JP2001004438A - Ultrasonic vibration detection sensor and ultrasonic vibration measuring method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ultrasonic vibration detection sensor, which is stably fitted to a rock bed and can accurately measure ultrasonic vibration that the rock bed generates, and the ultrasonic vibration measuring method. SOLUTION: This is a sensor used to predict the falling of a rock bed R by measuring as an electric signal the ultrasonic vibration that the rock bed R generates when breaking or deforming and the sensor is constituted by forming a hole 2 in the rock bed R, positioning in the hole 2 a piezoelectric element 4 which is fixed to a lid material 3 closing the opening part of the hole 2 through a fixed rod 5 and made waterproof, and also filling the hole 2 with water 6.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an acoustic emission (AE) generated when rock (including rock) is broken or deformed using a sensor (hydrophone) in which a piezoelectric element is immersed in water. The present invention relates to an ultrasonic vibration detecting sensor and an ultrasonic vibration measuring method used for measuring rock mass and predicting a rock collapse.

[0002]

2. Description of the Related Art In recent years, large-scale rock collapse accidents on steep slopes, especially near tunnel entrances, have occurred frequently. In order to prevent such accidents, a piezoelectric element (PZT element) is conventionally used as a sensor to measure AE (Acoustic Emission = Ultrasonic Vibration) emitted at the time of minute destruction or deformation in rock. An AE sensor 19 is used. As shown in FIG. 10, this conventional AE sensor is mounted directly on the surface of a bedrock R using an adhesive 20, and directly receives AE emitted from the bedrock R.

[0003]

However, the conventional AE sensor 19 has the following problems. That is, since the AE sensor 19 is configured by attaching the piezoelectric element 4 to the surface of the bedrock R with the adhesive 20, the AE sensor 19 is stably fixed to the bedrock R due to the presence of irregularities and cracks on the surface of the bedrock R. It is difficult. For this reason, there has been a problem that the AE cannot be accurately measured due to lack of fixing force to the bedrock R or detachment from the bedrock R.

Accordingly, an object of the present invention is to provide an ultrasonic vibration detection sensor and an ultrasonic vibration detection sensor which are stably mounted on a rock mass R and can always accurately measure ultrasonic vibrations emitted from the rock mass R. It is to provide a measuring method.

[0005]

In order to achieve the above object, an ultrasonic vibration detecting sensor (1) according to the first aspect of the present invention is an ultrasonic vibration detecting sensor (1) which is generated when a rock (R) breaks or deforms. A sensor used to predict the collapse of a rock (R) by measuring sound wave vibrations as an electric signal, forming a perforation (2) in the rock (R) and closing an opening of the perforation (2). The piezoelectric element (4) fixed to the cover (3) to be fixed via the fixing rod (5) and subjected to waterproofing is positioned in the perforation (2), and the water (6) is introduced into the perforation (2). ) Is filled.

According to a second aspect of the present invention, there is provided an ultrasonic vibration detecting sensor according to the first aspect, wherein the wall surface of the perforation is covered with a wall material. And

Further, the ultrasonic vibration detecting sensor (1) according to the third aspect measures the ultrasonic vibration generated when the rock (R) is broken or deformed as an electric signal, and detects the collapse of the rock (R). A sensor used for prediction, in which a perforation (2) is formed in a rock (R), and a cylinder (13) is inserted and assembled into the perforation (2). A water-cooled piezoelectric element (4), which is fixed via a fixing rod (5) to a lid (14) for closing the upper end of the cylindrical part (13) via a fixing rod (5), is positioned in the water (6). ) Is filled.

According to a fourth aspect of the present invention, there is provided an ultrasonic vibration measuring method, wherein a waterproof piezoelectric element (4) is attached to a rock (R) with water (6) interposed therebetween. It is characterized in that the ultrasonic vibration generated at the time of destruction or deformation is received by the piezoelectric element (4) via water and measured as an electric signal.

Symbols in parentheses indicate corresponding elements or matters described in the drawings and the embodiments of the invention described later.

According to the ultrasonic vibration detecting sensor according to the first aspect of the present invention, since the piezoelectric element which has been subjected to waterproof processing is attached to the perforation formed in the rock through water, the sensor is mounted on the rock. Can be securely mounted. Therefore, the ultrasonic vibration emitted from the rock can be accurately measured.

Further, since the ultrasonic vibration detection sensor uses a hydrophone, which is a sensor in which a piezoelectric element is immersed in water, it is possible to measure ultrasonic vibration more accurately. That is, the conventional AE sensor attaches the piezoelectric element directly to the bedrock via an adhesive, so that it is easy to pick up noise, and this has an adverse effect on the measurement of ultrasonic vibration. It is difficult to pick up unnecessary noise because it is immersed. In addition, it is generally known that water has excellent conductivity of ultrasonic vibration waves, and according to the ultrasonic vibration detection sensor according to the present invention using a hydrophone, the ultrasonic vibration is more accurately detected. Can be measured.

