JP7593902B2 - Inner space displacement measurement method - Google Patents

Description

The present invention relates to a method for measuring internal displacement of a tunnel using a 3D scanner.

In tunnel construction, the safety and quality of the work are ensured by periodically measuring the displacement of the ground and support members (A-measurement). By periodically measuring the tunnel condition, it is possible to predict the ground condition in front of the tunnel face and to judge the suitability of the support structure. A-measurement is generally carried out by setting control sections at regular intervals and measuring the coordinates of targets set on the top or side walls of the tunnel at the control sections using a range finder such as a total station (see, for example, Patent Document 1).
In addition, the conventional A-measurement predicts the displacement of the surrounding wall surface (surface) based on the displacement at the installation point (point) of the target. Therefore, in order to measure the displacement of the tunnel wall surface, the shape of the tunnel wall surface may be measured by a 3D scanner.
For example, Patent Document 2 discloses a method for measuring displacement inside a tunnel, in which multiple targets are placed on the tunnel wall, the shape of the tunnel wall including the targets is measured using a 3D scanner, and cross-sectional shape data of the tunnel at the same location is compared based on the coordinates of the targets to track the displacement of the tunnel.
In addition, targets used for measurement by 3D scanners are generally plate-shaped and spherical. Plate-shaped targets are inexpensive, but the measurement accuracy is greatly affected by the positional relationship with the scanner, for example, the angle. On the other hand, spherical targets are very expensive because they use elaborate spheres. Therefore, if a spherical target is used for the purpose of high-precision measurement in the tunnel interior displacement measurement method of Patent Document 2, construction costs may become even higher. In addition, in the method of identifying point information using a spherical target, it is necessary to perform processing assuming the radius of the sphere.

JP 2004-170164 A JP 2014-002027 A

From this perspective, the present invention aims to propose a method for measuring internal displacement that uses a 3D scanner to perform A-measurement more simply, inexpensively, and with higher accuracy.

The present invention for solving the above problem provides an internal displacement measurement method for measuring the shape of a tunnel wall surface by a 3D scanner, in which a triangular or quadrangular pyramid-shaped target is provided on the wall surface of the tunnel with its apex pointing downward to the bottom surface of the tunnel , and coordinate data of the apex of the target is calculated based on the results of measuring a plurality of faces of the target by the 3D scanner . The target is preferably provided at the upper part of the tunnel.
According to this method for measuring internal displacement, it is possible to measure including position information by combining the measurement data of the tunnel wall surface by the 3D scanner and the measurement data of the target. In addition, since the tunnel wall surface is measured by the 3D scanner, it is not necessary to install multiple targets on the same cross section, and the effort and cost required for installing targets can be reduced.
The coordinate data of the vertex of the target is obtained by measuring three or more measurement points on at least three faces of the target, calculating an equation of the face using these measurement points, calculating an intersection of the three faces from the calculated equation, and setting the intersection as the vertex of the target. In this way, the vertex of the target can be identified with high accuracy. By calculating the coordinates of the vertex of the target with high accuracy, the displacement of the target position can be measured more accurately, and the change in the shape of the interior of the tunnel including the target can be accurately grasped.

The internal space displacement measurement method of the present invention makes it possible to perform A-measurement using a 3D scanner easily and inexpensively while improving accuracy.

1 is a cross-sectional view showing an overview of a displacement measuring method according to an embodiment of the present invention. FIG. 2 is a plan view of the target as seen from below.

In an embodiment of the present invention, a method for measuring displacement during construction of a mountain tunnel will be described, in which a 3D scanner 2 is used to periodically measure the wall shape of a tunnel 1 instead of the A measurement using a total station. In general, the internal displacement measurement is performed by measuring tunnel surveying targets installed on the side walls and top of the tunnel 1 at a management section set at regular intervals as the tunnel 1 is excavated using a total station. On the other hand, in this embodiment, the wall shape of the tunnel 1 is measured (scanned) using a 3D scanner 2. FIG. 1 shows the measurement situation using the 3D scanner 2. As shown in FIG. 1, three triangular pyramid-shaped targets 3 (see FIG. 2) installed at the top and left and right of the tunnel 1 (only the target 3 at the top is shown in FIG. 1) are also measured in conjunction with the measurement of the wall shape of the tunnel 1. FIG. 2 is a perspective view of the target 3. The target 3 in this embodiment is a regular triangular pyramid (regular tetrahedron).
The 3D scanner 2 obtains three-dimensional data (shape) of the measurement object by irradiating a laser light onto the measurement object (tunnel wall surface) and analyzing the time it takes for the reflected light of the laser light to reach the 3D scanner 2, the angle of the reflected light, etc. In other words, the measurement by the 3D scanner 2 captures the planar shape by processing a large amount of point cloud data.

