JPH03202504A - Detector for ground changing state with ae sensor and detecting method - Google Patents

Abstract

PURPOSE:To secure reliability by bending a wave guide with AE sensors fitted at both ends, to be inserted into an external pipe via bearing bodies, and by transmitting AE sound on one side, to the wave guide, to set it in relation to nontransmission on the other side. CONSTITUTION:The bar-shaped wave guide 3 of a required length with AE sensors 1, 2 fitted at both ends is folded in the shape of U on the central section, and is inserted into an external pipe 5 via a plurality of disc-shaped bearing bodies 4 arranged at almost equal pitches in the direction of the guide 3. Besides, to one side 3a of the wave guide 3, AE sound due to the changing state of ground can be directly transmitted, and to the other side 3b, the AE sound is not transmitted. Then, the AE sensors 1, 2 at both ends are connected to the detecting signal processing device 7. As a result, the AE sensors are used to be frequently collected and so they are economical and the reliability of measuring can be secured.

Description

[Detailed description of the invention] Industrial application field This invention predicts in advance a landslide on a natural slope or a collapse of the ground during excavation or cutting work, etc.
This article describes a ground deformation detection device using an acoustic emission (hereinafter abbreviated as AE) sensor, which is used to develop appropriate disaster prevention measures, and a ground deformation detection method that is implemented using this detection device.

Conventional technology It is important to predict landslides on natural slopes or collapse of the ground during excavation or cutting work, etc., in advance and take appropriate disaster prevention measures. It is necessary to detect the condition in half the time.

The following methods and means are known as conventional methods and means for detecting destruction and deformation of the ground.

■ Use a landslide meter to detect ground surface displacement.

■ Use inclinometers or subsidence meters to detect underground displacement.

■ As an ordinary AE detection method that utilizes acoustic emissions (AE), which are elastic waves generated due to deformation of the ground, as shown in Figure 8A, a waveguide 3 is buried underground; The AE sound transmitted through the waveguide 3 is received by the AE sensor 1. The AE sensor 1 detects the AE sound generated at the intersection point P with the slip line due to the deformation of the ground as shown in FIG. 8, and predicts destruction. In this case, as it is necessary to accurately evaluate the underground AE occurrence point (P position), as illustrated in Fig. 7,
A long linear waveguide 3 with AE sensors 1 and 2 attached to both ends is housed in an outer tube 4, buried underground, and the difference in arrival time of AE sound captured by AE sensors 1 and 2 at both ends is measured. Based on this, the location P of ground deformation is calculated and evaluated.

Problems to be Solved by the Present Invention The above-mentioned method (2) for detecting ground surface displacement can only detect ground surface displacement. Moreover, unless significant ground deformation occurs, it is often difficult to judge whether a dangerous phenomenon is occurring or whether it is simply a measurement error. Furthermore, since the detection device is linear, there is a problem in that it is likely to become an obstacle to work at a construction site.

A typical detection device for the underground displacement detection method described in (2) above is an inclinometer, but in general, insert-type inclinometers have to be lowered into the ground every time the measurement part is measured, making automatic measurement difficult. Measurement takes time. Although fixed-type inclinometers are capable of automatic measurement, they require extreme care when installing the detection device, have problems with the long-term reliability of a portion of the sensor, and are expensive.

According to the AE detection method shown in Figure 7 and mentioned in (2) above, it is possible to evaluate what kind of ground deformation has occurred underground and caused AE; Sometimes there is a fear that the AE sensor 2 at the tip will be damaged, and when removing it, the only option is to bury the AE sensor 2 underground, which is very uneconomical.Moreover, it is susceptible to the adverse effects of work noise and other noises. However, it has the disadvantage of poor practicality in terms of detection accuracy, which is a problem that needs to be solved.

Means for Solving the Problems As a means for solving the problems of the above-mentioned prior art, the first method is as follows.
The device for detecting ground deformation using an AE sensor according to the invention is, as shown in the embodiments in FIGS. The waveguide 3 is formed into a U-shape by bending the central part of its length, and the waveguide 3 has a large number of disk-shaped supports 4 arranged at approximately equal pitches in the length direction.
was inserted into the outer tube 5, which has approximately the same length as the U-shaped waveguide 3. One half 3a of the U-shaped waveguide 3 is configured so that the AE sound caused by the deformation of the ground is directly transmitted to the waveguide 3 via the support 4, and the other half 3b is caused by the deformation of the ground. It was supported by an intermediary that does not transmit any AE sound.

