JPH10318994A - Detection signal processing method for predicting breaking of base rock - Google Patents

Abstract

PROBLEM TO BE SOLVED: To simplify the circuitry for detecting an event by determining the occurrence of event in a detected AE(acoustic emission) wave for each even utilizing the ring down count operation of a counter as it is. SOLUTION: An AE wave detected through an AE sensor 1 is inputted to a comparator 3 and the output therefrom, i.e., a count pulse (e), is daunted by a counter 5 for every unit count time set by a computer 7 to obtain a ring down count. When a peak value exceeding the threshold value of the comparator 3 begins to appear in the detected AE wave, the ring down count is counted at every unit count time and occurrence of event can be determined from the arrangement of the ring clown counts. Since the occurrence of event can be detected only through a combination of the comparator 3 and the counter 5 according to a software in the computer 7, a compact event measuring unit can be realized at a low cost.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for processing a detected acoustic emission wave in predicting rockfall using acoustic emission.

[0002]

2. Description of the Related Art In order to prevent the occurrence of accidents, especially human accidents, caused by the collapse of rocks facing roads, buildings, etc., in general, patrols are regularly conducted at places considered to be dangerous, and visual inspections are conducted. Although rock failure is predicted according to empirical judgment, accurate judgment cannot be obtained because the judgment criteria are extremely unclear, and therefore, serious human accidents should be prevented. It is not possible at present.

As a countermeasure against the above-mentioned dissatisfaction, a technique of using an acoustic emission (hereinafter, referred to as AE) phenomenon for predicting a rock collapse has attracted attention.

[0004] That is, the collapse of the rock mass is caused by the collapse at the crack portion of the entire rock mass including the inside of the rock mass.
An AE sound is always generated for physical changes inside the rock such as a new crack, so this AE sound is detected by the AE sensor, and the degree of the possibility of rock collapse occurring according to the detected AE sound. Judge.

[0005] In the rock fall prediction technology using this AE, various AE parameters are obtained by AE measurement. From many experiments and studies, among various AE parameters, "event" is the most effective one corresponding to the fracture phenomenon. Is considered to be an important parameter.

[0006] The "event" means that the crest value of each detected AE wave is detected, and after the crest value of the crest value exceeding a predetermined threshold value starts to appear, the crest value of the crest value is equal to or less than the threshold value. Is counted as "1 event", and the risk of rock collapse is determined based on the number of events in a certain period.

As shown in FIG. 6, an event is detected by converting an AE wave a (see FIG. 4 (a)) detected by an AE sensor 1 fixed to a bedrock into a shaping circuit composed of an amplifier and a filter circuit. 2, the comparator 3 sets the threshold value b with the adjustment resistor 4, and counts each wave of the AE wave a (see FIG. 4B) whose peak value exceeds the threshold value b by the count pulse e ( The count pulse e is accumulated and counted by a counter 5 which is a frequency counter generally used in an analog circuit.

Since one event is composed of a set of a plurality of count pulses e, some means is required to count the plurality of count pulses e as an event. The device is a pause time method shown in FIG.

The pause time method as an event counting method uses the pause time of one event as 10 based on many data.
msec, and as shown in FIG. 5, from the time t when the peak value of the AE wave first exceeds the threshold value b, the pause signal f is changed to the pause time having the same time length as 10 msec defined as the duration of one event. During the period g, the counting operation of the counter 5 is suspended by the rising pause signal f, whereby the count number of the counter 5 and the event number are made to coincide.

[0010]

However, in the above-mentioned prior art, since the operation of the counter 5 must be paused for a fixed pause time g, the count pulse e is input to the counter 5. After that, means for stopping the counter 5, means for outputting a pause signal f for a fixed pause time g, and the like are required in the circuit configuration. Therefore, the electric circuit configuration for AE wave a signal processing is complicated and large. In addition, there is a problem that it becomes expensive and cannot be easily installed in a dangerous place.

