JPS6166979A - Measuring method of position of underground body - Google Patents

Abstract

PURPOSE:To measure the position of the underground body with high precision by switching and supplying AC currents of <=2 frequencies to a magnetic field producing means and finding each inflection point of the induced voltage characteristic of each frequency of a magnetic field detecting means. CONSTITUTION:Alternating currents from an oscillator 5 of frequency f1 and an oscillator 6 of f2 are switched through a switch 7 and supplied to the oscilla tion coil 2 of a tunnel digging machine 1. The induced voltage across a receiving coil 3 is inputted to a voltage measuring instrument 13 through a BPF11 of frequency f1 or BPF12 of frequency f2 by a switch 10. Then when the induced voltage characteristic of the coil 3 is denoted as F1 when the frequency f1 is selected through the associative switching of the switches 7 and 10 or as F2 when the frequency f2 is selected, distances Y1 and Y2 between inflection points of both characteristics and a reference point P are found. Then, the real distance after the influence of a nearby metallic body 4 is removed is calculated from a specific expression.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for measuring the position of an underground object such as a buried pipe or a tunnel boring machine with high precision.

(Prior art) Conventionally, the position of the underground object of the type described in -1- is ^l/Jl
For example, as shown in Figure 4,
6. Install the transmitting coil 2 (magnetic field generation means) in the tunnel excavation ill as the measurement target so that the axis of the central magnetic field is vertical, and set it on the ground! -, while keeping the magnetic flux linkage plane of the receiving coil 3 (magnetic field detection means) vertical, the receiving coil 3
is scanned in the horizontal direction, and the position W where the induced voltage in the receiving coil 3 is minimum (corresponding to the inflection point of the induced voltage characteristics)
) to find the position of the generator coil 2, that is, the horizontal ()7 position of the tunnel tunnel excavator 1. P is the reference position, and Y is the distance from the reference position P to the horizontal position of the excavator 1.

However, this method allows highly accurate position measurement when there are no metal objects near the transmitting coil 2 or the receiving coil 3, but as shown in FIG.
If there is a magnetic field (secondary magnetic field) generated by the eddy current induced in the metal body 4, the receiving coil
The position where the induced voltage is the minimum is a distance Y (> Yr
) (It will be located J away.

That is, the position of h4 small of the induced voltage II in the receiving coil 3 is shifted from the original position, and its n1 measurement (
A is a value that includes an error.

As described above, the conventional measuring force method has the drawback that it cannot guarantee surface-accurate measurement.

(Objective of the Invention) The present invention was made in 42 to solve this problem, and its main purpose is to measure n1 using two or more frequencies and eliminate the influence of nearby metal objects from the needle measurements at each frequency. It is an object of the present invention to provide a method for measuring the position of an underground object, which allows the position of an underground object to be determined with high precision.

(Structure of the Invention) For this purpose, in the present invention, alternating currents of two or more frequencies are switched and supplied to a single stage of magnetic field generation. From the 1-recording frequency, 1-6 of the object being recorded is made to be 1ill'1.

(Actual AIM Example) Examples of the present invention will be described below. Figure 1 is the fruit h&! An example is small items. In addition, Figures 4 and 5
Identical to the one shown below in the figure, the same symbol (゛・) was changed to ``a'' and ``1'' later. 5 is the oscillator of frequency f1, b is the frequency [2
7 is an oscillator, 7 is a changeover switch, and 8 is an amplifier. Then, the alternating current from the excavator 5 or 6 is supplied to the transmitter coil 2 in the excavator 1. 1) 31, after being amplified, 31 to J exchange switch I O
, and manually performs the measurement 'a13' via the pan 1' pass filter 11 with the IS wave number r+ or the band pass filter 12 with the LJ frequency '6Jl number f2.

Part 1 of FIG. 1 shows the measurement results, in which the frequency f is set by interlocking switching of changeover switches 7 and 10.

Select oscillator 5 and Han I-pass soiler 11 of frequency 11 IJ1! The characteristic of the induced 'iu in the receiving coil 3 when the signal is switched is shown by Fl, and the characteristic when the oscillator 6 of the frequency f2 and the bandpass filter 12 are selected is shown by F2. Fo is a characteristic when the nearby metal body 4 does not exist. Also, YI is the inflection point (minimum voltage point) of characteristic FI
The distance from the reference point P obtained by Y2 is a similar distance obtained at the inflection point of the characteristic F2, and Yr is the true distance.

