JP7104637B2 - How to install lock bolts - Google Patents

Description

The present invention relates to a method of constructing a lock bolt.

As shown in FIG. 14, in the construction of a mountain tunnel in which the lock bolt 10 is driven, for example, the ground around the tunnel is pushed out to the inside of the tunnel 500 as shown by an arrow, and the wall surface of the tunnel 500 is deformed. Sometimes. For such a problem, for example, lock bolts such as Patent Document 1 and Patent Document 2 have been proposed.

The lock bolt disclosed in Patent Document 1 is constructed so as to improve the ground with a urethane-based injection material in a region with a large looseness (for example, near the wall surface of a tunnel) while fixing the rock bolt in a stable deep ground. To. On the other hand, Patent Document 2 is configured such that the total length of the lock bolt is greatly extended when the deformation of the ground is larger than expected.

JP-A-2017-150263 Japanese Unexamined Patent Publication No. 2017-186902

However, the lock bolt of Patent Document 1 is intended to improve the ground so that the wall surface of the tunnel is not pushed out, but in the case of a ground where a large deformation occurs so that the pushing does not stop even if the ground improvement is performed. For example, as shown in FIG. 17, a large tensile force may be generated between the deep portion where the lock bolt 10 is fixed and the washer 5, which breaks the lock bolt 10 and eventually causes the lock bolt 10 to break. There is a concern that it will not work.

On the other hand, the lock bolt of Patent Document 2 is prevented from breaking by extending the total length of the lock bolt with respect to the extrusion of the ground, but the structure of the lock bolt is extremely complicated, so that the cost is high. There is a problem. In addition, because the structure of the lock bolt is complicated, for example, the initial elongation of the bolt depends on the adhesion strength between the threads provided on the bolt material and the mortar, and in the process of following the deformation, the mortar is used as the sleeve of the bolt material. It has a structure in which it slides while being crushed by a part, and there is also a problem that it is difficult to control the ground bearing capacity.

The present invention has been made to solve the above problems, and an object of the present invention is to provide a construction method capable of maximizing the function of a lock bolt at a low cost even in a ground where a large deformation may occur. And.

The method for constructing a lock bolt according to the present invention is to form an inflatable tube which is formed in a tubular shape, has an internal space extending in the axial direction, and is plastically deformed and expanded by injecting a pressurized fluid into the internal space. In the step of preparing at least one axially connected lock bolt, the step of forming a plurality of holes in the inner wall surface of the tunnel, and inserting the lock bolt into each of the holes, and in each of the lock bolts. By injecting a pressurized fluid into the internal space at a predetermined water injection pressure or less, each inflatable tube is expanded in the radial direction, and the step of primary fixing to the ground of the tunnel and the displacement of the ground are performed. When the displacement satisfies a predetermined condition, each of the inflatable tubes is expanded in the radial direction by injecting a pressurized fluid into the internal space at a pressure higher than the water injection pressure at each of the lock bolts. It is provided with a step of secondary fixing to the ground of the tunnel.

According to this configuration, the following effects can be obtained. For example, if the lock bolt is firmly fixed to the ground, when the ground is greatly deformed, the lock bolt may be damaged due to excessive tensile force or the screw thread being crushed and the nut falling off. .. On the other hand, in the present invention, the lock bolt having the inflatable tube is expanded in two stages so as to be fixed to the ground. That is, in the primary fixing, the frictional force between the rock bolt and the ground is reduced by suppressing the expansion state of the lock bolt, and as a result, when the ground is deformed to some extent while the deformation of the ground occurs. , The rock bolt is made to follow the large deformation, and the deformation of the ground is allowed little by little. Therefore, it is possible to prevent the lock bolt from being damaged by a large deformation of the ground. Then, when it is determined that the displacement of the ground satisfies the predetermined condition (for example, when the displacement of the ground becomes larger than the reference value or when the displacement converges), the lock bolt is further expanded by further expanding. Secondary fixing is performed so that the frictional force between the lock bolt and the ground becomes large.

