JPS61128135A - Method for detecting contact of concrete reinforcement and piping - Google Patents

Abstract

PURPOSE:To detect the contact of piping and reinforcement, by flowing a signal current between the embedded piping embedded in a concrete wall so as to pierce therethrough and the reinforcement of the concrete wall and moving differentially connected search coils to detect the difference between the intensities of electromagnetic fields. CONSTITUTION:In such a state that a signal current (i) is flowed between the embedded piping 1 such as the gas pipe embedded in a concrete wall 4 so as to pierce therethrough and the concrete reinforcement 2 embedded in the concrete wall 4 by a transmitter 5, two search coils 7, 7 connected to a differential coil structure in a state mutually assembled thereto so as to leave a definite distance L therebetween are moved along the surface of the concrete wall 4 and the outer surface of the piping 1. When the piping 1 and the reinforcement 2 are connected at the peripheral direction area of the piping 1, the difference between the intensities of electromagnetic fields due to the current (i) is detected by the coils 7, 7. By this method, the presence and position of the contact of the piping and the reinforcement can be accurately detected.

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 that is detected from outside the concrete wall. More specifically, it is based on the form of electromagnetic field formed by the current flowing through concrete reinforcing bars and piping. The purpose of this technology is to accurately detect physical contact and the location of contact.

[Conventional technology]

Concrete reinforcing bars in concrete walls (below).

(simply referred to as reinforcing bars) are assembled in a grid pattern, so
Buried pipes such as gas pipes that penetrate through this concrete wall and are buried underground may come into electrical contact with the above-mentioned reinforcing bars.

When the reinforcing bars and piping come into electrical contact in this way, C/
S-based corrosion will occur in the underground portion of the piping.

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 (
Since the water flows in at a ratio of about 1:10 to 15), 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.

Problems to be solved by the invention C] As a means of improving the electrical insulation between the piping and the reinforcing bars, firstly, cutting the piping, secondly, chiseling the entire circumference of the concrete wall, and thirdly, removing the existing There are methods such as cutting the pipe and inserting the desired pipe into the existing pipe.

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 the Problems] The present invention has been devised to be effective in implementing the second means efficiently, and the present invention has been devised to efficiently implement the second means. This makes it possible to accurately detect the presence or absence of contact between the pipe and the reinforcing bar, as well as the position of the contact, based on the strength relationship.

Hereinafter, a method for detecting contact between concrete reinforcing bars and piping according to the present invention will be described 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 are moved to detect the difference in the strength of the electromagnetic field 6 generated by the signal current i, and At circumferential locations of the pipe 1 where there is a large difference in the strength of the field 6,
It is designed to detect that the pipe 1 and the reinforcing bar 2 are in contact with each other.

[Function and Examples]

That is, as shown in Fig. 1, when both terminals of two transmitters 5 are connected to pipe 1 and reinforcing bar 2 and a signal current i is passed, if pipe 1 and reinforcing bar 2 are in contact with each other, one signal will be emitted. Both terminals of the device 5 are short-circuited by the pipe 1 and the reinforcing bar 2, and a large signal current is generated! will flow.

This signal current i flows through the reinforcing bar 2 in complicated ways as shown in FIG. 1, but is concentrated at the contact point 3 with the pipe 1,
In other words, it concentrates on the reinforcing bars 2 that are in contact with the pipe 1 and then flows into the pipe 1.

Therefore, as shown in FIGS. 2, 3, and 4, the electromagnetic field 6 formed by the signal types 'e and j is in contact with the pipe 1 and the signal current i
This will occur to a large extent in the reinforcing bars 2, where the flow is concentrated.

The electromagnetic field 6 is distributed 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, the strength e of the electromagnetic field 6 at each position on the circumferential surface of the pipe 1 is as shown in Fig. 5, and shows a large value at the circumferential surface location where the contact point 3 is located. become.

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 The difference between the strength of the electromagnetic field 6 at the circumferential surface of the pipe 1 and the strength of the electromagnetic field 6 at other circumferential parts is not large, and therefore the strength of the electromagnetic field 6 cannot be directly detected. By detecting the contact point 3, it is not always possible to accurately and reliably detect the circumferential position of the contact point 3.

Therefore, as shown in FIG. 7, two search coils 7.7 are provided with a small distance apart, and these two search coils 7.7 are connected to a differential coil structure to extend the coils along the circumferential surface of the pipe 1. If the difference e in the strength of the electromagnetic field 6 at two locations is detected, the electromagnetic field 6 along the circumferential surface of the pipe 1 will be detected.
The change in the strength difference e' is as shown in Fig. 6, and the value at the circumferential surface of the pipe 1 corresponding to the contact point 3 becomes extremely thick. can be detected reliably and accurately.

In this way, the method of detecting contact between reinforcing bars 2 and piping 1 according to the present invention detects contact between reinforcing bars 2 and piping 1 by detecting contact along the surface of concrete wall 4 and the circumferential surface of piping 1 with signal current i flowing between reinforcing bars 2 and piping 1. By slidingly moving the two search coils 7, it is possible to determine the presence or absence of the contact point 3 and the presence or absence of the contact point 3 in the circumferential direction of the pipe 1, based on the strength difference e' of the electromagnetic field 6 along the circumferential surface of the pipe 1. The location can be detected accurately and 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 piping 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 piping and reinforcing bars, as well as its position. WI'R can remove the electrical contact between the pipe and the reinforcing steel by chiseling the concrete wall facing the detected contact point or by drilling a hole with a mini-dymo drill, etc., thereby making it possible to apply cathodic protection to the pipe. This makes it easier, and also eliminates the problem of C/S macrocell flattened 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 two methods of the present invention are carried out. FIG. 2 is a 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. FIG. 3 is a partial vertical sectional view of FIG. 2. FIG. 4 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. FIG. 7 is a diagram showing an example of the configuration 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, iH signal current. Applicant Japan Anti-Corrosion Industry NPla Co., Ltd./'P7G

Claims (1)

[Claims] Connected to a differential coil structure along the concrete wall surface and the outer circumferential surface of the pipe while passing a signal current between the buried pipe penetrated through the concrete wall and the reinforcing steel of the concrete wall. Two search coils assembled to each other at a constant interval are moved to detect the difference in electromagnetic field strength caused by the signal current, and the pipe and reinforcing steel are connected to the pipe at a circumferential location of the pipe where the difference in electromagnetic field strength is large. A contact detection method between concrete reinforcing bars and piping to detect contact.