JP2001164568A - Stress diagnostic method and stress diagnostic device for ground anchor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To promote accuracy and reliability of a stress diagnosis in a stress diagnostic method and a stress diagnostic device for a ground anchor. SOLUTION: In a ground anchor screwing a nut 8 pushing a structure through an anchor plate 7 in the upper end of a tendon 5 anchoring the lower end side to the ground 3, after stress acting on the anchor plate 7 is measured, tensile stress acting on the tendon 5 is diagnosed based on the measured stress.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention belongs to the technical field of a method and a device for diagnosing stress of a ground anchor for fixing a structure or the like for preventing collapse from falling to the ground.

[0002]

2. Description of the Related Art Generally, a ground anchor of this type is formed by drilling an anchor hole in the ground, inserting a tendon (tensile material) into the anchor hole, and injecting a fixing material such as mortar into the anchor hole to form a tendon. Fixing the lower end side in the ground, temporarily attaching an anchor plate and a nut to the upper end (excess length) of the tendon, applying tension to the tendon using a hydraulic jack, tightening the nut, etc. And the tension of the tendon,
The structure is fixed to the ground by acting on the structure via a nut and an anchor plate.

In the ground anchor constructed as described above, since the tendon may lose its tension due to poor fixing of the tendon to the ground or breakage of the tendon, the tensile stress acting on the tendon is periodically reduced. It has been proposed to diagnose.

[0004]

Therefore, as a method of diagnosing the stress of tendon, a method using a strain gauge, a load cell, an ultrasonic sensor, or the like has already been proposed. However, stress diagnosis using a strain gauge or a load cell has been proposed. It is practically impossible to carry out with existing ground anchors,
In addition, the strain gauges and load cells have a low reliability because they cause measurement errors due to temperature changes and mounting accuracy.

