JP2016008868A - Pipe locating method and pipe locating system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pipe locating method capable of highly accurately measuring earth covering of a pipe material.SOLUTION: A pipe locating method which measures earth covering Z of a pipe material T formed of metal and embedded in the ground includes: supplying AC current between a first position P1 and a second position P2 provided with an interval in a longitudinal direction X of the pipe material; changing a value of the AC current by using a variable resistor 15 that can continuously change a resistance value, and setting the value of the AC current to a fixed value I which is set in advance; measuring a value E of induction electromotive force generated in a coil device 25 installed on the ground, from a change in magnetic field caused by the AC current; and calculating the earth covering Z from the formula (1): (1) Z=(K×I)/E-L-D/2, where L is defined as a distance from the ground surface to the center of the coil device, D as an outer diameter of the pipe material, and K as a constant.

Description

  The present invention relates to a pipe locating method and a pipe locating system.

Conventionally, a pipe locating method has been used to examine a state in which a pipe formed of metal is buried in the ground.
As this type of pipe locating method, for example, the one described in Patent Document 1 is known.

A pipe locating system for implementing a pipe locating method includes two exploration coils (coil devices) for capturing a generated magnetic field, signal output means for outputting the captured magnetic field as a detection signal, and processing the output signal And the exploration device main body displaying the result on the screen.
The two search coils are arranged in parallel in the vertical direction with an interval of 2 l.
In the pipe locating method of Patent Document 1, as shown in FIG. 7, there is a method generally called an energization method in which one end of the transmitter 100 is connected to the pipe material T buried in the ground, that is, the soil G1. Used.

It is assumed that a sufficiently long metal tube (tube material) is embedded in a straight line at a position at a vertical distance y from the intermediate position between the two search coils, and a current Isin (ωt) flows through the metal tube. This current is supplied from the ground electrode of the transmitter 100 to the metal tube.
When two exploration coils are arranged in the vicinity of the metal tube in parallel with the ground surface, the electromotive forces el and eh generated in the exploration coils are given by the following equations.
el = k (1 / y−1) Iωsin (ωt) (1)
eh = k (1 / y + 1) Iωsin (ωt) (2)
Here, k is a constant determined by the search coil.

Solving equations (1) and (2) as simultaneous equations,
y = ((el + eh) / (el-eh)) l (3)
It becomes.
From the equation (3), if the electromotive forces el and eh generated in the exploration coil are measured, the embedding depth y of the metal tube can be measured. The earth covering can be obtained by subtracting a value half of the outer diameter of the metal tube from the embedment depth y.

As a pipe locating method, a dielectric method or a two-point method is known in addition to the energization method described above.
As shown in FIG. 8, the dielectric method is a method in which an oscillator 101 is installed on the ground on the tube material T, and an induced current flows through the tube material T by the transmitter 101 generating a magnetic field. The two-point method is a complementary method in which a transmitter 102 is connected between two points of the pipe T as shown in FIG. 9, and a closed circuit is formed by the pipe T and the transmitter 102 so that a current flows through the pipe T.

Utility Model Registration No. 3112490

However, in the method described in Patent Document 1, since the exploration coils interfere with each other, the earth covering cannot be measured with high accuracy.
In the energization method, the measurement error is large when the strength of the signal current (inductive magnetic field strength) varies depending on the measurement point by the coil device, or when the tube T is in contact with another buried object other than the tube T. There is a problem of becoming. The two-point method is mainly applied to a small scale (a length of about several meters to several tens of meters) such as a supply pipe.
In the dielectric method, when the same problem as that of the energization method occurs, the accuracy decreases due to the small signal current.

  The present invention has been made in view of such problems, and an object of the present invention is to provide a pipe locating method and a pipe locating system capable of measuring the covering of a pipe material with high accuracy.