The inventor of the present invention conducted an experiment to compare the sensitivity of the ultrasonic vibration detection sensor according to the present invention with the conventional AE sensor. In this experiment, as shown in FIG. 7, the ultrasonic vibration detection sensor 1 according to the present invention and the conventional AE sensor 19 are R-set on the rock, and the rock R is equidistant from both sensors 1 and 19 at the same position. Beaded ball 1
8 was divided and the waveform was measured. The results are shown in the graph of FIG. FIG. 8A shows the ultrasonic vibration detection sensor 1 according to the present invention, and FIG. 8B shows the conventional AE sensor 1.
9. As is clear from this graph,
In the measurement by the ultrasonic vibration detection sensor 1 according to the present invention, since the maximum amplitude of the waveform is larger and the waveform is clearer than that of the conventional AE sensor 19, it can be seen that the sensitivity is excellent. As a result, the ultrasonic vibration detection sensor 1 according to the present invention has a higher rock mass R than the conventional AE sensor 19.
It was proved that it was more excellent as a sensor, including that it could be installed reliably.

According to the second aspect of the present invention, in addition to the effects of the first aspect, the wall surface of the perforation is covered with a wall material, so that even if a crack or the like occurs in the rock, the perforation is performed. You can keep the water inside without leaking. Thus, the waterproofed piezoelectric element can always be immersed in water, and the ultrasonic vibration can be accurately measured.

According to a third aspect of the present invention, in addition to the functions and effects of the first or second aspect, a cylindrical portion is inserted and assembled into a hole formed in the rock, and the inside of the cylindrical portion is formed. Since the piezoelectric element is located at the same time and filled with water, it is possible to more reliably maintain the state in which the waterproofed piezoelectric element is immersed in water. Therefore, more accurate measurement of the ultrasonic vibration becomes possible.

According to the fourth aspect of the present invention, the piezoelectric element is attached to the bedrock with water interposed therebetween, and the ultrasonic vibration generated when the bedrock is broken or deformed is received by the piezoelectric element via the water. Therefore, the ultrasonic vibration emitted from the rock reaches the piezoelectric element through water having excellent conductivity. Therefore, the ultrasonic vibration can be accurately measured.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An ultrasonic vibration detecting sensor 1 and an ultrasonic vibration measuring method according to a first embodiment of the present invention will be described with reference to FIG. 1A is a front sectional view showing a state in which the ultrasonic vibration detection sensor 1 is installed on a rock R, FIG. 1B is a plan view thereof, and FIG. 1C is a sectional perspective view showing a piezoelectric element 4 portion thereof. The same parts as those shown in the conventional example are denoted by the same reference numerals.

This ultrasonic vibration detection sensor 1 is a rock mass R
Is to measure the ultrasonic vibration (= AE) generated at the time of breaking or deformation as an electric signal to predict the collapse of the rock R, and to form a cylindrical hole (bore hole) 2 in the rock R, A piezoelectric element 4 fixed via a fixing rod 5 to a lid member 3 closing an upper end opening of the perforation 2 is located, and water 6 is filled in the perforation 2.

The piezoelectric element 4 is fixed in a stainless steel housing 7 with an epoxy-based adhesive 8 and is waterproofed. The reason why the waterproof processing is performed in this way is to prevent electricity from flowing outside through the water 6 when the piezoelectric element 4 comes into direct contact with the water 6 and to efficiently receive a signal coming from outside. . The housing 7 is connected to the fixing rod 5. A coaxial cable 9 is disposed in the fixed rod 5 via a preamplifier 25, and the distal end thereof is connected to the piezoelectric element 4. The lid member 3 is made of rubber, and its lower part is fitted into the upper end opening of the perforation 2 to close the upper end opening. The shape of the portion of the piezoelectric element 4 may be a disk shape as shown in FIG. 1 or a spherical shape as shown in FIG.

Since the ultrasonic vibration detection sensor 1 according to the present embodiment can be securely mounted on the bedrock R,
Ultrasonic vibration emitted from the bedrock R can be accurately measured. Further, since the ultrasonic vibration detection sensor 1 uses a hydrophone, which is a sensor in which the piezoelectric element 4 is immersed in water 6, it is difficult to receive noise and effectively receive ultrasonic vibration waves. Therefore, the ultrasonic vibration can be accurately measured. In addition, since the upper end opening of the perforation 2 is closed by the lid member 3, the water 6 in the perforation 2 hardly evaporates, and the amount thereof is maintained constant for a long period of time.

