JP4834458B2 - Ultrasonic axial force measurement lock bolt and lock bolt axial force measurement method - Google Patents

Description

  The present invention relates to a steel pipe expansion type ultrasonic axial force measurement lock bolt and a lock bolt axial force measurement method.

As lock bolts used for tunnel construction by a conventional so-called NATM construction method, those described in the following Patent Documents 1 and 2 are known. Further, as lock bolts capable of measuring axial force using ultrasonic waves, those described in Patent Documents 3 and 4 are known.
4-38541 JP 2004-37227 A JP 2006-3323 A JP 2006-3324 A

  However, since the one described in Patent Document 1 requires time until the mortar is cured, it is impossible to measure immediately, and the one described in Patent Document 2 is difficult to measure the detailed axial force distribution, In both cases, wiring was required and measurement was time consuming and expensive. As a result, it has been implemented only for B measurement used in a scattered manner on a partial cross section of the tunnel, and has not been applied to monitoring of a tunnel by A measurement as daily management. In addition, in all of Patent Documents 3 and 4, ultrasonic measurement cannot always be performed smoothly.

  In view of such a conventional situation, an object of the present invention is to provide an ultrasonic axial force measurement lock bolt and a lock bolt axial force measurement method capable of easily and accurately measuring an axial force.

In order to achieve the above object, the steel tube expansion type ultrasonic axial force measurement lock bolt according to the present invention has two or more axial force measurement lock bolts having an expandable steel pipe and a target for ultrasonic reflection. A measuring bar, and a notch group is formed on each of the measuring bars, and a position of the notch group between one measuring bar and another measuring bar in the longitudinal direction of the measuring bar is different.
According to the same feature, for example, the signal on the near side and the back side are received by being shared by the respective measuring rods, whereby attenuation of the signal can be prevented more efficiently.

  The degree of notch in the measuring rod may be increased toward the end of the measuring rod. According to the same feature, it compensates for the attenuation of reflected ultrasonic waves, which are significantly attenuated at the terminal side opposite to the ultrasonic wave incident side, and makes the received signal intensity that is originally different depending on the notch formation position as uniform as possible. The possibility of a single measurement can be expanded.

  Here, desirably, the degree of the notch is a notch area ratio which is a ratio of the area of the vertical wall portion of the notch to the total cross-sectional area in a cross section orthogonal to the longitudinal direction of the measuring rod.

Furthermore, in addition to the above features, the measuring rod may be covered with at least a rust-proof coating. This prevents signal attenuation due to rusting and enables accurate monitoring.
Further, the degree of notch in the measuring rod is set to the end of the measuring rod so that the amplitude y of the reflected signal according to the following equation (1) determined by the distance x from the incident portion of the measuring rod to each notch becomes a measurable value. The side may be enlarged.
y = exp (cx + d) (1)
However, c and d are constants.

On the other hand, the feature of the lock bolt axial force measurement method for measuring the axial force acting on the lock bolt described in each of the above features is that there are two axial force measurement methods having an expandable steel pipe and a target for ultrasonic reflection. More than one measuring rod, each having a notch group formed on the measuring rod, and the amplitude y of the reflected signal according to the following equation (1) determined by the distance x from the incident portion of the measuring rod to each notch The purpose is to increase the degree of notch in the measuring rod toward the end side of the measuring rod so that the value can be measured even at the end side of the measuring rod.
y = exp (cx + d) (1)
However, c and d are constants.

In addition, another feature of the lock bolt axial force measuring method for measuring the axial force acting on the lock bolt described in the above feature is that there are two axial force measuring instruments having an expandable steel pipe and a target for ultrasonic reflection. The measuring rod is provided with a notch group formed on the measuring rod, and an ultrasonic wave is transmitted in advance from the incident portion which is an exposed portion of the measuring rod and reflected from the gauge point when the lock bolt is applied. An ultrasonic measurement is performed in which a wave is received to obtain a reception time difference of a reflected wave from a gage, and the ultrasonic measurement is performed again later to calculate the axial force based on a change in the reception time difference.