As described above, in the present invention, by using a lock bolt having a general-purpose inflatable tube and fixing in two steps, the ground is gradually deformed while holding the ground to some extent in the primary fixing state, and the displacement is allowed. Since it is possible to control the ground support, such as secondary fixing when is converged, or holding the ground with secondary fixing for displacements that exceed the reference value, there is a high possibility of large deformation. The lock bolt can be applied efficiently to the mountain. Therefore, it is possible to maximize the function of the lock bolt at low cost even in the ground where large deformation may occur.

In the above-mentioned rock bolt construction method, the predetermined condition may be appropriately determined based on the state of the ground or the tunnel, and for example, when the displacement of the tunnel becomes larger than the predetermined reference value. Can be done.

Alternatively, the predetermined condition may be when the speed of the displacement becomes equal to or less than a predetermined reference value.

In the method of constructing the lock bolt, the displacement of the ground is not particularly limited, but may be the displacement of at least one reference line connecting any two points in the cross section of the tunnel.

In the method of constructing the lock bolt, each inflatable pipe is provided with at least one recess extending in the axial direction of the outer peripheral surface, and by injecting a pressurized fluid into the internal space, the recess is expanded so as to become smaller. It can be configured so that a part of the recess remains at the time of the secondary fixing.

According to the present invention, it is possible to provide the maximum function of the lock bolt at low cost even in the ground where large deformation can occur, and the amount of initial bolt elongation can be adjusted by the pressurized fluid. It can be easily controlled by the pressure of primary fixing. After the bolt material slides while maintaining a constant load following the deformation of the ground, when the ground is stopped and the ground is supported again, it is only necessary to perform secondary fixing with a pressurized fluid.

It is an exploded perspective view of the lock bolt used in the rock bolt construction method which concerns on one Embodiment of this invention. It is a side view of FIG. It is a side view which shows the construction method of the lock bolt of FIG. It is a side view which shows the construction method of the lock bolt of FIG. It is a side view which shows the construction method of the lock bolt of FIG. It is a block diagram of a water injection system. It is a flowchart which shows the construction method of the lock bolt of FIG. It is sectional drawing of the deformed pipe which shows the construction process of the lock bolt of FIG. It is sectional drawing which shows the construction method of the lock bolt of FIG. It is sectional drawing which shows the construction method of the lock bolt of FIG. It is sectional drawing which shows the construction method of the lock bolt of FIG. It is sectional drawing which shows the construction method of the lock bolt of FIG. It is sectional drawing which shows the example of the reference line of a tunnel. It is sectional drawing which shows the construction method of the tunnel using a lock bolt. It is a perspective view which shows another example of the lock bolt used in this invention. It is sectional drawing which shows the construction method using the lock bolt of FIG. It is sectional drawing of the ground in the construction method of the tunnel using the conventional lock bolt.

Hereinafter, an embodiment of the lock bolt construction method according to the present invention will be described with reference to the drawings. FIG. 1 is an exploded perspective view of a lock bolt used in the construction method of the present embodiment, and FIG. 2 is a side view of FIG. In the following, for convenience of explanation, the back end side of the hole into which the lock bolt is inserted may be referred to as the "tip side" or the "front end side", and the opposite side may be referred to as the "rear end side". Further, the extending direction of the drilled hole and the corresponding extending direction of the lock bolt may be referred to as an axial direction.

<1. Lock bolt structure>
As shown in FIGS. 1 and 2, the lock bolt 10 according to the present embodiment includes a deformed pipe (expandable pipe) 1 formed in a long shape by a steel pipe. A tip sleeve 2 is attached to the tip of the deformed tube 1, and the tip of the deformed tube 1 is closed. On the other hand, a cylindrical rear end sleeve 3 is attached to the rear end of the deformed pipe 1. Further, a water injection adapter 4 for injecting a liquid is detachably attached to the rear portion of the rear end sleeve 3. In addition, a plate-shaped washer 5, a nut 6, and a full screw bolt 7 are prepared in order to drive the lock bolt 10 into the ground. Hereinafter, each member will be described in detail.

