JP6876448B2 - Tunnel face forward displacement measurement method - Google Patents

Description

The present invention relates to a tunnel face front displacement measuring method used for measuring the underground displacement in front of a face in tunnel construction such as mountain tunnel construction, and in particular, a tunnel face that simply measures the amount of underground displacement in front of the face from inside the tunnel. Regarding the forward displacement measurement method.

In tunnel construction such as mountain tunnel construction, it is important to evaluate the stability of the tunnel by measuring the underground displacement in front of the tunnel face as the tunnel is dug.
Such measurement of the amount of displacement in the ground is generally performed using an underground displacement meter.
As shown in FIG. 10, in this measurement, first, a long steel pipe having an outer diameter of about 114 mm or 75 mm, a wall thickness of about 5, 6 mm, and a length of 12, 13 m is used as a sheath pipe a, and diagonally forward from the top of the tunnel face. Place. Next, in order to bring the sheath pipe a into close contact with the ground (hole wall), grout b is injected between the sheath pipe a and the ground (hole wall). Then, an underground displacement meter c such as a horizontal inclinometer having an outer diameter of about 50 mm or a pipe strain meter having an outer diameter of about 42 mm is inserted into the sheath pipe a. After inserting the underground displacement meter c into the sheath pipe a, inject grout b into the sheath pipe a so that the underground displacement meter c does not wobble in the sheath pipe a, and then inject the grout b into the sheath pipe a and the underground displacement meter c. To integrate with. The amount of displacement in the ground is measured by the underground displacement meter c placed in the ground in this way.

Further, Patent Documents 1 and 2 have proposed this kind of face forward displacement measuring method.
(1) Patent Document 1 relates to a method for predicting / determining the stability of a tunnel face. In this method, a leading boring hole is formed at the top of the tunnel from the face toward the front side in the excavation direction, and leading boring is performed. A displacement measuring means for measuring the underground displacement in front of the face is installed in the hole, and the measured value measured by the displacement measuring means is compared with the control limit set in advance based on the three-dimensional analysis result to stabilize the face. Predict / judge sex.
In this method, in particular, a leading boring hole having a length L = 80 m, a lap 2D = 24 m (D is a tunnel width; about 12 m in this embodiment), and a diameter φ = 116 mm is drilled above the top of the tunnel with a boring machine. 15 5m connected inclinometers will be installed in this leading boring hole to measure the top-ground displacement in front of the face. The connected inclinometer is provided with a horizontal inclinometer that is movably (swingable) supported by a guide roller in a guide tube having a diameter of, for example, about 75 mm, which is inserted and arranged in the preceding boring hole. It is configured so that the displacement signal of can be output by a converter and an output cable to measure the displacement in the ground. Instead of the connected inclinometer, a pipe type strain meter, an optical fiber strain measurement, an insertion type azimuth / inclinometer, etc. can be used.
By measuring the underground displacement in advance of the top of the tunnel in this way, for example, when constructing a city tunnel with a small soil cover, there are signs of abnormalities such as the collapse of the face of the small soil cover and the depression of the ground surface. Can be detected early in front of the face, and it is possible to prevent the face from collapsing and the surface collapse of the small soil cover.
(2) Patent Document 2 relates to a method of installing a preceding underground displacement meter. In this method, an outer pipe is driven from the tunnel face toward the displacement measurement start point in the ground above the planned tunnel excavation site. Displacement due to the pipe placing process, the inner pipe insertion process of inserting the inner pipe inside the outer pipe and filling the inner space of the outer pipe outside the inner pipe with a solidifying material, and the tearing of the outer pipe and inner pipe accompanying tunnel excavation. A displacement meter installation process in which a bendable displacement meter is inserted into the inner pipe opened in the tunnel excavation surface near the measurement start point, and a curved pipe in the outer pipe opened in the tunnel excavation surface near the displacement measurement start point together with the inner pipe. The other end of the curved pipe is connected to the one end of the tunnel, and the other end of the curved pipe is arranged toward the inside of the tunnel behind the support work installed near the start point of the displacement measurement in the tunnel excavation direction. Therefore, the preceding underground displacement meter is installed without providing a widening part in the tunnel.
In this method, in particular, in the outer pipe driving step, a steel pipe having a predetermined length is driven from the vicinity of the top end of the tunnel face. The steel pipe 5 is, for example, a long steel pipe having a length of about 12 to 13 m, and is provided with a drilling bit at the tip thereof. When placing a steel pipe from the tunnel face to the ground, a heavy machine for drilling such as a hydraulic jumbo placed in the tunnel pit drives the excavation bit at the tip of the steel pipe to perform a drilling operation on the ground, and the steel pipe is tunneled. Gradually excavate from the face to the displacement measurement start point of the ground and further to the displacement measurement end point. In the inner pipe insertion step, a PVC pipe for which a preceding underground displacement meter is set is inserted into the inner space of the steel pipe opened in the tunnel face, and the inner space of the steel pipe outside the PVC pipe and the steel pipe and its surroundings are inserted. The gap space between the ground and the ground is filled with an appropriate solidifying material such as grout, mortar, or resin. By filling the space inside the steel pipe and the gap space and solidifying it in this way, the ground, the steel pipe, and the PVC pipe are integrated, and the displacement that occurs in various behaviors of the ground is almost lossless. Will be transmitted directly to. Further, the inner diameter of the PVC pipe is close to the outer diameter of the preceding underground displacement meter, and the preceding underground displacement meter inserted into the PVC pipe can behave integrally with the PVC pipe. The outer pipe is not limited to the above-mentioned steel pipe, and for example, a GFRP (Glass fiber reinforced plastics) pipe may be adopted. Further, the inner pipe is not limited to the above-mentioned PVC pipe, and for example, a steel pipe may be adopted. Then, in the displacement meter installation step, the ends of the steel pipe and the PVC pipe are exposed on the tunnel excavation surface near the displacement measurement start point due to the breakage of the steel pipe and the PVC pipe accompanying the tunnel excavation. Therefore, a bendable preceding underground displacement meter is inserted into a PVC pipe whose end is open on the tunnel excavation surface near the displacement measurement start point. This bendable preceding underground displacement meter is a displacement meter called a 3D underground displacement meter, and has a structure in which segments of a predetermined pitch with a built-in acceleration sensor are connected, and each segment is flexible. It can be flexed within a certain range by the joints.
In this way, the preceding underground displacement meter can be installed without providing a widening portion in the tunnel.

