing bars and piping from outside a concrete wall, and more specifically, it detects contact between concrete reinforcing bars and piping by using the form of electromagnetic field formed by current flowing through concrete reinforcing bars and piping. The purpose of this is to accurately detect electrical contacts and their contact points.

[Conventional technology]

Concrete reinforcing bars in concrete walls (hereinafter referred to as
(simply referred to as reinforcing bars) are assembled in a lattice pattern, so there may be electrical contact between the above-mentioned reinforcing bars and buried pipes such as gas pipes that penetrate through the concrete wall and are buried underground. .

If the reinforcing steel and the pipe come into electrical contact in this way, corrosion of the C/S system will occur in the underground portion of the pipe.

In addition, even if cathodic protection is applied to the underground part of the piping with electrical contact between the reinforcing steel and the piping, the corrosion protection current is inversely proportional to the grounding resistance of the piping and the reinforcing steel (1:10). 15), so a sufficient effect cannot be obtained.

Therefore, there is a need to improve the electrical insulation between the pipe and the reinforcing steel where the pipe penetrates the concrete wall.

[Problem that the invention seeks to solve]

To improve the electrical insulation between the pipe and the reinforcing steel, the first step is to cut the pipe, the second is to chisel the entire circumference of the concrete wall, and the third is to cut the existing pipe and install it inside the existing pipe. There are methods such as inserting the desired piping.

The first and third methods require cutting the piping, and completely new piping must be installed after the improvement.

On the other hand, with the second method, if the contact position between the reinforcing steel and the piping can be accurately detected, chipping and drilling of the concrete wall will be minimized, and when implementing this method, there will be no damage to the concrete wall. can be kept to a minimum.

[Means for solving problems]

The present invention was devised to be effective in implementing this second means efficiently, and is based on the relationship between the magnitude of the magnetic field strength of the electromagnetic field generated around the passage of current. This makes it possible to accurately detect the presence or absence of contact with the object and the location of the contact.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A method for detecting contact between concrete reinforcing bars and piping according to the present invention will be described below with reference to drawings showing an embodiment of the present invention.

The method of detecting contact between concrete reinforcing bars and pipes according to the present invention is characterized in that a signal current is generated between a buried pipe 1 such as a gas pipe penetrated through a concrete wall 4 and a concrete reinforcing bar 2 buried in the concrete wall 4. i along the surface of the concrete wall 4 and the outer peripheral surface of the pipe 1,
Two search coils 7, 7 connected to a differential coil structure and assembled to each other at a certain distance L are moved to detect the difference in the strength of the electromagnetic field 6 generated by the signal current i, and to detect this electromagnetic field. It is designed to detect that the pipe 1 is in contact with a reinforcing bar 2 at a circumferential location of the pipe 1 where there is a large difference in the strength of the field 6.

[Function and Examples]

That is, as shown in Fig. 1, when both terminals of the transmitter 5 are connected to the pipe 1 and the reinforcing bar 2 and a signal current i is passed, if the pipe 1 and the reinforcing bar 2 are in contact, the signal will not be transmitted. Both terminals of the device 5 are short-circuited by the pipe 1 and the reinforcing bar 2, and a large signal current i flows therethrough.

This signal current i flows through the reinforcing bar 2 in a complicated manner as shown in FIG. After that, it flows into pipe 1.

Therefore, as shown in FIGS. 2, 3, and 4, the electromagnetic field 6 formed by the signal current i is in contact with the pipe 1, so that the signal current i is This will occur largely in the reinforcing bars 2 that flow in a concentrated manner.

This electromagnetic field 6 distribution form is applied to the pipe 1 along the surface of the concrete wall 4 that is a short distance away from the reinforcing bars 2 that are in contact with the pipe 1, and along the circumferential surface of the pipe 1.
When detected by a search coil as the strength of the electromagnetic field 6 at each position on the circumferential surface of the pipe 1, the strength e of the electromagnetic field 6 at each position on the circumferential surface of the pipe 1 is as shown in FIG. It shows a large value at the circumferential surface where is located.