AE sensor at both ends 1. 2 is characterized in that a signal processing device 7 for the detection signal is connected thereto.

In addition, the method for detecting ground deformation using the AE sensor according to the second invention, as shown in the embodiments in FIGS. 1 to 6, uses the detection device 18 according to the first invention to 9, and the AE sound caused by the deformation of the ground 9 is transmitted to the AE sensor 1 at both ends of the waveguide 3. 2, and the AE sound generation position is calculated and evaluated based on the difference in arrival time of the AE sound received by the AE sensors 1.2 at both ends of the waveguide 3.

When a landslide as shown in FIG. 8B occurs on the target ground 9 on which the action detection device 8 is installed, an AE wave is generated at the intersection with the slip line and transmitted to the waveguide 3. That is,
The AE waves generated at the slip line are transmitted from the outer tube 5 to the support 4.
and is transmitted to the waveguide on one half 3a. Since the sound of the deformation of the ground is not transmitted to the other half 3b of the waveguide, there is no need to worry about noise being mixed in. The AE sound propagated to one half 3a is propagated toward both ends of the waveguide 3, and is transmitted to the AE sensor 1 at both ends. It is received by 2. Therefore, the propagation speed of the AE sound in the waveguide 3 and the total length of the waveguide 3 (AE sensor 1.
Since the distance between 2 and 2) is a known quantity, by measuring and processing the time difference of the AE multiplied signals that reach the AE sensors 1. This makes it possible to accurately determine and evaluate the presence or absence of symptoms and their location.

Example The illustrated invention will now be described in detail.

FIG. 1 shows the installation situation of the detection device ii8.

AE sensor 1 on both ends. The rod-shaped waveguide 3 to which the waveguide 2 is attached is bent at the center of its length to form a U-shape. This U-shaped waveguide 3 is formed such that one half 3a thereof has a length required for measuring ground deformation, for example, about 5 m or 10 m. It is important that the waveguide 3 is made of a material that has a rigidity as close as possible to that of the ground 9 to be measured, and in the illustrated example, reinforcing bars with a diameter of about 9 mm are used. In addition, depending on the properties of the target ground 9, the material may be changed, such as a glass fiber pipe or a polyvinyl chloride pipe filled with bubble mortar.

The U-shaped waveguide 3 is inserted into an outer tube 5 having approximately the same length as the U-shaped waveguide 3, thereby being protected so that ground deformation can be clearly detected.

A vinyl chloride vibrator or an iron vibrator having an outer diameter of approximately 50 to 70 mm is used as the outer tube 5, and a male portion 5a is provided at the tip thereof to facilitate embedding work.

The waveguide 3 is connected to the outer tube 5 via a large number of disk-shaped supports 4 (shape that follows the cross-sectional shape of the outer tube 5) arranged at approximately equal pitches in the length direction. It is well supported. It is important that the support 4 is made of a material that can easily transmit AE waves, and for example, a nylon disk is used. In particular, the waveguide 30 half 3a is
The outer tube 5 is designed so that the AE sound caused by the deformation of the ground 9 is directly transmitted to the waveguide 3& through the outer tube 5 and the support 4.
The relationship between the support body 4 and the support body 4 and the waveguide 3a is such that they are in perfect contact with each other.

However, between the other half 3a of the waveguide 3,
In order to prevent any AE sound from being transmitted due to the deformation of the ground 9,
It passes through a circular hole 4a that creates a gap of sufficient size to provide a non-contact structure. Therefore, over the entire length of the U-shaped waveguide 3, there is always one location where the AE sound is manually applied in response to the deformation of the ground 9.

Note that as a structure for creating a non-contact gap between the other half 3b of the waveguide 2 and the support body 4, a structure in which a U-shaped notch 4b is provided in the support body 4 as shown in FIG. 3A, Alternatively, as shown in FIG. 3B, the support body 4 can be configured to have a semicircular shape.

AE sensor 1 at both ends of waveguide 3. 2 is connected to a signal processing device 7 which has the function of processing the received AE sound detection signal, recording and storing the results, displaying images, and printing out the results. External AE sensors 10 and 11 are installed at both ends of the waveguide 3 at positions closer to the outside than the AE sensors 2, respectively, for detecting noise mixed in from the outside, and these are also connected to the signal processing device 7. ing.