  According to the characteristics of the ultrasonic axial force measurement lock bolt and the lock bolt axial force measurement method according to the present invention described above, the amplitudes of the received signals that are different at the notch formation position are made more uniform, or the measurement rod is selected according to the reception position. This makes it possible to improve the signal strength and easily and accurately measure the axial force.

  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 steel pipe expansion type rock bolt 10 and an axial force measuring device 1 used for measuring an axial force of the present invention. The axial force measuring apparatus 1 includes a probe 2 that transmits / receives ultrasonic waves to / from the rock bolt 10, a pulser / receiver 3 that transmits / receives ultrasonic waves, and a PC (personal computer) that controls signals and processes / displays received signals. Computer) 4 and a monitor 5.

  The lock bolt 10 is welded or welded (hereinafter referred to as “welding”) to the water injection side sleeve 30 and the sealing side sleeve 40 at both ends of the deformed pipe 20 that is a tubular body, and is further disposed in the deformed pipe 20. The measuring rod 50 is provided. 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 flatness is different at each cross-sectional position near the end of the lock bolt 10. The bent outer surface 21 and the bent inner surface 22 are close to each other at the end of the entire length, and at the position shown in FIG. When water is poured into the pipe interior 23, the bent inner surface 22 becomes enormous as shown in FIG.

  The measuring rod 50 is made of steel or aluminum, and passes through the centers of the water injection side sleeve 30 and the sealing side sleeve 40 and is disposed in the recess 26 of the deformed pipe 20 as shown in FIG. It is fixed in the water injection side sleeve 30 and the sealing side sleeve 40 through 59. The outer edge of the ring-shaped spacer 59 is fixed by a welded portion 58h.

  When both ends or a part of the measuring rod 50 are fixed to a deformed tube or sleeve of a lock bolt by welding or the like, measurement is performed including the portion not fixed by the pressing force against the drilling hole 101 of the tube body 20. The substantially entire length of the rod 50 is effectively integrated with the tube body 20.

  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 a weld at the front end portion. The other end of the deformed tube 20 is also welded to the sealing sleeve 40 in the same manner. A water injection hole 34 is formed through the side portion of the water injection side sleeve 30 and the bent outer surface 21, and water is supplied from the outside to the pipe interior 23 through the water injection hole 34.

  The measuring rod 50 in the water injection side sleeve 30 has a start end surface 51 which is the incident side protrudes from the outer end 59x of the water injection side sleeve 30 so that ultrasonic waves can enter the measurement rod 50. The ring-shaped spacer 59 is fixed to the measuring rod 50 by the welded portion 58h.

  On the other hand, the measuring rod 50 in the sealing-side sleeve 40 is fixed to the ring-shaped spacer 59 by tightening and fixing means 58x including a threaded portion 58j and a nut 58k provided at the end. The tightening and fixing means 58x inherently attenuates the incident ultrasonic wave and causes noise. However, even if it is sufficiently separated from the starting end face 51 that becomes the incident portion 11 and is fixed by the fastening fixing means 58x in the sealing side sleeve 40, the noise becomes relatively small. Therefore, the influence of noise can be eliminated and the mounting workability of the measuring rod 50 can be improved. The fastening means 58x is not limited to the threaded portion 58j and the nut 58k, and various means such as a latch means can be used. By releasing these, the measuring rod 50 can be attached to and detached from the deformed tube 20. .

As shown in FIGS. 3 (a) and 3 (b), a plurality of notches 55 (N1-5) are formed as reference points at appropriate portions of the measuring rod 50. Each notch N1-5 is a groove continuously cut at the same depth t in the circumferential direction at each notch position of the measuring rod 50, and the vertical wall portion 55 extends in a direction perpendicular to the longitudinal direction. Stand out. Therefore, as shown in FIG. 3 (c), the area of the portion where the vertical wall portion 56 is projected onto the cross section perpendicular to the longitudinal direction of the measuring rod at each notch position (the outer circle of the measuring rod 50 and the N1-5 The notch area Za which is the area between the outer circles) is in the relationship of the following equation (2) between the depth t and the radius r of the measuring rod.
Za = π (2rt−t ² ) (2)

The width W of each groove does not significantly affect signal reflection. Moreover, the cross-sectional area Z in the cross section orthogonal to the longitudinal direction of the measuring rod 50 is πr ² . Therefore, the notch area ratio that is the area ratio of the notch area Za to the total cross-sectional area Z is Za / Z.