[0011] That is, A which implements the conventional pause time method
As a processing circuit of the E wave a, for example, as shown in FIG.
It is necessary to configure the counter circuit 8 by combining the counter 5 with the AND circuit 9, the flip-flop circuit 10, and the idle time timer 11.

[0012] The counter circuit 8 shown in FIG.
Is input as a signal "1" to one of the input terminals, the signal "1" is input from the flip-flop circuit 10 to the other input terminal.
The AND circuit 9 outputs a signal "1". The signal "1" is input to the counter 5 for counting and the flip-flop circuit 10 is input via the first inverting circuit 12. As a result, the signal "1" is applied to one output terminal (Q terminal) of the flip-flop circuit 10.
And a signal “0” is output to the other output terminal.

A signal "1" from one output terminal of the flip-flop circuit 10 activates a pause time timer 11, and outputs a pause signal f of a pause time g from the pause time timer 11 via a second inversion circuit 13. Input to the C terminal of the flip-flop circuit 10 to keep the state of the flip-flop circuit 10 unchanged while the pause signal f is being input. Is input to the AND circuit 9 and the AND circuit 9
Is held at the signal "0", the counter 5 counts down and pauses while the output of the AND circuit 9 is held at the signal "0", that is, during the pause time g.

As described above, since the pause time g is set to a constant value, and this time is set as the time of one event, the time width of one event of the AE wave a actually detected does not always coincide with that of this event. For this reason, two events that occur consecutively are counted as "1" events, and one event with a long time width is often counted as "2" events, which dissatisfies the accuracy of the obtained event count. There was a problem.

That is, the actual one event time of the AE wave a is substantially in the range of 4 msec to 20 msec. However, even if two AE waves a whose one event time is 4 msec are detected continuously, In this case, it is counted as one event. Conversely, one event time A is 20 msec.
When the E wave a is detected, it is counted as two events.

Since the number of obtained events merely indicates how many AE waves exceeding a threshold value have occurred within a certain period, the intensity (amplitude) of the AE waves is calculated from the obtained events. There was a problem that it was not possible to judge the progress of the rock crushing phenomenon more accurately by the event alone.

Therefore, the present invention has been made in order to solve the above-mentioned problems in the prior art, and uses the ring-down counting operation of the counter as it is to determine the occurrence of detected AE wave events for each event. It is an object of the present invention to make it possible to make a decision, thereby achieving simplification of a circuit configuration for event detection, and obtaining an accurate count of the number of events.

[0018]

According to the present invention, which solves the above technical problem, the invention according to claim 1 is characterized in that the detected AE wave is longer than one cycle of the lowest frequency wave. Counting the ring-down count, which is the number of AE waves exceeding a preset threshold, for each count unit time set shorter than the shortest one event time of the AE waves statistically obtained; That is, the connection of the count unit times in which the counted ring-down count continuously becomes “1” or more is determined as an “1” event.

According to a second aspect of the present invention, in the first aspect of the invention, the detected AE wave is input in parallel to a plurality of comparators each having a different threshold value, and the output of each of the comparators is output. Fill in the counter individually and get a single AE
Detecting a plurality of events having different thresholds from a wave.

According to the third aspect of the present invention, there are provided the first and second aspects.
The count unit time of the described invention was set to 1 msec,
Things.

The detection of the AE sound by the AE sensor is performed by the AE
Of the signal waves sensed by the sensor, it cannot be fixedly determined by the frequency range that is empirically determined to be highly reliable as information or the nature of the rock on which the AE sensor is installed. AE sound sensing ability, AE
For example, a wave in a frequency range of 3 KHz to 50 KHz is detected as an AE wave due to a rock mass transfer characteristic of sound and a regional characteristic of noise.