On the other hand, stress diagnosis using an ultrasonic sensor utilizes a characteristic in which the speed of ultrasonic waves propagating through a substance changes according to the stress acting on the substance, as disclosed in Japanese Patent Application Laid-Open No. Hei 7-113231. Therefore, it is theoretically possible to diagnose the tendon stress even with the existing ground anchor, but in the above-mentioned publication, ultrasonic waves are emitted from the upper end of the tendon and the propagation time of the reflected wave is detected. Measuring the tendon stress by measuring the tendon, including measurement errors based on indefinite factors such as tendon dimensions, material, structure, temperature, etc.In particular, measurement errors due to variations in length dimensions are propagated due to stress changes. Since the difference may be larger than the time difference, there is an inconvenience that reliability and practicality are inferior.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in order to solve these problems in view of the above situation, and has a lower end provided on an upper end of a tendon fixed to the ground. In a ground anchor screwed with a nut that presses a structure via an anchor plate, after measuring the stress acting on the anchor plate, diagnosing the tensile stress acting on the tendon based on the measured stress. This is a method for diagnosing the stress of a ground anchor to perform. In other words, since the tensile stress of tendon is indirectly diagnosed based on the stress measurement results of the anchor plate that can easily determine dimensions, material, structure, temperature, etc. As a result, the accuracy and reliability of the stress diagnosis can be improved. Further, at the upper end of the tendon whose lower end is fixed to the ground, in a ground anchor in which a nut for pressing a structure is screwed via an anchor plate, while arranging ultrasonic sensors at a plurality of positions on the anchor plate, It is characterized in that the propagation time of the ultrasonic wave emitted by each ultrasonic sensor is measured, and thereafter, the stress acting on the anchor plate is diagnosed based on the difference between the measurement times. In other words, since the stress of the anchor plate, which changes according to the tensile stress of the tendon, is diagnosed, it is possible to indirectly diagnose the tensile stress of the tendon. Is measured, and stress diagnosis is performed based on the time difference, so that measurement errors due to variations in temperature and plate thickness can be eliminated as much as possible. Further, in the stress diagnosis method, the ultrasonic sensor is disposed at a position near the nut and a position near the outer end of the anchor plate. In other words, in the stress distribution of the anchor plate, two places having a large difference are specified and the propagation time of the ultrasonic wave is measured, so that the difference between each measurement time can be made as large as possible. The ratio of the included errors can be made as small as possible. Further, in the stress diagnosis method, the propagation time of the ultrasonic wave is measured by using a sing-around method. That is, since transmission and reception of ultrasonic waves are repeated a predetermined number of times and the propagation time is integrated, highly accurate stress diagnosis can be performed even on an anchor plate having a smaller size than tendons. Further, in the stress diagnosis method,
Each ultrasonic sensor is configured by combining a transmitter that emits a surface SH wave and a receiver that receives the surface SH wave emitted by the transmitter at a position at a predetermined interval. Is what you do. In other words, since the propagation time of the ultrasonic wave is measured on the front surface of the anchor plate, a measurement result independent of the plate thickness can be obtained. As a result, even if the parallelism of the front and back surfaces of the anchor plate is not maintained, the accuracy can be improved. High stress diagnosis can be performed. Further, a stress diagnostic device for a ground anchor in which a nut for pressing a structure via an anchor plate is screwed to an upper end portion of a tendon having a lower end fixed to the ground, wherein the stress diagnostic device is provided on the anchor plate. Ultrasonic sensors arranged at a plurality of locations, propagation time measuring means for measuring the propagation time of ultrasonic waves emitted by each ultrasonic sensor, and diagnosing stress acting on the anchor plate based on a difference between the measurement times A stress diagnosis device for a ground anchor, comprising: a stress diagnosis unit. In other words, since the stress of the anchor plate, which changes according to the tensile stress of the tendon, is diagnosed, it is possible to indirectly diagnose the tensile stress of the tendon. Is measured, and stress diagnosis is performed based on the time difference, so that measurement errors due to variations in temperature and plate thickness can be eliminated as much as possible. Further, in the stress diagnostic apparatus, the ultrasonic sensor is disposed at a position near the nut and a position near the outer end of the anchor plate. In other words, in the stress distribution of the anchor plate, two places having a large difference are specified and the propagation time of the ultrasonic wave is measured, so that the difference between each measurement time can be made as large as possible. The ratio of the included errors can be made as small as possible. Further, in the stress diagnosis apparatus, the propagation time measuring means measures the propagation time of the ultrasonic wave by using a sing-around method. That is, since transmission and reception of ultrasonic waves are repeated a predetermined number of times and the propagation time is integrated, highly accurate stress diagnosis can be performed even on an anchor plate having a smaller size than tendons. Further, in the stress diagnosis device, each ultrasonic sensor combines a transmitter that emits a surface SH wave and a receiver that receives the surface SH wave emitted by the transmitter at a position at a predetermined interval. It is characterized by comprising. In other words, since the propagation time of the ultrasonic wave is measured on the front surface of the anchor plate, a measurement result independent of the plate thickness can be obtained. As a result, even if the parallelism of the front and back surfaces of the anchor plate is not maintained, the accuracy can be improved. High stress diagnosis can be performed.

[0007]

Next, one embodiment of the present invention will be described with reference to the drawings. In the drawings, reference numeral 1 denotes a ground anchor constructed to fix the ground-fall prevention structure 2 to the ground 3.
A step of drilling an anchor hole 4 in the ground 3, a step of inserting a tendon (tensile material) 5 into the anchor hole 4, and injecting a fixing material 6 such as mortar into the anchor hole 4 so that the lower end of the tendon 5 is grounded. A step of temporarily attaching the anchor plate 7 and the nut 8 to the upper end (excess length) of the tendon 5, a step of applying tension to the tendon 5 using a hydraulic jack (not shown), It is constructed through a process of tightening the nut 8 and the like. Then, the tension of the tendon 5 acts as a pressing force on the structure 2 via the nut 8 and the anchor plate 7, and the structure 2 is fixed to the ground 3 by the pressing force. As before.