In order to solve the above problems, the present invention proposes the following means.
The pipe locating method of the present invention is a pipe locating method for measuring the earth covering of a pipe material formed of metal and embedded in the ground, wherein the first position and the second position are separated from each other in the longitudinal direction of the pipe material. An alternating current is supplied between the two and a variable resistor capable of continuously changing the resistance value is used to change the alternating current value, and the alternating current value to be measured is set to a predetermined value. The induced electromotive force E generated in the coil device arranged on the ground due to the change of the magnetic field due to the alternating current is measured, the distance from the ground surface to the center of the coil device is L, and the outer diameter of the pipe is When D and K are constants, the earth covering Z is obtained from the equation (4).
Z = (K × I) / E−L−D / 2 (4)

  The pipe locating system of the present invention is a pipe locating system for measuring a covering of a pipe formed of metal and embedded in the ground, wherein the pipe locating system is separated from each other in the longitudinal direction of the pipe. A current supply device for supplying an alternating current between two positions; a variable resistor capable of continuously changing a resistance value; and a current for measuring the value of the alternating current. It is provided with a measuring device, a coil device which is arranged on the ground and generates an induced electromotive force by a change in a magnetic field due to the alternating current, and a voltage measuring device which measures the induced electromotive force generated in the coil device. .

According to the present invention, the current supply device generally has a resolution and cannot output an alternating current value as a continuous value. The resistance value between the first position and the second position of the pipe material varies depending on the length between the two positions, the material of the pipe material, and the like. For this reason, it is not possible to flow an alternating current having a predetermined value such as 1.00 A (ampere) determined between the first position and the second position of the pipe material regardless of the pipe material. Therefore, for example, by continuously changing the resistance value of the variable resistor from a state where the value of the alternating current is 0.99 A, the value of the alternating current flowing through the tube can be set to a predetermined value.
When the value of the alternating current flowing through the pipe material at each measurement becomes a predetermined value, there is no error in the value of the alternating current due to the measurement, and the alternating current value I in equation (4) becomes constant.

In the above pipe locating method, when changing the value of the alternating current using the variable resistor, it is more preferable to change the value of the alternating current while reducing the resistance value.
Further, in the pipe locating method, the value of the alternating current is measured by a current measuring device, and the predetermined value is not less than a median value and not more than an upper limit value in a measurement range of the current measuring device. More preferred.
According to the present invention, the current measuring device generally has a measurement error of 1.0 grade or 0.5 grade based on Japanese Industrial Standard. That is, the current measuring device is allowed to have a measurement error of ± 1.0% and ± 0.5% of the measurement range. Since the value of the alternating current flowing through the pipe material with respect to the measurement error of the current measuring device is increased, the error in the value of the alternating current is reduced.

  In the present invention, according to the pipe locating method according to claim 1 and the pipe locating system according to claim 4, the value I of the alternating current in equation (4) is constant, and the measurement of the covering of the pipe material is performed. Stable covering can be measured with high accuracy.

According to the pipe locating method according to claim 2, it is possible to prevent an excessive alternating current from flowing through the current supply device and the current measurement device, and to prevent damage to a circuit and the like in the current supply device and the current measurement device. be able to.
According to the pipe locating method of the third aspect, the covering of the pipe material can be measured with higher accuracy.

It is a block diagram of the pipe locating system of one embodiment of the present invention. It is a flowchart which shows the pipe locating method of this embodiment. It is a figure explaining the magnetic field which generate | occur | produces around the pipe material in the same pipe locating method. It is a figure explaining the state which moves a sensor coil with respect to a pipe material with the pipe locating method. It is a figure which shows the magnitude | size of the induced electromotive force with respect to the position of a sensor coil. It is a figure explaining the combination of the structure of the same pipe locating system. It is a figure explaining the pipe locating method by the conventional electricity supply method. It is a figure explaining the pipe locating method by the conventional dielectric method. It is a figure explaining the pipe locating method by the conventional two-point method.

Hereinafter, an embodiment of a pipe locating system according to the present invention will be described with reference to FIGS. 1 to 6.
As shown in FIG. 1, the pipe locating system 1 of this embodiment measures the earth covering Z (m) of the pipe material T embedded in the ground, that is, in the soil G1.
The pipe locating system 1 includes a current supply device 10 that supplies an alternating current to the pipe T, a variable resistor 15 that can continuously change a resistance value (electric resistance value), and an AC current that flows through the pipe T. An ammeter (current measuring device) 20 for measuring the value, a sensor coil (coil device) 25 arranged on the ground, a voltmeter (voltage measuring device) 30 for measuring the value of the induced electromotive force generated in the sensor coil 25, and It has.