  When the notch area Za at each position is made constant, the signal intensity attenuates as shown by the attenuation line f1 in FIG. 4 and reaches the measurement limit level (Pm) earlier, and further measurement at the end side position becomes impossible. Further, as shown in FIG. 5A, it is difficult to specify W3 when the signal reception sensitivity is matched to W1 on the front side (incident side), and when it is matched to W2 and W3 as shown in FIGS. The signal before the count is saturated, making measurement difficult.

By the way, if the distance from the incident end to the notch is x and the amplitude of the received ultrasonic wave is y, the attenuation line can be expressed exponentially,
y = exp (ax + b) (3)
It becomes. However, a and b are constants.

Therefore, first, as shown by the attenuation line f2 in FIG. 4B, the notch depth t is formed deeper toward the end of the measuring rod and the notch area Za is expanded, so that the measurement limit level can be obtained even at a farther point N5. (Pm) can be received, and as shown in FIG. 5D, the level of the signal received at the start end face 51 can be adjusted to be substantially the same between the notches N1-5. . In particular, when the above equation (3) is taken into consideration, the amplitude y of the reflected signal according to the following equation (1) determined by the distance x from the incident portion of the measuring rod to each notch is a value that can be measured even on the end side of the measuring rod. The degree of the notch in the measuring rod, that is, the notch area ratio Za / Z may be increased toward the end side of the measuring rod so that
y = exp (cx + d) (1)
However, c and d are constants.

  By the way, when many irregularities exist on the surface, it was confirmed by experiments that the attenuation of the ultrasonic wave was severe. Therefore, the surface of the measuring rod 50 was flat except for the notch. Further, according to experiments by the inventors, it has been found that the reflected signal intensity from the notch is proportional to the notch area Za regardless of the shape of the notch, and is not necessarily proportional only to the depth of the notch.

  Further, as shown in FIG. 6, each notch 55 (N1 to N5) has a vertical wall portion 56 formed by cutting in a direction orthogonal to the longitudinal direction of the measuring rod 50 and a taper with respect to the vertical wall portion 56. You may form from the flat part 57 shaved in the shape. A portion Sa of the ultrasonic wave incident from the start end surface 51 that is the incident portion 11 is significantly reflected by the vertical wall portion 56, while the reflected wave Sb reflected by the end surface 52 is reflected by the flat portion 57. Since the light passes through the cutouts N1 to N5 without being largely reflected, the reflected waves from the cutouts N1-5 and the end face 52 in the intermediate portion can be reliably detected. Therefore, the cutout area ratio Za / Z may be calculated at the vertical wall portion 56 on the incident side. In addition to the notch, the mark may be a recess or a protrusion, but when a notch having a vertical portion is provided, reflection of ultrasonic waves can be detected most clearly.

  At the time of installation, the lock bolt 10 is inserted into an insertion hole 101 formed at an appropriate location on the tunnel outer 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. By this water injection, the deformed tube 20 expands as shown in FIG. 2B, the gap 103 is almost eliminated, and the outer surface of the deformed tube 20 is brought into close contact with the insertion hole 101, whereby a frictional force acts and the lock bolt 10 Fixing to the insertion hole 101 is completed. A bearing plate 15 is inserted in the vicinity of the water injection side sleeve 30 to substantially support the tunnel outer wall 100.

