JPH0321046B2 - - Google Patents

Description

[Detailed Description of the Invention] (3-1) Industrial Application Field The present invention relates to a method for measuring displacement inside a tunnel, and more specifically, a laser beam emitted from a reference point is used, and the brightness of the beam is determined by Utilizing the property of normal distribution around the axis, a through hole slightly smaller than the spot diameter and two pairs of photoelectric conversion elements placed around the through hole are used to create a connection between the center point of the photoelectric conversion element and the optical axis. The present invention relates to a method of calculating the amount of displacement of the tunnel, correcting the amount of displacement using a pair of pulse motors, and detecting the amount of correction to measure the displacement in the tunnel.

(3-2) Prior art Generally, when constructing a tunnel using NATM, it is essential to understand the behavior of the surrounding ground and the behavior of the tunnel as a structure for construction management. The most important factor is the displacement inside the tunnel.

Conventionally, a so-called comparience measurer was used to measure the displacement situation inside the tunnel.
A method was used to measure the distance between base point anchors that were previously installed on the tunnel inner wall surface, but this method had poor measurement accuracy and was prone to individual differences, and in the case of large tunnels, it was difficult to use scaffolding for measurement. Moreover, there are many problems such as not being able to do other work during measurement, requiring a lot of manpower, and furthermore, there are disadvantages such as not being able to carry out continuous measurement.

Recently, measurement methods using laser beams have also come into use. One method is to detect the position of the machine by shining a laser beam onto the light receiving plate of a machine installed in the tunnel, and then converting the displacement of the tunnel interior from the machine's position relative to the tunnel interior. However, this method has the disadvantage that the displacement inside the tunnel cannot be directly determined. Another method is to install a rangefinder using a laser beam on the cross section of the tunnel, rotate it to determine the cross-sectional shape of the tunnel, and calculate the displacement of the tunnel interior from this. However, this method also had the disadvantage that the displacement inside the tunnel could not be directly determined, the rangefinder was expensive, required manpower, and remote control was not possible.

(3-3) Purpose of the Invention The present invention eliminates the drawbacks of the conventional method of measuring the inside of a tunnel as described above, and provides a method that does not require manpower, is therefore inexpensive, does not require bulky equipment, and can be remotely controlled. The purpose of this study is to provide a method for measuring displacement inside a tunnel that can be measured continuously.

(3-4) Structure and operation of the invention According to the present invention, a laser beam irradiated in one direction has a spot diameter of a predetermined size depending on the distance from the light source, and the brightness is centered around the optical axis of the laser beam. This was done by paying attention to the fact that , which has a normal distribution, and achieved the above objective by using the following method. In other words, the spot to be measured has a through hole that is slightly smaller than the spot diameter at that location, and the surrounding area is
A light receiving device with two pairs of photoelectric conversion elements arranged on the left and right is installed, receives the light beam from the laser beam, converts the amount of displacement between the optical axis of the laser beam and the center of the photoelectric conversion element into an electric signal, and further A displacement detection device converts the unbalance of the electrical signal into a pulse signal, a pulse motor moves the light receiving device until the laser optical axis and the center of the photoelectric conversion element coincide, and the amount of movement is measured by a displacement meter. Then, the displacement inside the tunnel is measured.

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the method for measuring displacement inside a tunnel according to the present invention will be described below with reference to the drawings. First, the principle of the present invention will be described. Laser beams are light emitted by stimulated emission when electromagnetic waves are applied to various materials, and they have extremely strong coherence and very sharp directivity. That is, unlike natural light, the light emitted from the laser light source has a strong tendency to travel in a straight line, but as shown in FIG. Therefore, at a distance l ₁ from the light source 1, the laser beam is irradiated on a circle with a diameter d ₁ (called the spot diameter), and at a distance l ₂ the spot diameter becomes d ₂ . The illustrated Z-Z is the optical axis of the laser beam.

The He and Ne laser beams currently used for surveying, etc., have a brightness within a circle with a spot diameter of d (hereinafter referred to as a spot circle), regardless of the valence of d. It is a normal distribution with the highest point on the axis. Figure 2 shows the situation. In other words, assuming the coordinate axes X-X and Y-Y with the center O of the spot circle 2 as the origin, and measuring the brightness along the axis X-X, it will be normal as shown in Figure A or Figure B. Distribution curve 3 can be obtained. A curve exactly the same as this curve 3 can be obtained both along the axis Y-Y and along any straight line passing through the center O. Next, a photoelectric conversion element such as a solar cell is moved along this straight line XX, and the voltage generated is measured.
Since the voltage generated by a normal photoelectric conversion element is proportional to the brightness of the received light, a normal distribution curve similar to curve 3 can be obtained from the measured value.