In this example, the current supply device 10 and the ammeter 20 are built in the transmitter 2, and the voltmeter 30 is built in the signal processor 3. However, you may comprise so that the electric current supply apparatus 10 and the ammeter 20 may be connected in series with the lead wire 35 mentioned later. You may comprise so that the voltmeter 30 may be directly connected to the lead wire 36 mentioned later.
The tube material T is made of a metal such as steel. The outer diameter of the tube material T is set to D (m).
The tubular material T is provided with tubular lifting portions T1 and T2 with an interval in the longitudinal direction X of the tubular material T. The pulling portions T1 and T2 can be formed of the same material as the tube material T. In addition, the shape of raising part T1, T2 is not specifically limited, Tubular or linear may be sufficient.
A lower end portion of the pulling portion T1 is connected to the first position P1 of the pipe material T. A lower end portion of the lifting portion T2 is connected to the second position P2 of the pipe material T. The upper ends of the lifting portions T1 and T2 reach the ground surface G2.

The end portions of the lead wires 35 are connected to the upper end portion of the pulling portion T1 and the upper end portion of the pulling portion T2, respectively.
On the lead wire 35, the aforementioned variable resistor 15 and the transmitter 2 are connected in series.
The current supply device 10 can apply a potential difference due to an AC voltage from 0 V to 60 V, for example, in increments of 0.1 V between portions of the lead wire 35 connected to the transmitter 2. That is, the resolution of the voltage output of the current supply device 10 is 0.1V.
The current supply device 10 supplies an alternating current between the first position P1 and the second position P2 of the tube material T via the pulling portions T1 and T2 by applying a potential difference to the lead wire 35.

The variable resistor 15 has a known configuration. The variable resistor 15 rotates the dial portion 15b with respect to the main body 15a, for example, so that the resistance value between the contacts (not shown) provided on the main body 15a becomes a first resistance value and a first resistance value larger than the first resistance value. It can be continuously changed between two resistance values. For example, the first resistance value is 0Ω (ohms) and the second resistance value is 10Ω.
The lead wires 35 are connected to the contacts, respectively.
The value of the alternating current flowing through the tube material T can be changed by operating the dial portion 15b to change the resistance value of the variable resistor 15.

The ammeter 20 has a display unit (not shown), for example. The resolution (measurement accuracy) of the ammeter 20 is, for example, 0.01 A (10 mA (milliampere)), and the display unit of the ammeter 20 displays the value of the alternating current measured by the ammeter 20 in increments of 0.01 A. The The ammeter 20 has a measurement error such as 0.5 grade based on Japanese Industrial Standard. The measurement range of the value of the alternating current by the ammeter 20 is, for example, 0 A or more and 1.50 A or less. The value of the alternating current below is described in consideration of significant figures based on the resolution of the ammeter 20.
The application range of the AC voltage by these current supply devices 10, the first and second resistance values of the variable resistor 15, and the measurement range of the ammeter 20 are appropriately set according to the material and length of the tube T, It is not limited to these ranges.

The sensor coil 25 is obtained by winding a coil wire in a spiral shape. The sensor coil 25 generates an induced electromotive force between both ends of the strand due to a change in magnetic field due to an alternating current flowing through the tube T.
The voltmeter 30 has a known configuration. The sensor coil 25 and the signal processor 3 are connected by a lead wire 36.

Next, the pipe locating method of this embodiment using the pipe locating system 1 configured as described above will be described. FIG. 2 is a flowchart showing the pipe locating method of this embodiment. Hereinafter, the case where the ground surface G2 is parallel to the horizontal plane will be described.
Before carrying out this pipe locating method, the pipe material T is embedded in the soil G1 in advance in a laboratory or the like, and the soil covering Z is already known, and the pipe locating system 1 is handled by the method described later. A constant K in equation (5) described later is obtained. Below, it measures using each structure of the pipe locating system 1 when the constant K is calculated | required previously.