The deformed tube 1 is formed as follows. As shown in FIG. 1, first, a hollow cylindrical steel pipe having an internal space 101 is pressed into a plate shape, and then bent in a cylindrical shape with the longitudinal direction as an axial direction to have a recess 102 extending in the axial direction. Is formed in a C-shaped cross section. As the steel pipe, a steel pipe having a wall thickness of about 2 to 4 mm is used so as to be deformed by the pressure of water supplied to the internal space 101 as described later. Further, it is preferable that the steel pipe is made into a plate shape so as not to be completely crushed so that the fluid can flow into the internal space 101 of the steel pipe.

The tip sleeve 2 is composed of a cylindrical fixing portion 21 and a conical tip portion 22 integrally attached so as to close the tip of the fixing portion 21. Then, the tip portion of the deformed pipe 1 described above is inserted into the fixing portion 21 and fixed by welding or the like. In this way, the tip sleeve 2 closes the recess 102 and the internal space 101 at the tip of the deformed tube 1 in a liquid-tight manner.

The rear end sleeve 3 has a fixing portion 31 formed in a cylindrical shape and a cylindrical connecting portion 32 integrally connected to the rear end of the fixing portion 31, and their internal spaces are axially connected. It is formed in a cylindrical shape as a whole so as to communicate with each other. The rear end portion of the deformed pipe 1 is inserted into the fixing portion 31 and is fixed by welding or the like. A female screw 33 is formed on the inner wall surface of the connecting portion 32, and the water injection adapter 4 described below is attached to the female screw 33.

The water injection adapter 4 has a columnar main body portion 41 and a male screw portion 42 fixed to the tip end side of the main body portion 41. The male screw portion 42 is formed to be hollow and is screwed into the female screw of the rear end sleeve 3. A water injection hole 43 is formed on the side surface of the main body 41, and the water injection hole 43 communicates with the internal space of the male screw portion 42. Therefore, the liquid injected from the water injection hole 43 passes through the male screw portion 42 and is injected into the internal space 101 of the deformed pipe 1 via the rear end sleeve 3. Further, a recess 44 for gripping the tool is formed on the outer peripheral surface of the main body 41.

Hereinafter, only the outline of the procedure for constructing the lock bolt 10 will be described, and the construction method will be described in detail later. FIG. 3 is a side view showing a state in which the water injection adapter 4 is attached to the rear end sleeve 3 and the coupling 9 attached to the hose 831 of the pump 83, which will be described later, is attached to the water injection adapter 4. In this state, the lock bolt 10 is inserted into the drilling hole 502. Then, the liquid (water or the like) pumped from the pump 83 is injected from the rear end sleeve 3 into the internal space 101 of the deformed pipe 1 via the hose 831, the coupling 9, and the water injection adapter 4. The details will be described later, but as a result, the deformed pipe expands due to the injected liquid, and the outer peripheral surface of the deformed pipe 1 comes into close contact with the inner wall surface of the drilled hole.

4 and 5 are work diagrams when the lock bolt 10 is fixed to the ground after the water injection is completed. First, as shown in FIG. 4, after discharging the liquid from the internal space 101 of the deformed pipe 1, the water injection adapter 4 is removed from the rear end sleeve 3, and all screw bolts 7 are screwed into the female screw 33 of the rear end sleeve 3. Subsequently, after inserting the through hole of the washer 5 of the all-screw bolt 7, the nut 6 is screwed into the all-screw bolt 7 while the washer 5 is in contact with the ground surface at the periphery of the opening of the drilled hole, and the washer 5 is tightened. In this way, the lock bolt 10 is fixed to the ground.

