JP2006003324A - Method of measuring distribution of axial force of lock bolt and method of measuring distribution of axial force of lock bolt and the lock bolt - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide the method of measuring distribution of axial force of a lock bolt which is needless of wiring for a strain gauge accordingly, simple in management and moreover capable of surely measuring the axial force, and to provide the lock bolt. <P>SOLUTION: At the time of execution of the solid lock bolt 10, previously the ultrasound measurement is performed in such a way that from the exposed part of the lock bolt 10 i.e. the incident part 11 the ultrasound is transmitted and received for obtaining the receiving time difference between the reference points. Afterward, the ultrasound measurement is performed again and the axial force is calculated from the change of the receiving time difference. The lock bolt is provided with reference points between the incident part 11 and end part 12 for reflecting the ultrasound. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a lock bolt axial force distribution measuring method for measuring an axial force of a lock bolt used in a ground improvement method such as a natom method, and a lock bolt used therefor.

  As a rock bolt axial force distribution measuring method, for example, the inventions described in Patent Documents 1 and 2 are known. In the invention described in Patent Document 1, a measurement groove is provided in an axial force measuring meter made of a deformed steel bar lock bolt, a strain gauge is attached to the bottom surface, and a lead wire is provided in the measurement groove. In the invention described in Patent Document 2, a strain gauge is affixed to the surface of the steel pipe expansion type lock bolt, and the strain gauge and the input / output cable are protected by a protective pipe, a filler, and the like.

  In any of the prior inventions, the axial force is measured using a strain gauge, and a cable must be arranged up to the measuring section. The handling at the tunnel site is complicated and expensive as a measuring meter. It was.

In addition, although it is a reference example that is completely different from the technical field of the lock bolt, a bolt axial force measurement method using ultrasonic waves is known as described in Patent Document 3. The invention determines the ratio of the propagation time of longitudinal and transverse waves in the axial direction, and is concluded from the relationship between the ratio of propagation time of longitudinal and transverse waves obtained in advance under a known axial force and the tensile stress in the axial direction. The bolt axial force of the entire bolt is obtained. Therefore, there is no suggestion of applying to a rock bolt, and no disclosure about the feasibility at the time of application.
4-38541 JP 2004-37227 A JP-A-5-203513

  In view of such a conventional situation, an object of the present invention is to provide a lock bolt axial force distribution measuring method and a lock bolt that can be easily managed and can reliably measure an axial force.

  In order to achieve the above object, a feature of the lock bolt axial force distribution measuring method according to the present invention is a lock bolt axial force distribution measuring method for measuring an axial force acting on a hollow lock bolt, wherein the construction of the lock bolt is performed. Sometimes ultrasonic waves are transmitted and received in advance from the incident part, which is the exposed part of the rock bolt, and the ultrasonic measurement is performed to obtain the difference in the reception time of the target point, and later the ultrasonic measurement is performed again due to the change in the reception time difference. It is to calculate the axial force.

  According to the same feature, the axial force can be calculated from the change in the reception time difference of the ultrasonic wave at each gauge point without using a strain gauge.

  Moreover, you may provide the mark which reflects an ultrasonic wave between the said incident part and termination | terminus of the ultrasonic wave in a rock bolt, and it is desirable for each mark to contain a notch.

  Furthermore, when the ultrasonic wave is a transverse wave, it is desirable that the incident portion of the lock bolt is inclined with respect to the longitudinal direction of the lock bolt.

  On the other hand, the feature of the lock bolt that can be used in the method for measuring the axial force distribution of the lock bolt is that the ultrasonic wave incident portion is inclined with respect to the longitudinal direction of the lock bolt when the ultrasonic wave is a transverse wave. There is. Further, the lock bolt desirably has a plurality of notches as the mark.