It is preferable to operate the dial portion 15b of the variable resistor 15 so that the resistance value of the variable resistor 15 is set to the second resistance value having a large value.
The value (predetermined value) of the alternating current that flows through the tube T after adjustment by the variable resistor 15 is set in advance to, for example, 1.00 A. This value is a median value (average value of lower limit value and upper limit value, 0.75 A) or more and an upper limit value (1.50 A) or less in the measurement range of the ammeter 20 that is, for example, 0 A or more and 1.50 A or less. Preferably there is.

First, in step S10, the current supply device 10 of the transmitter 2 is operated, and an alternating current is generated between the first position P1 and the second position P2 of the pipe T through the lead wire 35 and the pulling portions T1 and T2. Supply. Specifically, the voltage applied between both positions P1 and P2 of the tube material T is gradually increased from 0V in increments of 0.1V, such as 0.1V, 0.2V,. Along with this, the value of the alternating current flowing through the tube material T increases stepwise.
At this time, as shown in FIG. 3, the magnetic field F due to the alternating current is generated coaxially with the axis C <b> 1 of the tube T.

In step S12, the value I (A) of the alternating current flowing through the tube T measured by the ammeter 20 is changed using the variable resistor 15, and the value of the alternating current is set to the above-described 1.00A. Since the resistance value of the variable resistor 15 can be continuously changed, the value I of the alternating current can be reliably set to 1.00 A by finely adjusting the dial portion 15b.
At this time, it is preferable to change the value of the alternating current while operating the dial portion 15b of the variable resistor 15 to reduce the resistance value of the variable resistor 15 from the second resistance value. The value of the alternating current flowing through the tube T, that is, the current supply device 10 and the ammeter 20 gradually increases.

  As shown in FIG. 3, the sensor coil 25 is disposed on the ground (above the ground surface G2) so that the axis C2 of the sensor coil 25 is parallel to the horizontal plane. At this time, let L be the distance in the vertical direction from the ground surface G2 to the center of the sensor coil 25. In the following, the sensor coil 25 is moved in parallel with the ground surface G2 while maintaining this distance L.

In step S <b> 14, the voltmeter 30 measures the value E of the induced electromotive force generated in the sensor coil 25 due to the change of the magnetic field due to the alternating current flowing through the tube T.
Since the magnetic field F is formed along the axis C1 of the tube T, the sensor coil 25 is arranged so that the axis C1 of the tube T and the axis C2 of the sensor coil 25 are parallel, and the sensor coil 25 is moved in the direction of the axis C1. Even if it is moved, the value E of the induced electromotive force generated in the sensor coil 25 does not change.
On the other hand, when the sensor coil 25 is moved in the direction of the axis C2 in a state in which the axis C1 of the tube T and the axis C2 of the sensor coil 25 are orthogonal to each other in a plan view seen in parallel with the arrow A shown in FIG. The value E of the induced electromotive force generated in the sensor coil 25 changes greatly.
More specifically, as shown in FIG. 5, the value E of the induced electromotive force becomes the largest when the sensor coil 25 is located immediately above the axis C <b> 1 of the tube material T. As the sensor coil 25 moves away from directly above the axis C1 of the tube T, the value E of the induced electromotive force decreases.

In this way, by measuring the value E of the induced electromotive force with the voltmeter 30 while moving the sensor coil 25 while changing the direction of the axis C2 of the sensor coil 25, the direction in which the tube T extends in a plan view can be obtained.
In addition, the inclination of the axis C1 of the pipe T with respect to the ground surface G2 can be obtained by performing the above-described process at a plurality of locations along the axis C1 of the pipe T.

The tube material T is embedded immediately below the position where the value E of the induced electromotive force is maximized by moving the sensor coil 25.
In step S16, using the induced electromotive force value E measured at this position, the earth covering Z is obtained from the equation (5).
In addition, (5) Formula shows the above-mentioned (4) Formula more clearly, (5) Formula and (4) Formula are the same.

In addition, when the pipe material T is deeply buried as shown by a position P6 in FIG. 1, the sensor coil 25 detects a magnetic field generated from the pipe material T at the position P7. At this time, the strength of the magnetic field received by the sensor coil 25 is smaller than that when the tube T is shallowly buried, and the value E of the induced electromotive force generated in the sensor coil 25 is also reduced.
For this reason, it turns out that the earth covering Z is long because the value E of the induced electromotive force becomes small in the equation (5).