The target 3 is attached to the shotcrete 4 sprayed onto the natural ground G (the wall surface of the tunnel 1) exposed during the excavation of the tunnel 1. In this embodiment, the target 3 is attached to the lower end of a jig 5 fixed to the shotcrete 4. The target 3 is provided facing downward so that one vertex 6 of its four vertices points toward the bottom surface of the tunnel 1.
When measuring the target 3, as shown in Fig. 2, three or more measurement points (plots) 8, 8, ... are measured on each of the three faces 7, 7, 7 of the target 3. The data of the measurement points 8 is extracted data of the laser light irradiated on the face 7. Note that the accuracy of identifying the face 7 improves as the number of measurement points 8 increases.
The equation of each surface 7 is calculated from three or more measured measurement points 8, 8, .... The coefficients (a, b, c, d) of the plane equation (Equation 1) are found from the coordinates (x, y, z,) of each measurement point 8. Equation 2 shows the plane equation of the three surfaces 7, 7, 7.

The coordinates ( _xp , _yp , _zp ) of the intersection of the three faces 7, 7, 7 are calculated from the equations (Equation 2) of the calculated three faces 7, 7, 7. The coordinates of this intersection are set as the coordinates of the vertex 6 of the target 3.
The wall surface of the tunnel 1 is measured periodically using a 3D scanner 2, and the internal displacement at the top of the tunnel 1 is grasped from the change in the coordinates of the apex 6 of the target 3. In addition, the exact position of the measurement data of the wall surface shape of the tunnel 1 is grasped from the position of the apex 6 of the target 3, and the internal displacement is grasped by comparing with the existing wall surface shape of the tunnel 1 (past measurement data).
Internal displacement measurements will be carried out periodically as construction of tunnel 1 progresses.

According to the internal displacement measurement method of this embodiment, by combining the measurement data of the tunnel wall surface obtained by the 3D scanner 2 with the measurement data of the target 3, it becomes possible to perform measurements including position information.
Furthermore, since there is no need to install a plurality of targets 3 on the same cross section, the effort and cost required for installing the targets 3 can be reduced.
Furthermore, by measuring the surface 7 of the triangular pyramid-shaped target 3, the coordinates of the apex 6 of the target 3 can be accurately calculated. Therefore, the change in the position of the target 3 (displacement of the apex 6) can be measured more accurately, and the displacement (change over time) of the shape of the interior of the tunnel, including the target 3, can also be accurately grasped.
This eliminates the need to measure multiple targets using a total station. In addition, while the conventional A-measurement method measures the displacement at the target position, the internal displacement measurement method of this embodiment makes it possible to grasp the change in the internal shape of the tunnel 1 three-dimensionally, enabling more accurate displacement measurement.
Since the position of the apex 6 of the target 3 can be calculated with high accuracy, even if the wall shape is measured at an arbitrary position, it is possible to correlate it with other sections. Therefore, it is possible to perform three-dimensional measurement over the entire length of the tunnel 1.
Since it is possible to manage using an arbitrary coordinate system, it is possible to perform accurate measurement of internal space variations while reducing the effort required for complex coordinate calculations.
Furthermore, the target 3 only needs to have three or more faces 7 that intersect at one point, and since the shape is simpler than that of a conventional target made of an elaborate sphere, it can be produced relatively inexpensively and is economical.
The scanned data is instantly processed as image data (electronic data) and can be viewed on various terminals. This allows multiple people to view the data at the same time in multiple locations, reducing the time and effort required for reporting on the progress of construction work.

Although an embodiment of the present invention has been described above, the present invention is not limited to the above-described embodiment, and each of the above-described components can be appropriately modified without departing from the spirit of the present invention.
In the above embodiment, a case has been described in which three targets 3 are provided per measurement cross section, but the number and locations of the targets 3 are not limited, and for example, five targets 3 may be provided per cross section.
In the above embodiment, the target 3 has a triangular pyramid shape. However, the target 3 may have a quadrangular pyramid shape.
In addition, in the above embodiment, a case has been described in which all of the multiple targets 3 arranged on one cross section are triangular pyramid shaped, but only one of the multiple targets 3 may be triangular pyramid or quadrangular pyramid shaped, and the other targets may be general tunnel surveying targets (e.g., prisms).
The target 3 may be fixed to the tunnel 1 or may be provided removably to the tunnel 1 .
In the above embodiment, the target 3 is attached to the shotcrete 4, but the location where the target 3 is attached is not limited, and the target 3 may be attached to, for example, a steel support.
The target 3 and the jig 5 may be separate bodies or may be integrated together.

1 Tunnel 2 3D scanner 3 Target 4 Shotcrete 5 Jig 6 Apex 7 Face 8 Measurement point G Natural ground

Claims (3)

A method for measuring internal displacement of a tunnel by using a 3D scanner to measure the wall shape of the tunnel,
A triangular or quadrangular pyramid-shaped target is provided on a wall surface of the tunnel , facing downward with its apex pointing toward the bottom surface of the tunnel ;
The method for measuring internal displacement comprises calculating coordinate data of vertices of the target based on results of measuring a plurality of surfaces of the target by the 3D scanner . 2. The method for measuring displacement in an inner space according to claim 1 , wherein the target is provided at an upper portion of the tunnel. measuring three or more measurement points on at least three faces of the target;
Calculating an equation of the surface using the measurement points;
3. The method for measuring displacement in an internal space according to claim 1, further comprising the steps of: calculating an intersection of the three surfaces from the calculated equation; and setting the intersection as a vertex of the target.

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