  According to the characteristics of the rock bolt axial force distribution measuring method according to the present invention described above, the use of ultrasonic waves eliminates the need for strain gauge wiring and the like, simplifies management, and allows the axial force to be reliably measured. To provide a rock bolt axial force distribution measuring method and a lock bolt.

  Other objects, configurations, and effects of the present invention will become apparent from the following embodiments of the present invention.

  Next, the present invention will be described in more detail with reference to the accompanying drawings as appropriate. FIG. 1 shows a lock bolt 10 and an axial force distribution measuring device 1 used for measuring an axial force distribution according to the present invention. The axial force distribution measuring apparatus 1 includes a probe 2 that transmits / receives ultrasonic waves to / from the rock bolt 10, a pulsar / receiver 3 that transmits / receives ultrasonic waves, and a PC (that controls and displays received signals). A personal computer 4 and a monitor 5 are provided.

  The lock bolt 10 is formed by welding a water injection side sleeve 30 and a sealing side sleeve 40 to both ends of the deformed pipe 20. As shown in FIG. 2, the deformed pipe 20 is formed by flattening a hot-dip plated steel pipe and forming a substantially C shape, and the degree of flatness is different at each cross-sectional position. As shown in FIGS. 2B and 2C, the pipe outer surface 21 and the pipe inner surface 22 are close to each other at the end of the entire length. At the position shown in FIG. ing. When water is injected into the pipe interior 23, the pipe inner surface 22 becomes enormous as shown in FIG.

  The distal end of the substantially C-shaped deformed pipe 20 is inserted into the hole of the water injection side sleeve 30, and is fixed to the water injection side sleeve 30 by the welded portion 24 at the front end portion thereof. The other end of the deformed tube 20 is also welded to the sealing sleeve 40 in the same manner. A water injection hole 27 is formed through the sleeve side portion 32 and the pipe outer surface 21 of the water injection side sleeve 30, and water is supplied from the outside to the pipe interior 23 through the water injection hole 27.

  As shown in FIG. 3, the sleeve tip 31 of the water injection side sleeve 30 is cut obliquely at a notch 33, and forms a slope 34 that becomes the ultrasonic incident portion 11 together with a part of the welded portion 24. The probe 2 comes into contact with the slope 34 and ultrasonic waves are transmitted and received toward the deformed tube 20. The inclined surface 34 is inclined by about 45 degrees with respect to the entire axis of the deformed tube 20, and a transverse wave ultrasonic wave is transmitted from the probe 2. It is convenient for machining to cut the sleeve tip 31 so as to become deeper as the distance from the center becomes larger at the notch 33. In addition, when making a longitudinal wave enter, it is good to cut a part flatly as shown in FIG. 5, and to make the probe 2 contact a flat surface.

  As shown in FIGS. 4A and 4B, a plurality of notches N1-5 are formed as reference points at appropriate portions of the deformed tube 20. Each notch N1-5 is provided in a possible range so as to be along the peripheral portion of the lock bolt 10, and is arranged at the same phase in different longitudinal positions. In addition, each notch N1-5 may be arrange | positioned so that a phase may differ in a different longitudinal direction position like FIG.4 (c), In this case, an ultrasonic wave is notch N1-5 of the intermediate part, and the edge part 12. Things can be detected more reliably. Note that only one of the signals of the end notch N5 and the end 12 may be used.

  By the way, when a material having a similar acoustic impedance to the material of the deformed tube 20 enters each notch N1-5, the reflected signal from each notch N1-5 may be reduced. Therefore, as shown in FIG. 4D, each notch N1-5 has an insert 16 made of a material having a low acoustic wave propagation rate, such as a material having a different acoustic impedance from the material of the deformed tube 20, such as a synthetic resin. May be inserted inside each notch N1-5 by filling or the like.

  According to the experiment, especially when a transverse wave is incident, it is confirmed that if there are many irregularities on the surface, the attenuation of the ultrasonic wave is larger than when the surface is smooth. It is flat enough not to affect the reflection of ultrasonic waves. The mark may be a recess or a protrusion other than the notch, but the notch can most clearly detect the reflection of the ultrasonic wave.