The lock bolt 10 as described above is known as a lock bolt that can be immediately friction-fixed without waiting for injection of a fixing material such as cement mortar or its hardening, and a general-purpose product can be used.

<2. Overview of water injection system>
Next, the system 8 for injecting a liquid into the lock bolt 10 will be described with reference to FIG. FIG. 6 is a block diagram of the water injection system.

As shown in FIG. 6, the water injection system 8 includes a housing 81, a motor 82 and a pump 83 arranged inside the housing 81, and a control unit 84 that controls the motor 82 and the pump 83. Further, the housing 81 is provided with an operation panel 85 for operating the motor 82 and the pump 83.

The pump 83 is driven by a motor 82 and pumps liquid from a hose 831 connected to the pump 83. The control unit 84 includes a drive control unit 841, a pressure detection unit 842, a time counter 843, and an inverter abnormality detection unit (INV abnormality control unit) 844. The drive control unit 841 controls the output such as the rotation speed of the motor 82. The pressure detection unit 843 detects the pressure of the liquid pumped from the pump 83, and the drive control unit 841 can control the rotation speed of the motor 82 according to the pressure detected by the pressure detection unit 843. ing. Further, the inverter abnormality detection unit 844 detects an operation abnormality of the motor 82.

The operation panel 85 is provided with a status display lamp 851, a pump operation switch 852, a pump stop switch 853, a pressure display unit 854, an operation time display unit 855, and a water injection pressure changeover switch 856. The state of the pump 83 can be visually recognized. For example, when the pump operation switch 852 is pressed, the motor 82 is driven by the control unit 84, and the liquid is pumped from the pump 83. Then, when the pump stop switch 853 is pressed, the driving of the motor 82 is stopped, and the pumping of the liquid by the pump 83 is stopped. The status display lamp 851 is a lamp that indicates the operation and stop of the pump 83. The pressure display unit 854 displays the pressure of the liquid detected by the pressure detection unit 843. The operation time display unit 855 displays the operation time measured by the time counter 842 of the control unit 84. Further, the water injection pressure changeover switch 856 can switch the water injection pressure of the liquid to be pumped into two stages of "low" and "high". This pressure is not particularly limited, but for example, the water injection pressure can be set to 27 MPa at "low" and 32 MPa at "high".

<3. How to install lock bolts>
Next, the method of constructing the lock bolt will be described with reference to FIGS. 7 to 12. FIG. 7 is a flowchart showing a rock bolt construction method, FIG. 8 is a cross-sectional view showing a change in the cross-sectional shape of the deformed pipe during construction, and FIGS. 9 to 12 are cross-sectional views showing rock bolt construction.

First, as shown in FIG. 9, a plurality of drilling holes 502 are formed on the inner wall surface 501 of the tunnel (step S1), and the above-mentioned lock bolt 10 is inserted into each drilling hole 502 (step S2). At this time, the water injection adapter 4 is attached to the rear end sob 3 so that the water injection adapter 4 protrudes from the opening of the drilling hole 502. The cross section of the deformed pipe 1 at this time is as shown in FIG. 8A, and the outer peripheral surface of the deformed pipe 1 is not in close contact with the inner wall surface of the drilled hole 502. Next, as shown in FIG. 10, the hose 831 of the water injection system 8 is connected to the water injection hole 43 of the water injection adapter 4.