Japanese Unexamined Patent Publication No. 2016-933 Japanese Unexamined Patent Publication No. 2015-113572

However, the conventional tunnel face forward displacement measuring method has the following problems.
(1) When a steel pipe having an outer diameter of about 114 mm or 75 mm is used as the sheath pipe and the sheath pipe is placed near the top of the tunnel face, a dedicated rock drilling bit or the like is required, which increases the cost. In addition, it takes a lot of time to install the sheath pipe.
Therefore, it is desirable to reduce the diameter of the sheath tube and insert the sheath tube into the measurement hole drilled from the tunnel face toward the front of the face.
(2) In order to ensure the measurement accuracy of the amount of displacement in the ground, it is necessary to grout the sheath pipe (steel pipe) and the hole wall of the ground. Therefore, the sheath pipe (steel pipe) and the hole wall of the ground must be brought into close contact with each other. It is necessary to inject grout between and. Further, when grout is injected into the sheath pipe and the sheath pipe and the underground displacement meter are integrated, the underground displacement meter cannot be recovered and cannot be diverted. For this reason, if the sheath pipe has a double structure of an outer pipe and an inner pipe, there is an advantage that the sheath pipe can be pulled out from the inner pipe and collected, but on the other side, it takes a lot of time to install the sheath pipe.
Therefore, it is desirable to eliminate the need for grout for bringing the sheath pipe into close contact with the ground.
(3) When a steel pipe having a wall thickness of 5 or 6 mm is used for the sheath pipe, the rigidity is high, and it may be difficult for the underground displacement meter in the sheath pipe to follow the displacement of the ground.
Therefore, it is desirable to reduce the rigidity of the sheath pipe so that the underground displacement meter in the sheath pipe can easily follow the displacement of the ground.