As described above, since the frequency of the detected AE wave is set, for example, in the range of 3 KHz to 50 KHz, the counting unit time is longer than one cycle of the lowest frequency AE wave. By setting it shorter than one shortest event time of the wave, ie, 4 msec,
When a wave having a peak value exceeding the threshold value is continuously generated in the AE wave, the number of waves is counted for each count unit time.
It is counted as a ring-down count of “1” or more, and the count unit time in which the ring-down count becomes “1” or more continues until a wave having a peak value exceeding the threshold does not occur in the AE wave.

Therefore, if the arrangement of the ring-down count is viewed, a sequence of "1" or more is located in a sequence of "0", and the sequence of "1" or more is regarded as one event. And the time length of this one event is obtained by the product of the continuous number of "1" or more and the count unit time.

The counting operation of the counter is performed at every preset count unit time, the ring-down count of the counter is read at every count unit time, and one event is counted from the read ring-down count. The determination of presence / absence and the calculation of the time width of one detected event are all performed by the computer, so the counter circuit can be configured as a single counter by devising the software of the computer. As a result, the configuration of the counter function part is extremely simplified, and the cost of the apparatus is greatly reduced.

According to the second aspect of the present invention, a single AE
Since a plurality of events having different thresholds can be obtained from the wave, the degree of the strength (amplitude) of the detected AE wave can be determined by comparing the events having different thresholds.

In this case, the counter function part can be constituted by one counter. Therefore, even if a plurality of comparators and counters are provided, the combination structure of the comparators and counters is not complicated, and the individual comparators and counters are not required. Since the power consumption of the counter is small,
There is no danger of a large increase in power consumption, and since the comparator and the counter are inexpensive, the device cost does not increase significantly.

[0027]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. FIG. 1 shows the most basic circuit configuration in which the method of the present invention is carried out. An AE wave a detected by an AE sensor 1 is passed through a shaping circuit 2 and a voltage value of a reference terminal is adjusted by a threshold value by an adjusting resistor 4. is input to the comparison input terminal of the comparator 3 set to b, and the count pulse e, which is the output of the comparator 3, is counted by the counter 5 connected to the clock 6 at every fixed count unit time c set by the computer 7. And ring down count d
And the ring-down count d is calculated by each count unit time c.
The computer 7 reads each time the processing is completed, and stores the read ring-down count d in the computer 7 in order.

The specific processing of the AE wave a by the circuit shown in FIG. 1 is, for example, as shown in FIG.
E wave a is set in advance in the frequency range of 3 KHz to 50 KHz, and the time of one event is statistically 4 msec to 20 ms.
Since it is within the range of ec, a continuous ring-down count d can be obtained even with an AE wave a having a low frequency, and a count unit time c so that even a short event can be detected as an event. Is set to 1 msec.

As apparent from FIG. 2, the detected AE
When a wave having a peak value exceeding the threshold value b of the comparator 3 starts to appear in the wave a, the ring-down count d is counted for each count unit time c. , Ie, “1, 3, 3,
It can be determined from the arrangement of “3, 2” that an “1” event has occurred. The “1” event that has occurred is counted when the count unit time c and the ring-down count d become “1” or more. It can be determined that it is 5 msec which is a product of the number of unit times c.

The ring-down count d counted by the counter 5 is calculated by the computer 7 at the end of each count unit time c.
When the computer 7 is installed in a remote place near a rock where there is a risk of collapse, the computer 7 monitors the danger state of the rock in a wide area by an appropriate method. It is transmitted as data to the main computer of the monitoring station.

FIG. 3 shows a plurality (three in the illustrated embodiment) of the AE sensor 1 set to different thresholds b.
A combination of the comparator 3 and the counter 5 is connected to form a processing circuit for one AE wave a, and a plurality of such processing circuits are connected to one computer 7 to collapse a rock area of a certain size. The degree of danger is monitored.

In the embodiment shown in FIG. 3, the threshold value b set by the adjustment resistor 4 of each comparator 3 in one processing circuit is set to a larger value in order.
Therefore, when an event is detected from the processing circuit set to the high threshold value b, it is possible to determine that the detected AE wave a is strong. It can be accurate and accurate.