Here, the combination of the transmitter 2, the sensor coil 25, and the signal processor 3 of the pipe locating system 1 shown in FIG. 6 will be described.
The transmitter 2 </ b> A includes the current supply device 10 </ b> A and the ammeter 20 </ b> A configured in the same manner as the transmitter 2 and configured similarly to the current supply device 10 and the ammeter 20. The transmitter 2A has, for example, substantially the same configuration as the transmitter 2 from a manufacturer (manufacturer).
The sensor coils 25 </ b> A and 25 </ b> B are configured in the same manner as the sensor coil 25. The sensor coils 25 </ b> A and 25 </ b> B have substantially the same configuration, for example, different from the sensor coil 25 from the manufacturer.
The signal processor 3 </ b> A includes a voltmeter 30 </ b> A configured similarly to the signal processor 3 and configured similarly to the voltmeter 30. The signal processor 3A has, for example, substantially the same configuration as that of the signal processor 3 from a different manufacturer.

  In the present embodiment, the pipe locating system 1 is configured using the transmitter 2, the sensor coil 25, and the signal processor 3. However, any one of the transmitter 2 and the transmitter 2A, any one of the sensor coil 25, the sensor coil 25A, and the sensor coil 25B, and any one of the signal processor 3 and the signal processor 3A is used. Even if the pipe locating system is configured, the constant K is obtained in advance using the selected configuration. Thereby, even if a manufacturer combines a transmitter, a sensor coil, and a signal processor which are different from each other, by using the constant K obtained according to the combination, the earth covering Z is obtained from the equation (5). It can be used similarly to the pipe locating system 1.

As described above, the current supply device 10 has a resolution and cannot output an alternating current value as a continuous value. The resistance value between the first position P1 and the second position P2 of the tube material T varies depending on the length between the positions P1 and P2, the material of the tube material T, and the like. For this reason, regardless of the pipe material T, an alternating current having a predetermined value of, for example, 1.00 A, which is set in advance between the first position P1 and the second position P2 of the pipe material T cannot be allowed to flow.
According to the pipe locating method and the pipe locating system 1 of this embodiment, for example, by continuously changing the resistance value of the variable resistor 15 from a state where the value of the alternating current is 0.99 A, the pipe material T The value of the flowing alternating current can be set to a predetermined value of 1.00 A.
Since the value of the alternating current flowing through the tube T for each measurement becomes a predetermined value, there is no error in the alternating current value due to the measurement, and the alternating current value I in equation (5) becomes constant. Therefore, the measurement of the earth covering Z of the pipe material T is stabilized, and the earth covering Z can be measured with high accuracy.

By changing the value of the alternating current while reducing the resistance value of the variable resistor 15, the value of the alternating current flowing through the current supply device 10 and the ammeter 20 gradually increases. Thereby, it is possible to prevent an excessive alternating current from flowing through the current supply device 10 and the ammeter 20, and to prevent damage to the circuits and the like in the current supply device 10 and the ammeter 20.
Using the variable resistor 15, the value of the alternating current flowing through the tube T is set to a value not less than the median value and not more than the upper limit value in the measurement range of the value of the alternating current by the ammeter 20. The ammeter 20 has a measurement error such as 0.5 class. By setting the value of the alternating current flowing through the tube material T in this way, the value of the alternating current flowing through the tube material T with respect to the measurement error of the ammeter 20 increases, and the error in the value of the alternating current decreases. Therefore, the earth covering Z of the pipe material T can be measured with higher accuracy.

Regardless of the presence or absence of coating of the tube material T and the state of the tube material T, inspection in a wide range (several hundred m to 1 km) is possible in the longitudinal direction of the tube material.
Application to a route in which the buried object other than the tube material T and the tube material T are in metal touch (metal members are directly connected) becomes possible.
In particular, it is possible to improve the detection accuracy of the burying position (offset, earth covering) when performing the above-described metal touch.