The present invention solves such a conventional problem. In this type of tunnel face forward displacement measuring method, the sheath pipe can be installed at low cost and in a short time, and the sheath pipe and the ground are brought into close contact with each other. The purpose is to eliminate the need for a ground to make the tunnel, reduce the rigidity of the sheath pipe, and make it easier for the underground displacement meter in the sheath pipe to follow the displacement of the ground.

In order to achieve the above object, the present onset Ming,
A measurement hole is drilled from the tunnel face to the front of the face, and an underground displacement meter is installed in the measurement hole via a sheath pipe for installing an underground displacement meter that can follow the displacement in the ground. In the tunnel face forward displacement measurement method for measuring underground displacement,
The sheath tube is formed by crushing or compressing and deforming the outer peripheral surface in a tubular shape having a hollow original shape to compress the hollow cross section inside, and by press-fitting a fluid into the inner surface, the outer peripheral surface is pressed by the fluid pressure. Using a tube material that can be expanded in the radial direction and restored to the tubular shape,
The outer peripheral surface is crushed or compressed and deformed, and the sheath tube before restoration is inserted into the measurement hole into the tubular shape.
After inserting the sheath tube before restoration into the tubular shape into the measurement hole, the fluid is press-fitted into the sheath tube before restoration into the tubular shape so that the outer peripheral surface of the sheath tube before restoration into the tubular shape is radialally oriented. Inflated to the tubular shape and brought into close contact with the inner peripheral surface of the measuring hole.
The underground displacement meter is inserted into the restored sheath pipe that is in close contact with the measurement hole, and the restored sheath pipe is made to follow the displacement in the ground and tunneled by the underground displacement meter. Measure the displacement in front of the face,
The gist is that.

Moreover, this measurement method is embodied as follows.
(1) A steel pipe is used in which the outer peripheral surface can be expanded in the radial direction by injecting pressurized water into the sheath pipe and the displacement in the ground can be followed in the measurement hole. Further, a resin tube may be adopted in the sheath tube so that the outer peripheral surface can be expanded in the radial direction by passing vapor pressure inside and the displacement in the ground can be followed in the measurement hole.
(2) A 3D underground displacement meter is adopted, in which a plurality of segments with a built-in acceleration sensor are flexibly connected via flexible joints.

According to the tunnel face forward displacement measuring method of the present invention, the sheath tube is formed by crushing or compressing the outer peripheral surface in a tubular shape and compressing the hollow cross section inside, and press-fitting the fluid into the sheath tube. Using a tube material that can be restored to a tubular shape by expanding the outer peripheral surface in the radial direction with the fluid pressure, insert this sheath tube into the measurement hole and press-fit the fluid into the sheath tube to press the outer peripheral surface of the sheath tube. Is expanded in the radial direction and brought into close contact with the inner peripheral surface of the measuring hole, and an underground displacement meter is inserted inside the sheath tube that is brought into close contact with the measuring hole to displace the sheath tube after restoration in the ground. Since the displacement in front of the tunnel face is measured by the underground displacement meter, the sheath pipe can be installed at low cost and in a short time, and the sheath pipe and the ground can be brought into close contact with each other. The ground can be eliminated, and the rigidity of the sheath pipe can be lowered to make it easier for the underground displacement meter to follow the displacement of the ground, which is a special effect unique to the present invention.

The figure which shows the tunnel face forward displacement measurement method by one Embodiment of this invention. The figure which shows the structure of the sheath tube used in the measurement method ((a) partially broken perspective view (b) of the sheath tube partial cross-sectional perspective view) Diagram showing the configuration of the underground displacement meter used in the measurement method (side view) The figure which shows the process of installing a sheath pipe in the ground in front of a face in the same measurement method. The figure which shows the process of installing the underground displacement meter in the underground sheath pipe in front of the face in the same measurement method. Diagram showing the outline of the field experiment of the same measurement method Diagram showing the results of field experiments of the same measurement method The figure which shows the outline of the laboratory experiment of the same measurement method The figure which shows the result of the laboratory experiment of the same measurement method The figure which shows the conventional tunnel face forward displacement measurement method

Next, a mode for carrying out the present invention will be described with reference to the drawings.
FIG. 1 shows a method for measuring the forward displacement of the tunnel face.
As shown in FIG. 1, in this tunnel face forward displacement measurement method, a measurement hole T10 is drilled from the tunnel face T1 toward the front of the face T1, and a sheath tube 1 is inserted into the measurement hole T10 to insert the measurement hole. An underground displacement meter 2 is installed at T10 via a sheath pipe 1 to measure the underground displacement. The specific procedure will be described later.