Now suppose an arbitrary circle 4 in spot circle 2,
A photoelectric conversion element 5- is placed at the intersection of this circle 4 and the X-X axis.
Try installing 1,5-2. When the center of the circle 4 and the center O of the spot circle 2 coincide as shown in FIG. 2A, the voltage generated by the elements 5-1 and 5-2
If e ₁ and e ₂ are used, e ₁ = e ₂ as shown. However, as shown in Figure B, when the center O' of the circle 4 and the center O of the spot circle 2 are shifted on the X-X line, e ₁ ≠ e ₂ and the potential difference △e
occurs. This relationship is the same for the Y-Y axis, and if the centers O and O' are shifted on the Y-Y axis, the photoelectric conversion element 5-3 installed at the intersection of the Y-Y axis and the circle 4, A potential difference Δe' occurs between the voltages e ₃ and e ₄ generated from 5-4. If the center O' is shifted from the center O at any position within the spot circle 2, potential differences Δe and Δe' occur simultaneously. The principle of the present invention is to utilize this potential difference to measure the displacement inside the tunnel using a displacement detection device or the like.

Next, the configuration and operation of the light receiving device, displacement detecting device, etc. installed at the measured position will be explained. FIG. 3 is a diagram showing a schematic configuration of the light receiving device 11 and the like. In the figure, the light receiving device 11 is connected to the board 12.
A through hole 13 provided in the center of the through hole, two pairs of photoelectric conversion elements 5-1, 5- provided above, below, left and right of the through hole.
2, 5-3, 5-4, attached to the board 12,
It consists of a female screw 14A having an axis in the left-right direction and a female screw 14B having an axis in the vertical direction. The diameter of the through hole 13 is slightly smaller than the spot diameter of the laser beam at this measured position, and the diameter of the circle 15 passing through the center points of the two pairs of photoelectric conversion elements 5-1, 5-2, 5-3, and 5-4. The diameter is the same as or slightly smaller than the spot diameter. The center of the circle 15 is assumed to be O', and with this O' as the origin, the X-X axis runs in the horizontal direction on the diagram, and the Y-Y axis runs in the vertical direction on the diagram. It is desirable that the circle 15 and the through hole 13 are concentric circles.

The displacement detection device 21 consists of a displacement detection section and a pulse generation section (both not shown).

The correction device 31 consists of a pair of pulse motors 32 and a shaft 33.
The shaft 33A of A is installed parallel to the axis X-X and has a thread, which is the female thread 14A described above.
are screwed together. Also other pulse motor 32B
The shaft 33B is installed parallel to the axis Y-Y and is screwed into the female thread 14B.

Assume that the center O of the spot circle 2 formed by the laser beam is shifted to the left on the X--X line. Naturally, the voltage e ₁ e ₂ generated from the photoelectric conversion elements 5-1 and 5-2 is such that e ₁ >e ₂ and Δe=e ₁ −e ₂ .
The displacement detection device 21 detects this Δe and generates a pulse that causes the pulse motor 32A to rotate counterclockwise when viewed from the direction of its shaft 33A (when viewed from the right side in the figure). Pulse motor 32A
and 32B are pivoted at predetermined positions on the cross section of the tunnel to be measured so that they can freely rotate on a plane perpendicular to the optical axis (the plane shown in the drawing in FIG. 3). moves to the left in the figure. Since pulses continue to be generated until Δe becomes 0, the centers O and O' eventually coincide. When O is offset on the Y-Y axis, the pulse acts on the pulse motor 32B and the board 12 moves along the Y-Y axis. When the center O is shifted to an arbitrary position within the circle 15, the pulse motors 32A and 32B operate simultaneously and the centers O and O' eventually coincide. Displacement meter 41A, 4
The main body of 1B is fixed at a predetermined position on the cross section to be measured like the pulse motors 32A and 32B, and its measurement ends 42A and 42B are connected to the board 12 of the light receiving device.
Since the board 12 is in contact with the board 12, the movement of the board 12 is measured by the displacement meters 41A and 41B, and recorded as necessary.

Next, a method for measuring displacement inside a tunnel using the apparatus described above will be explained step by step.

(a) A laser beam is emitted from a laser light source installed at a reference point in the tunnel in the direction of tunnel travel (direction of the measurement location). The reference point needs to be a fixed point (a point that does not cause displacement) due to its nature. However, the displacement is small,
If the displacement can be measured by some method, it can be used as a reference point by correcting it. As the laser light source, the light source currently widely used for tunnel surveying can be used as is.

(b) The laser beam is received by a light receiving device installed at the measured position in the tunnel. Since the light receiving device is fixed at a predetermined position on the cross section of the tunnel to be measured via a pair of pulse motors, precisely speaking, the displacement measured by this method is the displacement at the predetermined position.

(c) The amount of displacement is detected by the displacement detection device, and based on it, a pulse is sent to the pulse motor of the correction device.

(d) Correction is performed by the pulse motor of the correction device until the center of the photoelectric conversion element of the light receiving device and the optical axis of the laser beam coincide.