  At the time of measurement, the probe 2 is brought into contact with the starting end surface 51 of the measuring rod 50 via a contact medium, and ultrasonic waves are incident thereon, and reflected waves from each of the gauge points N1 to N5 and the end surface 52 are received. By multiplying the difference between the transmission time and the reception time of the ultrasonic wave and the sound speed, the round trip distances L1 to L5 of the reflected waves from the gauge points N1-5 and the end face 52 shown in FIG. Further, by obtaining the difference between the L1 to L5, the distance between the gauge points SC1 to SC5 can be calculated, and by comparing with the distances L1 to L5 and SC1 to 5 obtained in advance, the lock bolt 10 It is possible to determine the degree of expansion.

As a specific procedure, the propagation time T _i (i) is determined from the difference between the transmission time of the ultrasonic wave and the reception time of the reflected wave reflected from each of the gauge points N1-5 and the end face 52 shown in FIG. Is the section number). 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 the 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 experiments, it was found that the reflection detection was good at 1 MHz and 2 MHz (low frequency region) in the case of the transverse wave, but the reflected wave detection was good at 5 MHz (high frequency region) in the case of the longitudinal wave. In addition, since the ultrasonic sound speed fluctuates depending on the temperature of the material, in the above processing, temperature correction in accordance with the surrounding environment may be required.

  Next, still another embodiment of the present invention will be described. In addition, the same code | symbol shall be attached | subjected to the member similar to the above-mentioned embodiment.

  In the embodiment of FIG. 7, two measuring rods 50 are provided 50a and 50b, and notch groups G1 and G2 are formed respectively. The first missing group G1 of the first rod 50a is formed in front of the second notched group G2 of the second rod 50b. There are three notches N1 to N3 in the first missing group G1, and the axial forces based on the measurement results are displayed as Pa to Pc in FIG. Further, the notches N3 'to N5 of the second notch group G2 are also three places, and the axial forces based on the measurement results are displayed as Pd to Pf in FIG. The center marks N3 and N3 'are formed at the same position. In addition, the formation position of a notch group and the number of rods can be changed as appropriate.

  In the embodiment shown in FIG. 8, the lock bolt 10 welds or welds the water injection side sleeve 30 and the sealing side sleeve 40 to both ends of the deformed pipe 20 that is a tubular body (hereinafter referred to as “welding”). Furthermore, it has a pair of measuring rods 50 and 50 which are fixed or arranged symmetrically along the deformed tube 20.

  As shown in FIG. 8A, the measuring rod 50 is disposed along the pipe body, or is welded or bonded to a member of a lock bolt such as the deformed pipe 20 or the sleeve 40 or the bearing plate 15 at an appropriate place. It is fixed by. When the measuring rod 50 is fixed, at least both ends of the measuring rod 50 may be fixed to a deformed tube of the lock bolt or a member of the lock bolt. By fixing both ends of the measuring rod 50, the handling of the lock bolt 10 during construction becomes easy. When the measuring rod 50 is disposed along the tube, the tube 20 and the measuring rod 50 are practically integrated by the pressing force of the tube 20 against the drilling hole 101.

  8A and 8B, the start end and the end of the measuring rod 50 are arranged outside the water injection side sleeve 30 and the sealing side sleeve 40, respectively. The measuring rod 50 penetrates the bearing plate 15 through a small hole 17 in the vicinity of the large hole 16 that is continuous with the large hole 16 that penetrates the water injection side sleeve 30, and the start end surface 51 slightly protrudes from the outer surface thereof. By this slight protrusion, the probe 2 can be contacted while preventing interference between the water injection joint (not shown) connected to the water injection side sleeve 30 and the measuring rod 50. A spacer 53 is disposed between the water injection side sleeve 30 and the measuring rod 50. In addition, the ultrasonic wave from the measuring rod 50 to the deformed pipe 20 can be obtained by setting the welded portion 58 to the minimum necessary part at two locations, the vicinity of the water injection side sleeve 30 of the deformed pipe 20 and the outer surface of the sealing side sleeve 40. Leakage is suppressed.