The tendon 5 includes a PC tension member 9 formed of a cable material or a shaft material, a fixing body (ground fixing portion) 10 integrally connected to a lower end side of the PC tension member 9, a PC
Although it is configured using a plurality of members such as a condominium (nut screw portion) 11 integrally connected to the upper end side of the tension member 9, most of the members are inserted into the anchor holes 4, so that the existing members are used. In the ground anchor 1, it is practically impossible to specify the size, material, structure, temperature, and the like of the tendon 5.

On the other hand, the anchor plate 7 has various dimensions, and an appropriate one is selected according to the conditions of each site (tendon tension, etc.). Since the anchor plate 7 is exposed to the outside, the dimensions, material, structure, temperature and the like of the anchor plate 7 can be easily specified even in the existing ground anchor 1.

Reference numeral 12 denotes a stress diagnostic device for the ground anchor 1. The stress diagnostic device 12 emits an ultrasonic wave to the anchor plate 7 and receives the emitted ultrasonic wave. 13, the ultrasonic transceiver 1
3. A sing-around sound velocity measuring unit 14 that measures the propagation time of the ultrasonic wave based on the transmission and reception of the ultrasonic wave in 3, and diagnoses the stress acting on the anchor plate 7 or the tendon 5 based on the measurement result in the sing-around sound velocity measuring unit 14. It comprises a stress diagnosis unit 15 (for example, a portable personal computer). That is, the stress diagnostic apparatus 12 can measure the stress acting on the anchor plate 7 by using the characteristic that the speed of the ultrasonic wave propagating through the substance changes according to the stress acting on the substance. Instead, it is possible to indirectly diagnose the tensile stress acting on the tendon 5 based on the result of measuring the stress acting on the anchor plate 7. Therefore, the tensile stress of the tendon 5 can be indirectly diagnosed based on the stress measurement result of the anchor plate 7 which can easily determine the dimensions, the material, the structure, the temperature, and the like. It is possible to improve the accuracy and reliability of the stress diagnosis as compared with the case where the stress diagnosis is performed directly.

A pair of ultrasonic sensors 16 and 17 are disposed at a predetermined interval in the ultrasonic transmitting and receiving unit 13. Each of the ultrasonic sensors 16 and 17 is provided with an anchor plate 7.
16a, 17a for emitting ultrasonic waves to the receiver and a receiver 16 for receiving ultrasonic waves emitted by the transmitters 16a, 17a
b, 17b. That is, the anchor plate 7
Since the propagation time of ultrasonic waves can be measured at the above two points, stress diagnosis based on the difference between the measurement times can be performed, and as a result, errors due to temperature and thickness variations can be minimized. It is possible to improve the accuracy of stress diagnosis by eliminating the stress.

The ultrasonic sensors 16, 17
Are selected and arranged at two locations where there is a large difference in the stress distribution of the anchor plate 7. That is, in order to measure the propagation time of the ultrasonic wave by arranging the ultrasonic sensors 16 and 17 at a position near the nut directly receiving the tension of the tendon 5 and a position near the outer end separated from the position near the nut, respectively. The difference in measurement time can be made as large as possible,
As a result, it is possible to reduce the ratio of errors included in the measurement result as much as possible.

In this embodiment, the ultrasonic sensors 16 and 17 are attached to the surface of the anchor plate 7 by the surface SH.
Waves (horizontally polarized)
Transmitters 16a, 17 firing a shear wave)
a, and receivers 16b, 17 for receiving surface SH waves emitted by the transmitters 16a, 17a at predetermined intervals.
b and a surface SH wave sensor in combination with each other to measure the propagation time of the ultrasonic wave at the surface of the anchor plate 7, so that a measurement result independent of the plate thickness can be obtained.
As a result, it is possible to perform highly accurate stress diagnosis even on the anchor plate 7 where the front and back surfaces are not kept parallel.