In this way, the circumferential position of the contact point 3 can be detected by directly detecting the strength of the electromagnetic field 6 along the circumferential surface of the pipe 1, but in reality, the position of the contact point 3 is Electromagnetic field 6 at the peripheral surface position of pipe 1
The difference between the strength of the electromagnetic field 6 and the strength of the electromagnetic field 6 at other peripheral parts is not large. Therefore, if the strength of the electromagnetic field 6 is directly detected to detect the contact point 3, it is difficult to detect the contact point 3. It is not always possible to detect the circumferential position accurately and reliably.

Therefore, as shown in FIG. 7, two search coils 7, 7 are provided with a small distance L apart, and these two search coils 7, 7 are connected in a differential coil structure to extend along the circumferential surface of the pipe 1. When the difference e' in the strength of the electromagnetic field 6 at two locations is detected, the change in the difference e' in the strength of the electromagnetic field 6 along the circumferential surface of the pipe 1 becomes as shown in Fig. 6. , the value at the circumferential surface of the pipe 1 corresponding to the contact point 3 becomes extremely large, thereby making it possible to detect the circumferential surface of the contact point 3 reliably and accurately.

As described above, the method of detecting contact between the reinforcing bars 2 and the pipe 1 according to the present invention detects contact along the surface of the concrete wall 4 and the circumferential surface of the pipe 1 while the signal current i is flowing between the reinforcing bars 2 and the pipe 1. Two search coils 7
By sliding this, the presence or absence of the contact point 3 and the position of this contact point 3 in the circumferential direction of the pipe 1 can be accurately determined based on the strength difference e' of the electromagnetic field 6 along the circumferential surface of the pipe 1. And it can be detected reliably.

Therefore, it is possible to know whether there is contact between the pipe 1 and the reinforcing bar 2 without destroying the concrete wall 4.

〔Effect of the invention〕

As is clear from the above description, the method for detecting contact between pipes and reinforcing bars according to the present invention is easy to operate, and can reliably and accurately detect the presence or absence of contact between pipes and reinforcing bars, as well as its position. It is easy to remove the electrical contact between the pipe and the reinforcing steel by drilling the concrete wall facing the detected contact point or by drilling a hole with a mini-dymo drill, etc., which makes it possible to apply cathodic protection to the pipe. It is easy to use and also eliminates C/S macro cell corrosion batteries.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram showing an example of the distribution form of signal current in piping and reinforcing bars when the method of the present invention is implemented. FIG. 2 is an explanatory perspective view of a main part showing the form of an electromagnetic field generated around piping and reinforcing bars by the signal current shown in FIG. 1. Third
The figure is a partial vertical sectional view of FIG. 2. Figure 4 shows
FIG. 3 is a partial front view of FIG. 2; FIG. 5 is a diagram showing an example of changes in the intensity of the electromagnetic field along the circumferential surface of the pipe. FIG. 6 is a diagram of the electromagnetic field strength difference of the example shown in FIG. 5 along the circumference of the pipe. Figure 7 shows
It is a figure showing an example of composition of a search coil. Explanation of symbols, 1... Piping, 2... Rebar, 3...
Contact point, 4... Concrete wall, 5... Transmitter,
6...Electromagnetic field, 7...Search coil, i...Signal current.

Claims (1)

[Claims] 1. With a signal current flowing between the buried pipe that has penetrated through the concrete wall and the reinforcing steel of the concrete wall, the pipe is connected to a differential coil structure along the surface of the concrete wall and the outer peripheral surface of the pipe. The difference in electromagnetic field strength caused by the signal current is detected by moving two search coils assembled to each other at a constant interval, and the difference in electromagnetic field strength between the piping and the piping is detected at a circumferential location of the piping where the difference in electromagnetic field strength is large. A method for detecting contact between concrete reinforcing bars and piping to detect if they are in contact with reinforcing bars.