  If ultrasonic attenuation does not become a major obstacle, the embodiment shown in FIG. 8C may be adopted in order to further enhance the integration of the steel pipe expansion type lock bolt and the measuring rod 50. In this embodiment, a threaded portion 58f may be provided at the insertion hole side distal end portion of the measuring rod 50, and the measuring rod 50 may be fixed to the bearing plate 15 with a nut 58g. The fastening means 58x for the measuring rod 50 to the bearing plate 15 may employ various machines such as a latch means in addition to the threaded portion 58f and the nut 58g.

  In the first embodiment, the deformed tube 20 has a single measuring rod 50 disposed in the recess 26 that expands and deforms when expanded. However, in order to maintain the symmetry of deformation, it is preferable that a plurality of the measuring rods 50 are arranged substantially evenly with respect to the expanded tubular body 20.

  In this case, for example, when three measuring rods are used, they may be equally allocated at intervals of 120 degrees. Further, as shown in FIGS. 9A and 9B, a pair of measuring rods 50a and 50b may be both disposed outside the recess 26, and one measuring rod 50a is placed in the recess 26 as shown in FIGS. The other side may be disposed outside the recess 26. Furthermore, as shown in FIGS. 9E and 9F, two measuring rods 50a and 50b may be disposed in the pair of recesses 26 and 26, respectively.

  In each of the above embodiments, the start end surface 51 that is the incident portion 11 is configured as a plane perpendicular to the longitudinal direction of the measuring rod 50. However, if it is desired to make the transverse wave enter smoothly, the starting end face 51a may be formed in an inclined shape in the longitudinal direction of the measuring rod 50 as shown in FIG.

  In the embodiment described above, the measuring rod 50 is expressed as a rod that is also clogged with the central portion. However, since this measuring rod 50 is a concept in the sense that it is filled with the contents compared to the deformed tube 20, even if a cavity along the longitudinal direction exists in the central portion as long as ultrasonic waves can be sufficiently transmitted. Good. When there is a cavity along the longitudinal direction in the central portion of the measuring rod 50, a temperature sensor is inserted into the cavity to measure the temperature of each part, and to measure the axial force with higher accuracy in consideration of temperature correction. Can do.

  In the above embodiment, the measuring rod 50 is directly fixed to the deformed tube 20. However, since it has been found that the attenuation increases when the measuring rod 50 rusts, it is desirable to form a rust preventive film 50x around the measuring rod 50 as shown in FIG. The rust preventive film 50x may be formed using a rust preventive paint or the like in addition to a resin heat shrinkable tube or the like.

  In the said embodiment, although expressed as the axial-force measuring method of a lock bolt, this invention can also be expressed also as the expansion | extension measuring method of a lock bolt.

  The present invention can be used as a rock bolt used in a so-called NATM construction method which is a kind of tunnel construction method.

It is sectional drawing of a rock bolt, and a block diagram of an axial force measuring device. It is sectional drawing etc. in FIG. 1 etc. of a rock bolt, (a) is BB sectional drawing, (d) is BB sectional drawing after expansion | swelling. (A) is a side view showing the relationship between the measuring rod and the notch, (b) is a side view showing the notch position in the entire length of the measuring rod, and (c) is the axis of the measuring rod showing the relationship between the measuring rod and the notch. It is sectional drawing orthogonal to. It is a graph which shows the relationship between the distance to a notch, and an ultrasonic reception amplitude. It is a graph which shows the waveform at each target position in relation to the distance to the notch and the ultrasonic reception amplitude, (a) is a sensitivity adjustment that optimally matches W1, and (b) is an optimal adjustment of W2. Sensitivity adjustment, (c) is a sensitivity adjustment that optimally matches W3, and (d) is a measurement result when the depth of the notch is changed. It is the elements on larger scale of a notch. When two measuring rods are used, (a) is a schematic side view of the lock bolt, (b) is a graph showing the relationship between the distance to the notch in the first measuring rod and the measured axial force. c) is a graph showing the relationship between the distance to the notch in the second measuring rod and the measured axial force. A sectional view of a lock bolt and a block diagram of an axial force measuring device in still another embodiment of the lock bolt, (b) is a front view of the lock bolt as viewed in the direction A, and (c) is an insertion of a measuring rod in still another embodiment. It is an enlarged view of a hole vicinity. It is sectional drawing etc. in another embodiment of a rock bolt, (a) is a BB cross-section equivalent figure of FIG. 2, (d) is the figure after expansion of (a), (c) is other embodiment. FIG. 2 shows a cross-sectional view corresponding to the line BB in FIG. 2, (d) is a view after the expansion of (c), (e) is a cross-sectional view corresponding to the cross-section BB in FIG. FIG. It is a side view which shows another embodiment of the starting end surface of a measuring rod. It is a fragmentary sectional view which shows another aspect of a measuring rod.