On the other hand, the sing-around sound velocity measuring unit 1
The anchor plate 4 is configured to measure the propagation time of the ultrasonic wave by using the sing-around method of repeating the transmission and reception of the ultrasonic wave a predetermined number of times to accumulate the propagation time. 7, a highly accurate stress diagnosis can be performed. That is, the sing-around sound velocity measuring unit 14 includes a synchronization pulse generator 18 for generating a synchronization pulse of a predetermined period, a pulser 19 for exciting the transmitters 16a and 17a with the pulse generated by the synchronization pulse generator 18, a receiver 16b, An amplifier 20 for amplifying the reception wave of 17b, a zero cross 22 for detecting a propagation time based on a predetermined reception wave and outputting a trigger signal;
A delay unit 23 for delaying the trigger signal output from the zero cross 22 by a predetermined time and generating a pulse again in the synchronous pulse generator 18, a counter 24 for counting the number of trigger outputs of the delay unit 23, and setting a trigger level in the zero cross 22. , A sensor switching unit 26 for switching the ultrasonic sensors 16 and 17 to be measured, and the like, for example, repeating the above time detection operation 10,000 times to perform highly accurate propagation time measurement. It becomes possible.

The storage unit of the stress diagnosis unit 15 includes:
A program such as "Sing-around setting" for setting the measurement conditions of the sing-around sound velocity measuring unit 14, "Stress diagnosis" for diagnosing the stress acting on the anchor plate 7 or the tendon 5 based on the measurement result of the sing-around sound velocity measuring unit 14. Is stored in advance, and a control procedure of “stress diagnosis” which is a main part of the present invention will be described below with reference to a flowchart.

In the "stress diagnosis", first, a dimension data input screen of the anchor plate 7 is displayed, and then input determination of the dimension data is performed. If the determination is YES, a measurement start standby screen is displayed. Here, when the measurement start operation is determined, the measurement command using one ultrasonic sensor 16 is output to the sing-around sound velocity measuring unit 14 and the measured value is stored, and then the other ultrasonic sensor 17 is The used measurement command is output to the sing-around sound velocity measuring unit 14 and the measured value is stored. And after storing both measurements,
The difference between the two measured values is calculated, and stress data (anchor plate stress and tendon stress) corresponding to the calculated value is extracted with reference to a stress data table prepared for each dimension of the anchor plate 7. Is displayed and one stress diagnosis is completed.

In the ground anchor 1 constructed as described above, a nut 8 for pressing the structure 2 via an anchor plate 7 is screwed to the upper end of the tendon 5 whose lower end is fixed to the ground 3. After the stress acting on the anchor plate 7 is measured, the tensile stress acting on the tendon 5 is diagnosed on the basis of the measured stress. Accuracy and reliability can be increased.

Further, the ultrasonic sensors 16 and 17 are arranged at a plurality of positions on the anchor plate 7, and the propagation times of the ultrasonic waves emitted by the respective ultrasonic sensors 16 and 17 are measured. Since the stress acting on the anchor plate 7 is diagnosed on the basis of the difference between the two, it is possible to eliminate as much as possible a measurement error caused by a variation in temperature or plate thickness.

Further, since the ultrasonic sensors 16 and 17 are arranged at the position near the nut and the position near the outer end of the anchor plate 7, the ultrasonic wave propagation time at two places where the stress distribution of the anchor plate 7 is large is large. Can be measured, and as a result, the difference between the measurement times can be made as large as possible to reduce the error ratio.

Further, since the propagation time of the ultrasonic wave is measured by using the sing-around method, highly accurate stress diagnosis can be performed even in the anchor plate 7 having a smaller size than the tendon 5.

The ultrasonic sensors 16 and 17 receive the transmitters 16a and 17a for emitting surface SH waves and the surface SH waves emitted by the transmitters 16a and 17a at positions at predetermined intervals. Since it is configured by combining the receivers 16b and 17b, a measurement result independent of the plate thickness can be obtained. As a result, a high-precision stress can be obtained even in the anchor plate 7 where the front and back surfaces are not kept parallel. Diagnosis can be made.

The present invention is, of course, not limited to the above-described embodiment. For example, if the stress of the tendon 5 is indirectly diagnosed based on the stress measurement of the anchor plate, the present invention is not limited to this. It is needless to say that the present invention includes a device that performs stress measurement using a sensor other than the acoustic wave sensor.