(e) The amount of correction is measured by a displacement meter and recorded if necessary. As described above, since the light source of the laser beam is installed at a reference point that is a fixed point, the optical axis of the laser beam is immobile, and therefore the amount of correction is the amount of displacement in the tunnel interior.

(3-5) Embodiments other than the above The embodiments exemplified above mainly describe the case where the measurement target position in the tunnel is one place, but in the method according to the present invention, the laser beam is placed in the center of the light receiving device. Since the through hole is provided with a diameter slightly smaller than the spot diameter of the tunnel, the internal displacement can be measured at multiple locations within the tunnel, as shown in FIG. At this time, as many light receiving devices, correction devices, and displacement meters as there are measurement points are required, but the number of displacement detecting devices is not necessarily necessary, and one is sufficient.

In addition, dust is likely to be generated in work areas inside tunnels, which can harm the working environment, but in order to improve this problem, it is necessary to measure the amount of dust generated. Since the laser beam is absorbed and diffused by dust, the absolute value of the brightness of the light-receiving area depends on the concentration of the dust. Therefore, if the relationship between dust concentration and brightness is determined experimentally, the displacement of the tunnel interior and the dust concentration can be measured simultaneously using the method according to the present invention.

(3-6) Effects of the Invention The present invention uses a laser beam, a photoelectric conversion element, a pulse motor, etc. to constantly correct the center of the light receiving device so that it coincides with the laser beam axis, and records the amount of correction. It has many excellent effects as described below.

Since the surveying laser light source currently used inside the tunnel can be used as is, equipment costs can be reduced.

Multi-point measurement is possible.

It is possible to simultaneously measure the swelling, deformation, etc. of the tunnel wall and the subsidence of the tunnel.

Continuous measurement, continuous recording, and remote measurement are possible. Furthermore, recording processing by a computer is easy.

No manpower is required for measurements, thus reducing operating costs.

Since it can be installed at an appropriate location within the tunnel,
Measurement is possible regardless of the work inside the tunnel.

Measurements of dust concentration can be made simultaneously.

At the same time as measuring long-term displacement such as subsidence and cross-sectional deformation, it is also possible to measure and record vibrations caused by blasting and the passage of machinery, vehicles, etc. This makes it possible to monitor tunnel work from a remote location, making it possible to This can contribute to process control.

The present invention as described above plays a major role in increasing the efficiency of tunnel construction work, ensuring work safety, and reducing construction costs.

[Brief explanation of the drawing]

Figure 1 shows the progression of the laser beam.
Figure 2 shows the principle of the present invention, and shows the relationship between the luminance distribution of the laser beam within the spot circle and the voltage generated by the photoelectric conversion element placed within the spot circle. When the center of each photoelectric conversion element and the center of the spot circle match, B shows the case where they deviate, FIG. FIG. 3 is a diagram showing another embodiment of the present invention. 1... Laser light source, 2... Spot circle, 3...
...normal distribution curve, 4...arbitrary circle, 5-1, 5-
2, 5-3, 5-4... photoelectric conversion element, 11...
Light receiving device, 12... Board, 13... Through hole, 14
A, 14B... Female thread, 15... Circle, 21... Displacement detection device, 31... Correction device, 32A, 32B
...Pulse motor, 33A, 33B...Axis, 4
1A, 41B...Displacement meter, 42A, 42B...Measurement end.

Claims (1)

[Claims] 1. A method for measuring displacement inside a tunnel, which is carried out by the following steps (a) to (e). (a) A laser light source installed at a reference point inside the tunnel emits a conical laser beam in the direction of tunnel travel. (b) A conical laser beam is installed at a measurement point inside the tunnel and is slightly smaller than the spot diameter of the laser beam. (c) The laser beam is received by a light receiving element having a through hole and two pairs of photoelectric conversion elements provided on the upper, lower, left and right sides of the through hole. Analyze the electrical signals received, detect the amount of vertical and horizontal displacement between the center point of the two pairs of photoelectric conversion elements and the laser beam axis, and emit a pulse signal based on this amount of displacement (d) Each of the above-mentioned locations to be measured a pair of pulse motors pivotally supported at predetermined locations on the inner wall surface of the tunnel so as to be rotatable on a plane perpendicular to the laser beam; and a pair of pulse motors connected to the axis of the pulse motors;
and correcting the position of the light receiving device based on the pulse signal until the amount of displacement becomes 0 using a correction device having a male screw threaded into the female thread attached to the light receiving device. and a pair of displacement meters that detect the relative movement of the light receiving device to measure the amount of correction, that is, the displacement in the tunnel. 2. The method for measuring spatial displacement in a tunnel according to claim 1, characterized in that the spatial displacement is measured simultaneously by one light source. 3. The dust concentration inside the tunnel is measured at the same time as the displacement inside the tunnel by experimentally determining the relationship between the electric signal generated by the photoelectric conversion element and the concentration of suspended dust inside the tunnel. A method for measuring displacement inside a tunnel according to claim 1.