Referring to FIG. 3, an ultrasonic vibration detecting sensor 1 and an ultrasonic vibration measuring method according to a second embodiment of the present invention will be described. FIG. 3A is a front sectional view showing the ultrasonic vibration detection sensor 1, and FIG. 3B is a plan view thereof. The ultrasonic vibration detecting sensor 1 is characterized in that a cover 10 made of stainless steel or plastic is fixed on the upper surface of the rubber lid member 3 with bolts 11 and covered. By doing so, the rubber-made lid member 3 that is easily damaged by solar heat or the like is protected, and the function of the lid member 3 can be favorably maintained for a long period of time.

Referring to FIG. 4, an ultrasonic vibration detecting sensor 1 and an ultrasonic vibration measuring method according to a third embodiment of the present invention will be described. FIG. 4 shows an ultrasonic vibration detection sensor 1
FIG. In the ultrasonic vibration detection sensor 1, the wall surface of the perforation 2 formed in the rock R is covered with a wall material 12 formed by applying cement, mud, or the like. Thus, even if cracks or the like occur in the rock R, the water 6 in the perforations 2 can be maintained without leaking, and the ultrasonic vibration can be accurately measured by always immersing the piezoelectric element 4 in the water 6. it can.

Referring to FIG. 5, an ultrasonic vibration detecting sensor 1 according to a fourth embodiment of the present invention will be described. FIG.
(A) is a front sectional view showing the ultrasonic vibration detection sensor 1, and (b) is a plan view thereof. This ultrasonic vibration detection sensor 1 has a lid formed by forming a perforation 2 in a bedrock R, inserting and assembling a tubular portion 13 into the perforated hole 2, and closing the upper end opening of the tubular portion 13 in the tubular portion 13. The piezoelectric element 4 is fixed to the portion 14 via the fixing rod 5 and is filled with water 6. The piezoelectric element 4 is housed in a housing 7. In the present embodiment, the cylindrical portion 13 is made of stainless steel, and the lid portion 14 is configured by fitting an interior material 16 made of rubber into an exterior material 15 made of stainless steel or plastic. Note that it is preferable that the cylinder 13 is fixed to the wall by pouring cement, silicon, or the like between the wall of the perforation 2 and the cylinder 13.

This ultrasonic vibration detection sensor 1 is a rock mass R
The cylindrical portion 13 is inserted and assembled into the perforation 2 formed in the above, and the upper end opening of the cylindrical portion 13 is closed by the lid portion 14. Therefore, the predetermined amount of water 6 is maintained for a long time without reducing. Therefore, it is possible to more accurately measure the ultrasonic vibration.

Referring to FIG. 6, an ultrasonic vibration detecting sensor 1 and an ultrasonic vibration measuring method according to a fifth embodiment of the present invention will be described. FIG. 6 shows an ultrasonic vibration detection sensor 1
FIG. The feature of this ultrasonic vibration detection sensor 1 is that not only the upper end of the housing 7 housing the piezoelectric element 4 is connected to the fixed rod 5 but also the lower end is connected to the support rod 17. Is screwed to the bottom wall of the cylindrical portion 13. By doing so, the piezoelectric element 4 can be positioned in the cylindrical portion 13 in a more stable posture, and more accurate ultrasonic vibration measurement can be performed. The connection between the housing 7 and the fixing rod 5 and the connection between the storage body 7 and the support rod are both achieved by screwing.

FIG. 9 shows an example of a monitoring system for predicting the collapse of the rock R using the ultrasonic vibration detection sensor 1 according to the present invention. In this system, four ultrasonic vibration detection sensors 1 (ch1 to ch)
4) is attached, and an electric signal corresponding to the ultrasonic vibration received by the sensor 1 is transmitted to the personal computer 22 provided at the site.
The personal computer 22 processes the transmitted electric signal, transmits the data to the receiver 23 in the control room by the transmitter 21, and processes the data in the personal computer 22 in the control room. Then, when there is a risk of the rock R falling down, a predetermined danger signal is transmitted to notify that effect. This allows
This is to avoid accidents due to rock R collapse.

[0026]

As described above, according to the ultrasonic vibration detecting sensor according to the first aspect of the present invention, since the piezoelectric element which has been subjected to waterproof processing is attached to the hole formed in the rock through water. It can be reliably mounted on the rock and can accurately measure the ultrasonic vibration emitted from the rock.
This makes it possible to more accurately predict the collapse of the rock mass and prevent the accident of the rock mass collapse.

Further, since the ultrasonic vibration detection sensor uses a hydrophone, which is a sensor in which a piezoelectric element is immersed in water, the ultrasonic vibration is detected by the water having excellent conductivity of ultrasonic vibration waves. It can measure more accurately. Therefore, the rock collapse accident can be prevented beforehand.