In this measurement method, the sheath tube 1 is formed by crushing or compressing and deforming the outer peripheral surface in a tubular shape having a hollow original shape and compressing the hollow cross section inside, and by press-fitting the fluid inside, the fluid pressure is used. Use a tube material that can be restored to a tubular shape by expanding the outer peripheral surface in the radial direction.
Here, a steel pipe whose outer peripheral surface can expand in the radial direction by injecting pressurized water into the sheath pipe 1 is adopted.
As such a steel pipe, a steel pipe expansion type lock bolt generally used for reinforcing the ground is known.
As shown in FIG. 2, the steel pipe expansion type lock bolt 1 is originally a hollow thin-walled steel pipe, which is pressed from the outer peripheral surface 10 to form a plate shape, bent in a tubular shape with the longitudinal direction as an axial direction, and a shaft. It is formed in a C-shaped cross section having a recess 11 extending in the direction. In this case, the lock bolt 1 has an outer diameter of 36 mm, a length of 6 m, a wall thickness of about 2 to 3 mm that can be deformed by the pressure of water supplied to the inside of the steel pipe, and a fluid can flow into the inside of the steel pipe. The steel pipe has a plate shape that is not completely crushed. A sleeve 12 is attached to the tip of the steel pipe thus formed (before the tubular restoration). The sleeve 12 is formed in a cylindrical shape, the tip of the steel pipe is inserted, and the sleeve 12 is fixed by welding or the like. The mouth of the tip of the steel pipe is closed by welding or the like. On the other hand, the sleeve 13 is also attached to the rear end of the steel pipe. The sleeve 13 is formed in a cylindrical shape, and the rear end portion of the steel pipe is inserted and fixed by welding or the like. A water injection hole (not shown) is formed in the axial middle portion of the sleeve 13, and the water injection hole communicates with a through hole (not shown) formed on the rear end side of the steel pipe to form a steel pipe. It communicates inside. The rear end of the steel pipe is closed by welding or the like. In this way, the inside of the steel pipe (before the tubular restoration) is a closed space in which the front end and the rear end are closed, and is communicated with the outside through the water injection hole of the sleeve 13 on the rear end side. To.
In this way, the lock bolt 1 (before being restored to the tubular shape) has a water injection adapter attached to the sleeve 13 on the rear end side, a water injection hose is connected to the water injection adapter, and a water pressure pump or the like is used from the water source. By sending the pressurized water to the water injection hose and supplying it to the inside of the steel pipe through the water injection hole, the pressurized water is injected into the inside of the steel pipe, and the outer peripheral surface 10 of the steel pipe is radially oriented while the recess 11 of the outer peripheral surface 10 of the steel pipe is made smaller. In this case, the inner diameter expands to about 45 mm to 55 mm.
This lock bolt 1 is used as a sheath pipe 1.

Further, in this measurement method, an existing underground displacement meter having a diameter smaller than the inner diameter of the sheath pipe 1, that is, the steel pipe expansion type lock bolt 1 is used for the underground displacement meter 2. Here, the ultrafine 3D underground displacement meter 2 having an outer diameter of 25 mm, which is also described in Patent Document 2, is adopted. As shown in FIG. 3, the ultrafine 3D underground displacement meter 2 is configured by flexibly connecting a plurality of segments 20 incorporating a gravitational acceleration sensor (MEMS) 21 via flexible joints 22.