Subsequently, after setting the water injection pressure changeover switch 856 of the water injection system 8 to “low” (step S3), the pump operation switch 852 is pressed (step S4). As a result, the low-pressure liquid is pumped from the pump 83, and the liquid is injected into the internal space 101 of the deformed pipe 1. This is referred to as primary water injection pressurization (step S5). As a result, as shown in FIG. 8B, the recess 102 of the deformed tube 1 becomes smaller and the internal space 101 expands. In this way, the outer peripheral surface of the deformed pipe 1 comes into close contact with the inner wall surface of the drilling 502 and presses it. Then, the liquid is continuously pumped until the water injection pressure exceeds a predetermined value (NO in step S6), and when the set value is exceeded (YES in step S6), the drive control unit 841 stops the rotation of the motor 82 and the pump 83. Water injection from is stopped. Therefore, the operator presses the pump stop switch 853 to stop the expansion work of the lock bolt 10. Hereinafter, this state will be referred to as primary expansion. In the primary expansion, the deformed tube 1 is not completely expanded, and is further expanded by the secondary expansion described later.

Next, the water injection adapter 4 is removed from the rear end sleeve 3, and the liquid in the deformed pipe 1 is discharged. Subsequently, as shown in FIGS. 4 and 5, the nut 6 is screwed into the all-screw bolt 7 and the washer 5 is tightened. In this way, the lock bolt 10 is fixed to the ground, and the primary fixing is completed (step S7). In the primary fixing, the frictional force between the lock bolt 10 and the ground is reduced by suppressing the expansion state of the lock bolt 10, whereby the rock bolt 10 is greatly deformed while suppressing the deformation of the ground to some extent. It is possible to allow the ground deformation little by little by moving it according to.

By the way, in the tunnel excavation work, the measurement work in the tunnel 500 is always performed, and in the present invention, the cross-section measurement result is used at the timing of the primary fixing and the secondary fixing of the lock bolt 50. For example, as shown in FIG. 13A, parallel reference lines A and B extending horizontally near the bottom wall 503 of the tunnel 500 and above the bottom wall 503 are defined, and the lengths of these reference lines A and B are measured. .. Both ends of the reference lines A and B are positions in contact with the inner wall surface 501 of the tunnel 500. That is, the lengths of the reference lines A and B are the lengths in the width direction of the tunnel 500. Alternatively, as shown in FIG. 13B, diagonal reference lines C and D connecting both ends of the reference line B and the uppermost portion of the tunnel inner wall surface 501 are defined, and their lengths are measured.

In this way, a part of the shape of the internal space of the tunnel 500 immediately after the lock bolt 10 is placed is measured, and this is used as the initial value. However, the reference lines A to D described above are examples, and other dimensions can be measured as long as the length of the portion is suitable for measuring the displacement of the tunnel 500. Further, the time for measuring the reference lines A to D may be before the construction of the lock bolt 10.

Subsequently, after the lock bolt 10 is first fixed, the reference lines A to D are measured over time, and when the displacement from the initial value exceeds the reference value (YES in step S8), the displacement of the ground is increased. Assuming that the size has increased, the lock bolt 10 is secondarily expanded.

The determination of the displacement at this time is not particularly limited, but for example, in the case of adopting FIG. 13A, when any of the reference lines A and B exceeds the reference value, FIG. 13B is shown. When adopted, the secondary expansion can be performed when any of the reference lines A to D exceeds the reference value. The reference value can be appropriately determined depending on the condition of the tunnel 500 and the ground, but can be, for example, 90 mm (when a displacement of 90 mm occurs with respect to the initial value).

When the displacement of the tunnel 500 exceeds the reference value in this way, for example, as shown in FIG. 11, the ground presses the washer 5, and at this time, the lock bolt 10 is a friction fixing type that is not fixed by the fixing material. Therefore, it is considered that the lock bolt 10 follows the displacement without restraining the ground, and the ground deformation is allowed by that amount, and the internal space of the tunnel 500 is narrowed. Therefore, secondary water injection is performed to secondarily expand the lock bolt 10.