According to the second aspect of the present invention, in addition to the function and effect of the first aspect of the present invention, the wall surface of the perforation is covered with the wall material, so that the perforation can be performed even if a crack or the like occurs in the rock. You can keep the water inside without leaking. Thereby, the waterproofed piezoelectric element can be always immersed in water, and the ultrasonic vibration can be measured accurately, which contributes to prevention of rock accident.

According to the third aspect of the present invention, in addition to the functions and effects of the first or second aspect of the present invention, a tubular portion is inserted and assembled into a bore formed in the rock, and Since the piezoelectric element is located at the same time and filled with water, it is possible to more reliably maintain the state in which the waterproofed piezoelectric element is immersed in water. Therefore, it is possible to more accurately measure ultrasonic vibration, which leads to prevention of accidents.

According to the fourth aspect of the present invention, the piezoelectric element is attached to the bedrock with water interposed therebetween, and the ultrasonic vibration generated when the bedrock is broken or deformed is received by the piezoelectric element via the water. Therefore, the ultrasonic vibration emitted from the rock reaches the piezoelectric element through water having excellent conductivity. Therefore, the ultrasonic vibration can be measured accurately,
This also makes it possible to prevent a rock collapse accident from occurring.

[Brief description of the drawings]

FIG. 1 shows an ultrasonic vibration detection sensor according to a first embodiment of the present invention, wherein (a) is a front sectional view thereof,
(B) is a plan view, and (c) is a cross-sectional perspective view showing the piezoelectric element portion.

FIG. 2 is a cross-sectional perspective view showing another piezoelectric element portion of the ultrasonic vibration detection sensor according to the first embodiment of the present invention.

3A and 3B show an ultrasonic vibration detection sensor according to a second embodiment of the present invention, wherein FIG.
(B) is a plan view.

FIG. 4 is a front sectional view showing an ultrasonic vibration detection sensor according to a third embodiment of the present invention.

5A and 5B show an ultrasonic vibration detection sensor according to a fourth embodiment of the present invention, wherein FIG.
(B) is a plan view.

FIG. 6 is a front sectional view showing an ultrasonic vibration detection sensor according to a fifth embodiment of the present invention.

FIG. 7 shows an ultrasonic vibration detection sensor of the present invention and a conventional AE.
It is a perspective view which shows the technique of the sensitivity experiment of a sensor.

FIGS. 8A and 8B are graphs showing the results of the sensitivity experiment shown in FIG. 6, in which FIG. 8A shows the result of the ultrasonic vibration detection sensor of the present invention, and FIG. 8B shows the result of the conventional AE sensor.

FIG. 9 is a configuration diagram showing an example of a monitoring system for predicting a rock collapse using an ultrasonic vibration detection sensor according to the present invention.

FIG. 10 is a front sectional view showing a conventional AE sensor.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Ultrasonic vibration detection sensor 2 Perforation 3 Cover material 4 Piezoelectric element 5 Fixing rod 6 Water 7 Container 8 Epoxy adhesive 9 Coaxial wire 10 Cover 11 Bolt 12 Wall material 13 Tube part 14 Cover part 15 Exterior material 16 Interior material 17 Support rod 18 Bead ball 19 AE sensor 20 Adhesive 21 Transmitter 22 Personal computer 23 Receiver 25 Preamplifier R Bedrock

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Shun Yanagiya, Gokasho, Uji, Kyoto Prefecture F-term in the Earthquake Prediction Research Center, Disaster Prevention Research Institute, Kyoto University GE05 GH05 2G064 AB01 AB02 AB24 AB29 BA02 BD18 BD35 BD61 DD05

Claims (4)

[Claims] 1. A sensor used for predicting a collapse of a rock by measuring an ultrasonic vibration generated when the rock breaks or deforms as an electric signal, wherein a hole is formed in the rock and an opening of the hole is formed. Ultrasonic vibration detection, characterized in that a piezoelectric element, which is fixed via a fixing rod to a cover material for closing the part and is subjected to waterproof processing, is located in the perforation and filled with water. sensor. 2. The ultrasonic vibration detection sensor according to claim 1, wherein a wall surface of the perforation is covered with a wall material. 3. A sensor which is used for predicting a collapse of a rock by measuring ultrasonic vibrations generated when the rock breaks or deforms as an electric signal, wherein a perforation is formed in the rock and the perforation is formed in the rock. A piezoelectric element which is fixed via a fixing rod to a lid for closing the upper end of the cylindrical part via a fixing rod and is subjected to waterproofing is positioned inside the cylindrical part, and water is provided inside the cylindrical part. Ultrasonic vibration detection sensor characterized by being filled. 4. A waterproof piezoelectric element is attached to a bedrock with water interposed therebetween, and an ultrasonic vibration generated when the bedrock is broken or deformed is received by the piezoelectric element via water to generate an electric signal. An ultrasonic vibration measurement method characterized in that measurement is performed as an ultrasonic wave.