In this measurement method, using such a sheath pipe 1 and an underground displacement meter 2, the underground displacement in front of the tunnel face is simply measured by the following procedure.
Step 1 (see Figure 1)
First, the measurement hole T10 is drilled diagonally forward from the vicinity of the top of the tunnel face T1.
In this case, a drill jumbo is used for drilling the measurement hole T10, and a rock drilling bit having an outer diameter of 45 mm is used. These devices and devices are used for ordinary tunnel excavation work, and no special machines or devices are required for this drilling.
Step 2 (see Figure 4)
After drilling the measurement hole T10, the sheath tube 1 before restoration is inserted into the measurement hole T10 in a tubular shape as shown in FIG. 4 (1).
In this case, a steel pipe expansion type lock bolt 1 having an outer diameter of 36 mm and a length of 5 m is manually (pushed) and inserted into the measurement hole T10 as a sheath pipe 1.
Since the outer peripheral surface 10 of the sheath tube 1 is crushed or compressed and deformed to form a tubular material having a small diameter before restoration, the sheath tube 1 can be easily inserted into the measurement hole T10. Further, these steps 1 and 2 are substantially the same operations as the rock bolt driving operation normally performed in the mountain tunnel construction, and these operations can be performed in a short time.
Step 3 (see Figure 4)
After inserting the sheath tube 1 before restoration into a tubular shape into the measuring hole T10, then, as shown in FIGS. 4 (2) and 4 (3), the sheath tube 1 before restoration into a tubular shape inside the measuring hole T10 is inside the sheath tube 1. By press-fitting the fluid, the outer peripheral surface 10 of the sheath tube 1 before restoration into a tubular shape is expanded in the radial direction by the fluid pressure and restored to the original tubular shape so as to be brought into close contact with the inner peripheral surface of the measurement hole T10.
In this case, a water injection adapter is attached to the sleeve 13 on the rear end side of the steel pipe expansion type lock bolt 1 used as the sheath pipe 1 to communicate with the water injection hole of the sleeve 13, and the water pressure is connected to the water injection adapter via the water injection hose. Connect the pump. Then, pressurized water is injected into the lock bolt 1 by a hydraulic pump, and the lock bolt 1 (outer peripheral surface 10) is expanded by water pressure to be brought into close contact with the inner peripheral surface (hole wall) of the measurement hole T10. The inner diameter of the lock bolt 1 can be expanded to about 45 mm to 55 mm, and the lock bolt 1 (outer peripheral surface 10) is sufficiently adhered to the inner peripheral surface (hole wall) of the measurement hole T10. As a result, no grout is required between the sheath pipe 1 and the measurement hole T10 (hole wall of the ground), and the grout is injected between the sheath pipe 1 and the measurement hole T10 (hole wall of the ground). No need to do.
Step 4 (see Figure 5)
After expanding the sheath tube 1 in the measurement hole T10, as shown in FIG. 5, the rear end portion of the sheath tube 1, in this case, the end portion on the front side when viewed from the tunnel face T1 side is opened for measurement. The underground displacement meter 2 is inserted into the restored sheath pipe 1 that is in close contact with the hole T10.
In this case, since the sleeve 13 is attached to the sheath tube 1, that is, the rear end side of the lock bolt 1, the rear end side of the lock bolt 1 is cut together with the sleeve 13 to cut the rear end side of the lock bolt 1. To open. Since the inner diameter of the lock bolt 1 is expanded to about 45 mm to 55 mm by expansion, the underground displacement meter 2 can be easily inserted through the opening at the rear end. Then, an extra-fine 3D underground displacement meter 2 having an outer diameter of 25 mm is inserted into the sheath tube 1 from the opening at the rear end.
Step 5 (see Figure 1)
In this way, the underground displacement meter 2 installed in the ground in front of the tunnel face T1 measures the displacement in the ground in front of the face T1.
Then, as the tunnel is dug, steps (1)-(5) are repeated as appropriate.