In the above embodiment, the surface SH wave sensor is used as the ultrasonic sensor. For example, the oblique SH wave is incident at a predetermined angle from the upper surface of the anchor plate and is reflected on the lower surface of the anchor plate. The transmission / reception principle uses an ultrasonic sensor having a different measuring method, such as an oblique angle SH wave sensor that receives ultrasonic waves, or an electromagnetic ultrasonic transducer (EMAT) that can transmit and receive ultrasonic waves electromagnetically. Different ultrasonic sensors may be used.

[Brief description of the drawings]

FIG. 1 is an overall sectional view of a ground anchor.

FIG. 2 is a block diagram illustrating a configuration of a stress diagnosis device.

FIG. 3A is a plan view showing an arrangement of an ultrasonic sensor.
(B) is an XX cross-sectional view.

FIG. 4 is a flowchart illustrating a control procedure of a stress diagnosis unit.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Ground anchor 2 Structure for preventing ground collapse 3 Ground 4 Anchor hole 5 Tendon 6 Fixing material 7 Anchor plate 8 Nut 12 Stress diagnostic device 13 Ultrasonic transmitting / receiving unit 14 Singaround sound speed measuring unit 15 Stress diagnostic unit 16 Ultrasonic sensor 17 Ultra Sound wave sensor

Continued on the front page (72) Inventor Kazuhiro Yamakawa 1093 Tsumanuma, Ouma-gun, Osato-gun, Saitama Prefecture Inside Azuma Systems Co., Ltd. (72) Inventor Masao Fukudome 2-26-11 Minami Tokiwadai, Itabashi-ku, Tokyo Power Sonic (72) Inventor Motoaki Ishikawa 3-16-20 Tagara, Nerima-ku, Tokyo Just System Co., Ltd. F-term (reference) 2D041 GA01 GC00 GC01

Claims (9)

[Claims] The present invention relates to a ground anchor having a lower end screwed to a nut for pressing a structure via an anchor plate on an upper end of a tendon having a lower end fixed to the ground. A method for diagnosing the stress of a ground anchor, comprising diagnosing a tensile stress acting on a tendon based on a measured stress. 2. An ultrasonic sensor is disposed at a plurality of positions on an anchor plate of a ground anchor in which a nut for pressing a structure via an anchor plate is screwed to an upper end of a tendon having a lower end fixed to the ground. And measuring the propagation time of the ultrasonic waves emitted by each ultrasonic sensor, and then diagnosing the stress acting on the anchor plate based on the difference between the respective measurement times. . 3. The method for diagnosing stress of a ground anchor according to claim 2, wherein the ultrasonic sensors are arranged at a position near the nut and a position near the outer end of the anchor plate. 4. The method for diagnosing stress of a ground anchor according to claim 2, wherein the propagation time of the ultrasonic wave is measured using a sing-around method. 5. The ultrasonic sensor according to claim 2, wherein each of the ultrasonic sensors transmits a surface SH wave, and a receiver receives the surface SH wave emitted by the transmitter at a position at a predetermined interval. And a method for diagnosing stress of a ground anchor. 6. A stress diagnostic device for a ground anchor in which a nut for pressing a structure via an anchor plate is screwed to an upper end portion of a tendon having a lower end fixed to the ground, wherein the stress diagnostic device comprises: Ultrasonic sensors arranged at a plurality of locations on the anchor plate, propagation time measuring means for measuring the propagation time of ultrasonic waves emitted by each ultrasonic sensor, and stress acting on the anchor plate based on the difference between each measurement time And a stress diagnosis means for diagnosing the stress. 7. The stress diagnosis device for a ground anchor according to claim 6, wherein the ultrasonic sensors are arranged at a position near the nut and a position near the outer end of the anchor plate. 8. The stress diagnosis apparatus for a ground anchor according to claim 6, wherein the propagation time measuring means measures the propagation time of the ultrasonic wave by using a sing-around method. 9. The ultrasonic sensor according to claim 6, wherein each of the ultrasonic sensors emits a surface SH wave and a receiver that receives the surface SH wave emitted by the transmitter at a predetermined interval. And a stress diagnosis device for a ground anchor.