To perform the secondary expansion, the washer 5, the nut 6, and the full screw bolt 7 are removed from the lock bolt 10, and then the water injection adapter 4 is attached to the rear end sleeve 3. Then, as shown in FIG. 12, the hose 831 of the pump 83 is connected to the water injection adapter 4 via the coupling 9 to inject water (step S10). At this time, after setting the water injection pressure changeover switch 856 of the water injection system 8 to “high” (step S11), the pump operation switch 852 is pressed (step S12). As a result, a high-pressure liquid is pumped from the pump 83, and the liquid is injected into the internal space 101 of the deformed pipe 1. This will be referred to as secondary water injection pressurization (step S13). As a result, the internal space 101 of the deformed pipe 1 further expands, the recess 102 becomes smaller as shown in FIG. 8C, and the outer peripheral surface of the deformed pipe 1 further presses the inner wall surface of the drilled hole 502. In this way, the lock bolt 10 is firmly fixed to the inner wall surface of the drilled hole.

Then, the liquid is continuously pumped until the water injection pressure exceeds the set value (NO in step S14), and when the set value is exceeded (YES in step S14), the drive control unit 841 stops the rotation of the motor 82 and the pump 83. Stop water injection from. Then, in the same manner as described above, the water injection adapter 4 is removed, and all screw bolts 7 are attached to the rear end sleeve 3. Then, after inserting all the screw bolts 7 into the washer 5, the washer 5 is tightened with the nut 6, and the lock bolt 10 is fixed to the ground to complete the secondary fixing (step S15).

It should be noted that the judgment for performing the secondary fixing is not when the displacement of the ground exceeds the reference value (NO in step S8) as described above, but when it is judged that the displacement of the ground has converged (NO). Secondary fixing is also performed in YES) of step S9. For example, when the displacement speed of the reference lines A to D is within 1 to 3 mm / month, it is assumed that the displacement of the ground has converged, and secondary fixing is performed. However, the judgment of the convergence of the displacement of the ground is not limited to this.

<3. Features>
As described above, according to the present embodiment, the lock bolt 10 is expanded in two stages so as to be fixed to the ground. That is, in the primary expansion, the frictional force between the lock bolt 10 and the ground is reduced by suppressing the expanded state of the lock bolt 10. As a result, the deformation of the ground is allowed little by little while suppressing the deformation of the ground to some extent. Therefore, for example, as shown in FIG. 11, even if the ground is greatly deformed, it is possible to prevent the lock bolt 10 from being damaged due to an excessive tensile force or a crushed screw thread and the nut falling off. can. When it is determined that the displacement of the ground satisfies the predetermined condition, the lock bolt 10 is secondarily expanded so that the frictional force between the lock bolt 10 and the ground is maximized. Therefore, in the primary fixing state, the deformation of the ground is allowed to some extent, and when the displacement converges, the ground is secondarily fixed, or when the displacement exceeds the standard value, the ground can be held down by the secondary fixing. Since the ground support can be controlled, the lock bolt 10 will not be broken even in the ground where a large deformation occurs.

In the above construction method, a general-purpose inflatable lock bolt can be used instead of using a special lock bolt. Therefore, it is possible to maximize the function of the lock bolt 10 at low cost even in the ground where large deformation may occur.

<4. Modification example>
Although the embodiments of the present invention have been described above, the present invention is not limited to the above embodiments, and various modifications can be made without departing from the spirit of the present invention.

The lock bolt shown in the above embodiment is an example, and the inflatable tube according to the present invention is not limited to this, and various aspects are possible. That is, it is not particularly limited as long as it is an inflatable pipe that can be expanded in at least two stages by injecting a liquid and can be brought into close contact with the inner wall surface of the drilled hole. For example, in the above embodiment, the deformed tube 1 is formed with only one recess 102 extending in the axial direction, but the structure of the deformed tube 1 is not particularly limited. For example, it may be a deformed tube having recesses formed at two or more places. Further, the configurations of the front end sleeve 2, the rear end sleeve 3, the water injection adapter 4, and the like are not particularly limited.