The applicant of the present application conducted a field experiment of this measurement method in order to confirm the measurement accuracy by this tunnel face forward displacement measurement method. The outline of the field experiment is shown in FIG. 6, and the result is shown in FIG.
As shown in FIG. 6, in this field experiment, the tunnel was dug from the right side to the left side in the figure, and the first day was set as the start of measurement, and the position of the face on the first day was as described above. A measurement hole T10 is drilled diagonally forward from the vicinity of the top of the face, a sheath tube 1 is inserted into the measurement hole T10, and an underground displacement meter 2 is installed in the measurement hole T10 via the sheath tube 1. Then, with this underground displacement meter 2 (hereinafter referred to as the underground displacement meter 2 installed from the mine), the tunnel is set to the initial value (0 (zero)) from the position of the face on the first day to the time on the first day. The displacement in the ground caused by the excavation of the tunnel was measured.
In addition, in order to confirm the measurement accuracy by this tunnel face forward displacement measurement method, how far the ground starts to sink from the front of the tunnel face, whether only the front of the tunnel face is lowered, or the tunnel itself. In order to confirm whether the tunnel is lowered or both are lowered, before the tunnel is excavated, a long underground 20 m in length from the outside of the tunnel is placed at a predetermined position above the planned tunnel excavation position. The displacement meter 3 is installed substantially horizontally, and the underground displacement meter 3 (hereinafter referred to as the underground displacement meter 3 installed from outside the mine) is used to tunnel from a predetermined position behind the face position on the first day. The underground displacement that occurs with the excavation of the tunnel was measured.
The upper part of FIG. 7 shows the displacement in the ground when the position of the face reaches the position on the 4th day (displacement with the time on the 1st day as the initial value (0)). Here, the underground displacement measured by the underground displacement meter 2 installed from inside the mine is a black circle, and the underground displacement measured by the underground displacement meter 3 installed from outside the mine is a white circle. The lower part of FIG. 7 shows the displacement in the ground when the position of the face reaches the position on the fifth day (displacement with the time on the first day as the initial value (0)). Here, the underground displacement measured by the underground displacement meter 2 installed from inside the mine is a black circle, and the underground displacement measured by the underground displacement meter 3 installed from outside the mine is a white circle.
As is clear from FIG. 7, the measurement result by the underground displacement meter 2 installed from inside the mine and the measurement result by the underground displacement meter 3 installed from outside the mine are in good agreement, and this simple tunnel face forward displacement measurement method However, it was confirmed that the underground displacement in front of the face can be measured accurately.

The applicant of the present application also conducted a laboratory experiment to further confirm the measurement accuracy by this tunnel face forward displacement measurement method. The outline of the laboratory experiment is shown in FIG. 8, and the result is shown in FIG.
As shown in FIG. 8, in this laboratory experiment, a steel pipe expansion type lock bolt was used for the sheath pipe 1, an ultrafine 3D underground displacement meter was used for the underground displacement meter 2, and an ultrafine 3D ground was used in the steel pipe expansion type lock bolt 1. By inserting the medium displacement meter 2, one end (in this case, the right end) of the lock bolt 1 is fixed to the pedestal B, and the other end (in this case, the left end) is forcibly pulled up by using the machine M. The rock bolt 1 was bent, the displacement amount was measured by the 3D underground displacement meter 2, and the actual displacement amount of the lock bolt 1 was measured by the external displacement meter 4. Further, in this case, the measurement was performed in two stages, that is, when the lock bolt 1 was bent relatively small and when it was bent relatively large.
FIG. 9 shows the measurement result by the 3D underground displacement meter 2 in a curve graph, and the measurement result (true value) by the external displacement meter 4 in a bar graph. In FIG. 9, the curve graph represented by a curve that bends slightly downward is the measurement result by the 3D underground displacement meter 2 when the rock bolt 1 is bent relatively small, and the displacement amounts are 80.1, 51.9, and 29.0. , The bar graph represented by the bar of 11.9 is the true value at that time. Further, in FIG. 9, the curve graph represented by the curve that bends greatly upward is the measurement result by the 3D underground displacement meter 2 when the rock bolt 1 is bent relatively greatly, and the displacement amount is 20.9, 12.0, 5 The bar graph represented by the bars of 8.8 and 2.0 is the true value at that time.
As is clear from FIG. 9, the measurement result by the 3D underground displacement meter 2 inserted in the steel pipe expansion type lock bolt 1 and the true value measured by the external displacement meter 4 are in good agreement, and this simple tunnel It was confirmed that the front face displacement measurement method can measure the displacement with high accuracy.