Here, an aluminum plate or a steel plate is placed as the nearby metal body 4 between the transmitting coil 2 and the receiving coil 3 in the dimensional relationship shown in FIG. The relationship with frequency f was investigated (Figure 3).

As shown in FIG. 3, below the frequency specific to each object, the measurement error closely matches a solid line with a slope of 2 (a solid line in which the measurement error is proportional to the square of the frequency). Also,
When considering the coil of resistor R1 and inductance L as a nearby metal body, we theoretically considered it as follows: Y-Yr=C+/(C2"1/f")=・(
Eleven relationships were obtained. Here, CI and C2 are constants related to R, L, etc. described above. This equation (1) means that in the low frequency range, the mt[ll error is proportional to the square of the frequency, and in the surface frequency range, the difference is constant. Explains the results well.

Therefore, in the low frequency range, the constant 02 can be ignored, so the theory of the following equation holds true.

That is, in general, when the frequency f is equal to or higher than l K IIZ culm, the frequency f and the Ml measured value Y have the following relationship: Y - Yr = αf'' -121. Here, α is It is a fixed constant (corresponding to CI).Therefore, the frequency\If+
, F2, respectively, Y + −Y r−α
f, 2...(3) Y2 -Yr-
af22 ・i41 is established. Taking the difference between 3) and (4) into this equation, YI Y2 = tX
(f+ ” (22) ・i51. Here, Yl and Y2 are n1 measured values, and r,,r, are known, so the constant α can be found from equation (5). That is, , (X-("l'l Y2) / (f+ '
F2”) −1fil.Using this equation (6),
From formula (3), Yr is Yr-YI-f+'
(YI Y2)/ (f+ 2- f22
)...(7) is given by.

For example, if f, = 2f2, equation (7) becomes an even simpler equation, Yr=Y+ -4(YI-Y2)/3 -(4Y2 YI)/3...(8), and the nearby metal A distance 1i11fYr indicating the true horizontal position excluding the influence of the body 4 can be obtained.

In addition, in the example described above, measurements were made using two types of frequencies, but 31! The above measurement can be performed, and in this case, the position of the underground object can be measured by finding the constant 02 of equation +11. Furthermore, in the embodiments described above, the inflection point of the induced voltage characteristic of the receiving coil 3 as the magnetic field detection means is obtained as the minimum voltage value, but if the magnetic field generation means and the magnetic field detection means are slightly modified, It is also possible to obtain the inflection point as the highest voltage value.

(Effects of the Invention) As described above, according to the present invention, it is possible to eliminate the influence of nearby metal objects, so the position of underground objects such as buried pipes and tunneling machines can be determined at +E6 degree. .

Therefore, for example, in a tunnel excavating machine, every time a high precision position 81 measurement result is obtained, surface-accurate direction control 30 becomes TIJ function, and even underground pipes can be easily managed. There are some advantages to doing so.

[Brief explanation of drawings]

Fig. 1 is an explanatory diagram of the a1 measurement method according to an embodiment of the present invention;
The figure is a diagram explaining the dimensions of the experiment, Figure 3 is an 81 measurement difference characteristic diagram that does not show the experimental results, Figure 4 is a diagram explaining the conventional measurement when there is no nearby metal body, and Figure 5 is a diagram explaining the measurement when there is no nearby metal body. It is an explanatory diagram of conventional measurement when it exists. 1. Screaming machine, 2. Explosive coil, 3.
...Receiver (, (coil, 4...nearby metal body, 5.6...
- Oscillator, 7... Selector switch, 8.9... Amplifier,
1() - J exchange switch, 11.12... Han I pass filter, 13... Voltage measuring device. Patent applicant lJ Hon Telegraph and Telephone Public Corporation? 1 Representative Attorney Shikiaki Nagao

Claims (1)

[Claims] (1) A magnetic field generating means is provided in an underground object such as a buried pipe or a tunneling machine, and a magnetic field detecting means that detects the magnetic field from the magnetic field generating means is scanned on the ground, and the magnetic field detecting means detects the magnetic field. In the method of measuring the position of the underground object based on the inflection point of the induced voltage characteristics, alternating current of two or more frequencies is switched and supplied to the magnetic field generating means, and the induced voltage characteristics of each frequency in the magnetic field detecting means are determined. A method for measuring the position of an underground object, characterized in that the position of the underground object is measured from each inflection point and each of the frequencies.