Here, for example, an example of the resistance value when the pipe material T is a steel pipe having a nominal diameter of 50A and the lead wire 35 has an outer diameter of 1.6 mm will be described.
The total resistance value of the tube T and the lead wire 35 was 5.324 .OMEGA. When the distance between the first position P1 and the second position P2 was 500 m, and 10.648 .OMEGA. When the distance was 1000 m. .

In this embodiment, the pipe locating system 1 may include a control unit, and the control unit may automatically obtain the earth covering Z. Although not shown, the control unit includes an arithmetic element, a memory, and the like. The control unit is connected to the transmitter 2, the signal processor 3, and the variable resistor 15. The variable resistor 15 is provided with a drive motor, and the dial unit 15b is operated based on an instruction from the control unit.
The operator of the pipe locating system 1 inputs the outer diameter D of the pipe material T, the distance L from the ground surface G2 to the center of the sensor coil 25, and the constant K from the input means to the control unit. These values are stored in the memory of the control unit.

The modified pipe locating system 1 configured as described above operates as follows.
The control unit operates the dial unit 15b so that the value I of the alternating current flowing through the tube T measured by the ammeter 20 becomes, for example, the above-described 1.00A. The alternating current value I measured by the ammeter 20 is transmitted to the control unit.
The value E of the induced electromotive force generated in the sensor coil 25 measured by the operator while moving the sensor coil 25 is measured by the voltmeter 30. The value E of the induced electromotive force measured by the voltmeter 30 is transmitted to the control unit. The arithmetic element of the control unit uses the outer diameter D, the distance L, the constant K, and the alternating current value I and the induced electromotive force value E transmitted from the ammeter 20 and the voltmeter 30, stored in the memory. The earth covering Z is obtained from the above equation (5).

As mentioned above, although one embodiment of the present invention has been described in detail with reference to the drawings, the specific configuration is not limited to this embodiment, and modifications, combinations, and deletions within a scope that does not depart from the gist of the present invention. Etc. are also included.
For example, in the said embodiment, the value of the alternating current sent through the pipe material T after adjusting with the variable resistor 15 was set to 1.00A. However, this value can be appropriately set to, for example, 1.50 A, 2.00 A, or the like according to the measurement range of the alternating current value by the ammeter 20.

1 Pipe locating system 10, 10A Current supply device 15 Variable resistor 20, 20A Ammeter (current measurement device)
25, 25A, 25B Sensor coil (coil device)
30, 30A Voltmeter (Voltage measuring device)
P1 1st position P2 2nd position T Pipe X Longitudinal direction Z Earth covering

Claims (4)

A pipe locating method for measuring the earth covering of a pipe formed of metal and buried in the ground,
Supplying an alternating current between a first position and a second position spaced apart in the longitudinal direction of the tube;
The value of the alternating current is changed using a variable resistor capable of continuously changing the resistance value, and the value of the alternating current is set to I which is a predetermined value,
Measure the value E of the induced electromotive force generated in the coil device placed on the ground due to the change of the magnetic field due to the alternating current,
Pipe locating characterized in that the earth covering Z is obtained from equation (1), where L is the distance from the ground surface to the center of the coil device, D is the outer diameter of the pipe material, and K is a constant. Method.
Z = (K × I) / E−L−D / 2 (1)   2. The pipe locating method according to claim 1, wherein when changing the value of the alternating current using the variable resistor, the value of the alternating current is changed while reducing the resistance value. The value of the alternating current is measured with a current measuring device,
3. The pipe locating method according to claim 1, wherein the predetermined value is a value not less than a median value and not more than an upper limit value in a measurement range of the value of the alternating current by the current measuring device. A pipe locating system that measures the earth covering of a pipe formed of metal and buried in the ground,
A current supply device for supplying an alternating current between a first position and a second position spaced apart in the longitudinal direction of the tube;
A variable resistor capable of continuously changing the resistance value and changing the value of the alternating current;
A current measuring device for measuring the value of the alternating current;
A coil device that is arranged on the ground and generates an induced electromotive force due to a change in magnetic field due to the alternating current;
A voltage measuring device for measuring a value of the induced electromotive force generated in the coil device;
A pipe locating system comprising:

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