As described above, in this tunnel face forward displacement measurement method, a steel pipe expansion type lock bolt is used for the sheath pipe 1, the lock bolt 1 is inserted into the measurement hole T10, and pressurized water is injected into the lock bolt 1. By doing so, the outer peripheral surface 10 of the lock bolt 1 is expanded in the radial direction to be brought into close contact with the inner peripheral surface of the measurement hole T10, and the underground displacement meter 2 is formed inside the lock bolt 1 which is brought into close contact with the measurement hole T10. By inserting an ultrafine 3D underground displacement meter and measuring the displacement in front of the tunnel face T1 with this underground displacement meter 2, the following remarkable effect unique to this measurement method is obtained.
(1) Installation of the sheath pipe 1 in the measurement hole T10 and installation of the underground displacement meter 2 in the sheath pipe 1 can be easily performed, and these installation costs are 5 compared to the conventional construction method. It can be reduced to about one-third.
(2) By making it easy to install the sheath pipe 1 in the measurement hole T10 and the underground displacement meter 2 in the sheath pipe 1, the time required for these installations is compared with the conventional construction method. It can be shortened to about one-fifth.
(3) The grout for bringing the sheath pipe 1 and the ground into close contact with each other is not required, and the grout injection work can be omitted. Further, in this case, since the grout is not injected into the sheath pipe 1 only by inserting the underground displacement meter 2 into the sheath pipe 1, the underground displacement meter 2 is collected from the sheath pipe 1 after the measurement of the underground displacement is completed. Can be diverted. These points can also contribute to cost reduction.
(4) Since the sheath pipe 1 is a thin steel pipe and has low rigidity, the underground displacement meter 2 can easily follow the displacement of the ground, and the measurement accuracy of the underground displacement can be improved.

In this embodiment, a thin steel pipe whose outer peripheral surface can be expanded in the radial direction by injecting pressurized water into the sheath pipe 1 such as a steel pipe expansion type lock bolt is adopted, but instead of this, the inside A resin pipe whose outer peripheral surface can expand in the radial direction by passing vapor pressure through the pipe may be adopted. Even in this way, the same effect as that of the above embodiment can be obtained.

T1 tunnel face T10 measurement hole 1 sheath pipe (steel pipe expansion type lock bolt)
10 Outer surface 11 Recesses 12, 13 Sleeve 2 Underground displacement meter (ultra-fine 3D underground displacement meter)
20 Segment 21 Gravitational Acceleration Sensor 22 Joint 3 Underground Displacement Meter B Pedestal M Machine 4 Displacement Meter

Claims (4)

A measurement hole is drilled from the tunnel face to the front of the face, and an underground displacement meter is installed in the measurement hole via a sheath pipe for installing an underground displacement meter that can follow the displacement in the ground. In the tunnel face forward displacement measurement method for measuring underground displacement,
The sheath tube is formed by crushing or compressing and deforming the outer peripheral surface in a tubular shape having a hollow original shape to compress the hollow cross section inside, and by press-fitting a fluid into the inner surface, the outer peripheral surface is pressed by the fluid pressure. Using a tube material that can be expanded in the radial direction and restored to the tubular shape,
The outer peripheral surface is crushed or compressed and deformed, and the sheath tube before restoration is inserted into the measurement hole into the tubular shape.
After inserting the sheath tube before restoration into the tubular shape into the measurement hole, the fluid is press-fitted into the sheath tube before restoration into the tubular shape so that the outer peripheral surface of the sheath tube before restoration into the tubular shape is radialally oriented. Inflated to the tubular shape and brought into close contact with the inner peripheral surface of the measuring hole.
The underground displacement meter is inserted into the restored sheath pipe that is in close contact with the measurement hole, and the restored sheath pipe is made to follow the displacement in the ground and tunneled by the underground displacement meter. Measure the displacement in front of the face,
A method for measuring forward displacement of a tunnel face, which is characterized by this. The tunnel face forward displacement measurement according to claim 1, wherein a steel pipe is used in which the outer peripheral surface can be expanded in the radial direction by injecting pressurized water into the sheath pipe and the displacement in the ground can be followed in the measurement hole. Method. The tunnel face forward displacement according to claim 1, wherein a resin tube is used in which the outer peripheral surface can be expanded in the radial direction by passing vapor pressure inside the sheath tube and can follow the displacement in the ground in the measurement hole. Measurement method. The invention according to any one of claims 1 to 3, wherein a plurality of segments having an accelerometer built-in are flexibly connected to the underground displacement meter via a flexible joint to employ an ultrafine 3D underground displacement meter. Tunnel face forward displacement measurement method.

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