[0033]

Since the present invention has the above-described structure, the following effects can be obtained. By devising computer software, the occurrence of an event can be detected only by a combination of a comparator and a counter, so that the hardware structure of the event measuring instrument can be greatly simplified, and the event measuring instrument can be made compact. And at low cost.

Since the event measuring instrument can be manufactured compactly and at low cost, it is possible to install a large number of event measuring instruments in a wide area within a fixed budget, and it is judged that there is a risk of collapse. Monitoring of rock mass can be achieved over a wide area in a detailed manner, and a high accident prevention countermeasure effect can be obtained.

In addition to detecting the occurrence of an event, the time width of each event that has occurred can be known, so that the size and intensity of the detected event can be determined substantially accurately, and the event is used as a parameter. It is possible to accurately determine the degree of risk of rock collapse.

According to the second aspect of the present invention, a single A
Since events having different threshold values can be detected from the E wave, the degree of AE energy of the AE wave that caused the event can be determined substantially accurately, and thus the risk of rock collapse using the event as a parameter. The degree can be accurately determined with extremely high accuracy.

According to the third aspect of the present invention, when an event occurs under an AE wave frequency condition and an event duration condition which are generally determined empirically as appropriate.
Since the ring-down count of "1" or more can be reliably detected within the count unit time, and the count unit time is the least common divisor of the minimum value and the maximum value of the event duration, the calculation process is decided. It will be easier.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing the most basic configuration of an electric circuit configured to carry out the present invention.

FIG. 2 is an explanatory diagram illustrating an example of a detection operation according to the present invention.

FIG. 3 is an electric circuit diagram showing a preferred embodiment of an event detection circuit embodying the present invention.

FIG. 4 is an explanatory diagram of an operation principle of detecting an event from a sensed AE wave.

FIG. 5 is an explanatory diagram showing an operation of a conventional event detection.

FIG. 6 is an electric circuit diagram showing an example of a conventional event detection circuit.

[Explanation of symbols]

 1; AE sensor 2; shaping circuit 3; comparator 4; adjusting resistor 5; counter 6; clock 7; computer 8; counter circuit 9; AND circuit 10; flip-flop circuit 11; pause time timer 12; Second inverting circuit a; AE wave b; threshold value c; count unit time d; ring-down count e; count pulse f; pause signal g; pause time t;

Continuing from the front page (72) Inventor Muneaki Hatanaka 1-5-1, Otsuka, Inzai City, Chiba Pref. Co., Ltd. Inside the Research Institute of Takenaka Corporation (72) Inventor Takao Ueda 8-21-1, Ginza, Chuo-ku, Tokyo Stock Company Company Takenaka Corporation Tokyo head office (72) Inventor Masaaki Endo 1-490 Taiseicho, Omiya-shi, Saitama

Claims (3)

[Claims] 1. The shortest "1" event time of the acoustic emission wave (a), which is longer than one cycle of the lowest frequency wave of the detected acoustic emission wave (a) and is statistically determined. The acoustic emission wave exceeding a preset threshold (b) for each count unit time (c) set shorter than
A ring-down count (d), which is the number of waves in (a), is counted, and the connection of the count unit time (c) in which the counted ring-down count (d) continuously becomes "1" or more is represented by " 1 ”A detection signal processing method for predicting rockfall that is determined to be an event. 2. The detected acoustic emission wave (a) is input in parallel to a plurality of comparators (3) having different thresholds (b), and each of the comparators has a corresponding threshold.
The outputs of (3) are individually input to the counter (5), and the threshold value is obtained from the single acoustic emission wave (a).
2. The method according to claim 1, wherein a plurality of events different from (b) are detected. 3. The detection signal processing method according to claim 1, wherein the count unit time (c) is set to “1 msec”.