  At the time of installation, the lock bolt 10 is inserted into the insertion hole 101 formed at an appropriate location on the tunnel wall 100. At the time of insertion, a gap 103 remains between the insertion hole 101 and the deformed tube 20 as shown in FIG. Thereafter, a seal head is attached to the water injection side sleeve 30, and water is pressurized and injected from the water injection hole 27 into the pipe interior 23. Due to this water injection, the deformed tube 20 expands as shown by the alternate long and short dash line 20 'in FIG. 1 and FIG. Acts to complete the fixing of the lock bolt 10 to the insertion hole 101. A bearing plate 15 is inserted in the vicinity of the water injection side sleeve 30 to substantially support the tunnel wall 100.

  At the time of measurement, the probe 2 is brought into contact with the inclined surface 34 (incident part 11) through a contact medium as shown in FIG. 3, and ultrasonic waves are incident and received. In the case of FIG. 5, the probe 2 is brought into contact with the flat incident portion 11.

First, the propagation time T _i (i is the section number) is obtained from the difference between the transmission time of the ultrasonic wave and the reception time of the reflected wave reflected from each of the reference points (N1-5) shown in FIG. Next, the section propagation time can be calculated from the difference T _i −T _{i−1 in} the propagation time between adjacent sections. Based on the above procedure, the section propagation times of the respective mark sections SC1 to SC5 are measured as initial values immediately after the rock bolt is placed. Each section propagation time is similarly measured at any time after placement, and a change rate (section propagation time change rate dD) with respect to the initial value is obtained. The axial force of each section can be calculated from the correlation between the axial force obtained in advance and the section propagation time change rate dD.

  According to the experiments by the inventors, it has been found that the axial force F caused by extending the steel specimen and the propagation time change rate dD corresponding to the degree of extension between the gauge points have a certain correlation. In the case of a transverse wave, the axial force F and the propagation time change rate dD are substantially proportional, and in the case of a longitudinal wave, these proportional coefficients dD / F are larger than those in the case of a transverse wave. In addition to the extension of the test body due to the axial force F, the influence that the propagation speed of the ultrasonic wave decreases due to the axial force F is integrated. And it was confirmed by experiment that the axial force F of the lock bolt 10 can be substantially obtained by using these correlations and the measured propagation time change rate dD. Further, in the case of the transverse wave shown in FIG. 3, the reflected wave detection is better in the frequency region of about 1 MHz to 2 MHz, but in the case of the longitudinal wave shown in FIG. 5, the reflected wave detection is better in the frequency region of about 5 MHz. Turned out to be.

Next, still another embodiment of the present invention will be described.
In the above embodiment, the hollow steel pipe expansion type rock bolt 10 is used. However, as the lock bolt, for example, a self-piercing lock bolt 51 (10) whose cross section is shown in FIG. 6 may be used. This self-drilling lock bolt 51 has a bit 53 for excavating a hole at the tip of a rod 52 that forms a tube through which compressed water passes in the center. The tunnel wall 100 is inserted into the tunnel wall 100 while self-drilling. Such a rod 52 may be provided with the above-mentioned mark. Since a thread groove is formed on the surface of the rod 52, it is more preferable to measure using a longitudinal wave.

  Moreover, in the said embodiment, the lock bolt 10 which welded the water injection side sleeve 30 and the sealing side sleeve 40 to the both ends of the deformed pipe 20 was used. However, as shown in FIG. 7, the lock bolt is cut after being fixed in a state where the water injection side sleeve 30 is protruded, and the probe 2 is brought into contact with the cut end 11 of the deformed tube 20 to act on the lock bolt. Axial force may be measured.

  In the above-described embodiment, the notch N1-5 is formed in the deformed pipe 20 as five marks. However, the number of reference points is not limited to five, and can be arbitrarily set.