In the above embodiment, the lock bolt 10 is composed of one deformed pipe 1, but a plurality of deformed pipes 1 may be connected in the axial direction via a connecting sleeve. In this case, if the connecting sleeve is hollow and the liquid can flow in the adjacent deformed pipe 1, when the liquid is pumped from the terminal deformed pipe 1, all the connected deformed pipes 1 are connected. Can be inflated.

Further, as shown in FIG. 15, the lock bolt 10 may be provided with a hollow male threaded sleeve 3'instead of the rear end sleeve 3 provided with the female thread 33. The hollow male threaded sleeve 3'provides a male threaded portion 35 having a screw diameter equivalent to that of the full threaded bolt 7, the inside of the male threaded portion 35 becomes a hollow portion 36, and the hollow portion 36 communicates with the internal space 101 of the deformed pipe 1. ing.

A female screw type water injection adapter 4'can be screwed into the hollow male threaded sleeve 3', and the water injection hole 44 of the water injection adapter 4'communicates with the hollow portion 36 and connects the coupling 9 to the deformed pipe 1. Water can be injected into the internal space 101.

The lock bolt 10 provided with the hollow male threaded sleeve 3'can perform water injection expansion work with the washer 5 and the nut 6 fitted.

That is, in the ground where a large deformation occurs after the primary fixing of the lock bolt, as shown in FIG. 16, the washer 5 pressed by the nut 6 supports the pushing force from the ground. Removing the nut 6 and washer 5 for the next expansion work is not good in workability. Therefore, if the lock bolt is equipped with a sleeve 3'with a hollow male screw, the water injection adapter 4'is fitted for the secondary expansion work with the nut 6 and the washer 5 fitted, and the deformed pipe 1 is secondarily expanded. It is safe and easy to install because it can be made to work.

Further, the water injection system 8 described above is an example, and is not particularly limited as long as the liquid can be pumped so that the lock bolt 10 can be expanded in at least two steps.

In the above embodiment, the secondary fixing is started when the displacement of the ground exceeds the reference value or when it is determined that the displacement of the ground has converged. Such secondary fixing is started. The requirement for this is "when the predetermined conditions are satisfied" according to the present invention. However, this predetermined condition can be appropriately changed depending on the mode of the tunnel or the lock bolt.

1: Deformed pipe 10: Lock bolt 101: Internal space 500: Tunnel 502: Drilling

Claims (5)

A lock bolt that is formed in a cylindrical shape and has an internal space extending in the axial direction, and at least one inflatable tube that is plastically deformed and expanded by injecting a pressurized fluid into the internal space is connected in the axial direction. Steps to prepare and
A step of forming a plurality of holes on the inner wall surface of the tunnel and inserting the lock bolt into each hole,
In each of the lock bolts, a step of injecting a pressurized fluid into the internal space at a predetermined water injection pressure or less to expand each of the inflatable pipes in the radial direction and temporarily fix the inflatable pipe to the ground of the tunnel.
When the displacement of the ground is measured and the displacement satisfies a predetermined condition, the expansion type is performed by injecting a pressurized fluid into the internal space at a pressure higher than the water injection pressure at each lock bolt. The step of expanding the pipe in the radial direction and secondary fixing it to the ground of the tunnel,
How to install lock bolts. The method for constructing a lock bolt according to claim 1, wherein the predetermined condition is when the displacement becomes larger than a predetermined reference value. The method for constructing a lock bolt according to claim 1, wherein the predetermined condition is when the speed of the displacement becomes equal to or less than a predetermined reference value. The method for constructing a lock bolt according to any one of claims 1 to 3, wherein the displacement of the ground is the displacement of at least one reference line connecting any two points in the cross section of the tunnel. Each inflatable tube is provided with at least one recess extending in the axial direction of the outer peripheral surface, and is configured to expand so that the recess becomes smaller by injecting a pressurized fluid into the internal space.
The method for constructing a lock bolt according to any one of claims 1 to 4, wherein a part of the concave portion remains at the time of the secondary fixing.

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