Explanation of symbols

1: axial force measuring device, 2: probe, 3: pulser / receiver, 4: PC, 5: monitor, 10: lock bolt, 11: incident part, 12: end, 15: bearing plate, 16: large Hole: 17: Small hole, 20: Deformed tube, 21: Bent outer surface, 22: Bent inner surface, 23: Inside of tube, 30: Injection sleeve, 31: Sleeve tip, 32: Sleeve side, 33: Recess, 34: Water injection hole, 40: sealing side sleeve, 50: measuring rod, 51: start end surface, 52: end surface, 53: spacer, 55: notch, 56: vertical wall portion, 57: flat portion, 58, 58a-c, 58h: welded portion, 58g, 58k: nut, 58f, 58j: threaded portion, 58x: tightening and fixing means, 59: ring spacer, 59x: rod rust coating, 100: tunnel wall, 101: insertion hole, 103: gap , N1-5: Mark (notch) , SC1-6: Distance between gauge points, Sa: Part of ultrasonic wave, Sb: Reflected wave

Claims (7)

Steel pipe expansion type ultrasonic axial force measurement lock bolt,
An inflatable steel pipe and two or more measuring rods for measuring axial force having a point for ultrasonic reflection, each forming a notch group on the measuring rod, and a certain measuring rod and another measuring rod A lock bolt in which the position of the cutout group in the longitudinal direction of the measuring rod is different. The lock bolt according to claim 1, wherein a degree of notch in the measuring rod is increased toward a terminal end side of the measuring rod.   The lock bolt according to claim 2, wherein the degree of the notch is a notch area ratio that is a ratio of an area of the vertical wall portion of the notch to a total cross-sectional area in a cross section orthogonal to the longitudinal direction of the measuring rod.   The lock bolt according to any one of claims 1 to 3, wherein the measuring rod is covered with at least an antirust coating. The degree of notch in the measuring rod is set closer to the end of the measuring rod so that the amplitude y of the reflected signal according to the following equation (1) determined by the distance x from the incident portion of the measuring rod to each notch is measurable. The lock bolt according to claim 1, wherein the lock bolt is increased.
y = exp (cx + d) (1)
However, c and d are constants. A lock bolt axial force measuring method for measuring an axial force acting on the lock bolt according to any one of claims 1 to 4,
Two or more measuring rods for axial force measurement having an expandable steel pipe and a target for ultrasonic reflection, each of the measuring rods is formed with a notch group, Lock bolt axial force measuring method for increasing the degree of notch in the measuring rod toward the end of the measuring rod so that the amplitude y of the reflected signal according to the following equation (1) determined by the distance x to the notch becomes a measurable value .
y = exp (cx + d) (1)
However, c and d are constants. A lock bolt axial force measuring method for measuring an axial force acting on the lock bolt according to any one of claims 1 to 5,
Two or more measuring rods for axial force measurement having an expandable steel pipe and a target for ultrasonic reflection, each of the measuring rods is formed with a notch group, and when the lock bolt is installed in advance, Transmit ultrasonic waves from the incident part, which is the exposed part of the measuring rod, receive the reflected wave from the gauge point, and perform ultrasonic measurement to obtain the reception time difference of the reflected wave from the gauge point. A method for measuring the axial force of the rock bolt, in which the axial force is calculated based on a change in the reception time difference.

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