  In the above embodiment, the present invention is expressed as a method for measuring the axial force distribution of a rock bolt, but the present invention can also be expressed as a method for measuring an extension distribution of a lock bolt.

  INDUSTRIAL APPLICABILITY The present invention can be used as a rock bolt axial force distribution measuring method for measuring the axial force of a lock bolt used in a so-called natom method that is a kind of tunnel construction method. It can also be used in a method for measuring the axial force distribution of rock bolts for ground improvement other than tunnels.

It is a crush figure of a rock bolt, and a block diagram of an axial force distribution measuring device. FIG. 2 is a cross-sectional view of the lock bolt in FIG. 1, where (a) is a view in the A direction, (b) is a cross-sectional view along BB, (c) is a cross-sectional view along CC, and (d) is a cross-sectional view along DD. (E) is DD sectional drawing after expansion | swelling. It is a crushing figure of the head of a lock bolt. (A) is a sectional view in a plane perpendicular to the bolt axial direction showing the relationship between the lock bolt and the notch, (b) is a diagram showing the notch position in the entire length of the lock bolt, and (c) is a diagram showing the relationship between the lock bolt and the notch. (A) Equivalent figure which shows another relationship, (d) is sectional drawing along the volt | bolt axial direction which shows the relationship between a lock bolt and a notch. It is a head fragmentary figure which shows another embodiment of a rock bolt. It is sectional drawing which shows another embodiment of a rock bolt. It is a crush figure which shows another embodiment of a rock bolt, and a block diagram of an axial force distribution measuring device.

Explanation of symbols

1: Axial force distribution measuring device, 2: probe, 3: pulser / receiver, 4: PC, 5: monitor, 10: lock bolt, 11: incident part, 12: end, 15: bearing plate, 16: Insert, 20, 20 ′: Deformed pipe, 21: Pipe outer surface, 22: Pipe inner surface, 23: Pipe inside, 24: Welded part, 25: Opening part, 26: Center part, 27: Water injection hole, 30: Water injection side Sleeve: 31: Sleeve tip, 32: Sleeve side, 33: Notch, 34: Slope, 40: Sealing sleeve, 51: Self-drilling lock bolt, 52: Rod, 53: Bit, 100: Tunnel wall, 101 : Insertion hole, 103: gap, N1-5: gauge point (notch), SC1-5: gauge section, Da: propagation time, Db: section propagation time, dD: propagation time change rate

Claims (6)

A lock bolt axial force distribution measuring method for measuring an axial force acting on a hollow lock bolt (10), wherein an ultrasonic wave is transmitted in advance from an incident portion (11) which is an exposed portion of the lock bolt when the lock bolt is applied. Then, an ultrasonic measurement is performed to obtain a difference in reception time of the target by receiving, and after that, the ultrasonic measurement is performed again to calculate the axial force according to a change in the reception time difference. Measurement method. The rock bolt axial force distribution measuring method according to claim 1, wherein a gauge point for reflecting the ultrasonic wave is provided between the incident part (11) and the terminal end (12) of the ultrasonic wave in the rock bolt. The rock bolt axial force distribution measuring method according to claim 1 or 2, wherein the mark includes a notch. The lock bolt according to any one of claims 1 to 3, wherein the ultrasonic wave is a transverse wave, and an incident portion (11, 34) of the lock bolt is inclined with respect to a longitudinal direction of the lock bolt. Axial force distribution measurement method. It is a lock bolt which can be used for the rock bolt axial force distribution measuring method in any one of Claims 1-4, Comprising: The said ultrasonic incident part (11) inclines with respect to the longitudinal direction of a lock bolt. A rock bolt characterized by It is a lock bolt which can be used for the lock bolt axial force distribution measuring method in any one of Claims 1-4, Comprising: It has a some notch as the said mark, The lock bolt characterized by the above-mentioned.

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