In other words, in the case of this detection device 8, the signal processing device 7 includes:
Main AE sensor 1.2 and external AE sensor 10.
11, each detection signal is input manually. Then, the signal processing device 7 first performs data processing to remove the detection signal of the adjacent external AE sensor 10 (or 11) as noise from the detection signal of the AE sensor 1 (or 2). AE that occurred between and 2
Make only the sound clear, and perform the following calculation processing, for example.

1 of the length of waveguide 3 between AE sensors 1 and 2
/2 is L, and the depth of the underground AE sound generation position is x, AE
If the sound propagation speed is Vp, each AE sensor,
The time t1 and t2 until reaching 2 is tI=x/Vp
, t2=2L-x/Vp. Therefore, the arrival time difference t between the two is t” t2 t+=2
It is determined by the formula (L-x)/Vp. Therefore, x=
It is determined by the formula: L-1/2◆VP-t. Therefore, it is not affected by any adverse effects of noise.

As is clear from FIG. 1, the method of using the detection device 8 having the above configuration is as follows: First, a measurement hole 12 is drilled in the target ground 9 to the depth and direction necessary for measurement, and an outer tube is inserted into the measurement hole 12. 5. Insert the protected device body, and coat the outer periphery with cement milk 1.
3 to ensure integrity with the ground 9.

As an example of how to use the detection device 8 and the method of detecting ground deformation using the same, as shown in FIG. Detection is performed. Alternatively, in root cutting or mountain retaining excavation work as shown in FIG. 5, detection is performed by embedding the waveguide 3 on the ground side in a position that intersects with the slip line. Furthermore, as shown in FIG. 6, in order to measure the loosening of the ground such as a tunnel, a detection device 8 is buried in a range that covers the loosening zone. others,
The above-described detection device 8 and detection method can also be applied to detect deformation of structures such as slabs and columns.

As described in detail in conjunction with the embodiments above and beyond the effects of the present invention, the device and method for detecting ground deformation using an AE full sensor according to the present invention provides an AE full sensor.

Since AE sensor 2 is always on the ground surface, there is no need to worry about accidents such as damage to all AE sensors during installation, and AE sensor 1
．． 2 can be collected and used as many times as you like, making it a great 9! It is economical and has high measurement reliability. That is, 1t! ! Long-term stability and reliability of plate deformation measurement can be maintained by 5f.

In addition, it is possible to detect ground deformation with high precision by removing noise, and it is also possible to quantitatively and easily detect ground deformation based on the position and amount of deformation, so it is possible to quickly and reliably detect landslides or ground collapse in advance. This greatly contributes to predicting and developing appropriate disaster prevention measures.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view showing the state of use of the detection device according to the present invention, and FIGS.
■Cross-sectional views showing examples of configurations with different arrow views, Figures 4 to 6
The figure is a cross-sectional view showing different embodiments of the method for detecting ground deformation, Figure 7 is an elevational view showing an example of the use of a conventional detection device, and Figures 8A and B show the outline of the landslide detection method. FIG. 1, 2...All AE sensors 3...Wave guide 4...Support body 5...Outer tube 3a. 3b... Half of one side of the waveguide 7... Signal processing device 8... Detection device 9... Ground map

Claims (1)

[Scope of Claims] [1] A bar-shaped waveguide of a desired length with AE sensors attached to both ends is bent at the center of its length to form a U
The waveguide is shaped like a U-shape, and the waveguide passes through a large number of disc-shaped supports arranged at approximately equal pitches in its length direction into an outer tube that has approximately the same length as the U-shaped waveguide. One half of the U-shaped waveguide is inserted so that AE sound caused by deformation of the ground is directly transmitted to the waveguide via the support, and the other half is used to transmit AE sound caused by deformation of the ground. A ground deformation detection device using an AE sensor, characterized in that the AE sensor is supported in such a manner that no signal is transmitted thereto, and a signal processing device for the detection signal is connected to the AE sensor at both ends. [2] Claim 1, characterized in that an external AE sensor is mounted at a position further outward than the AE sensors at both ends of the waveguide, and this external AE sensor is also connected to a signal processing device. A ground deformation detection device using an AE sensor described in . [3] A bar-shaped waveguide of a desired length with AE sensors attached to both ends is bent at the center of its length to create a U
The waveguide is shaped like a U-shape, and the waveguide passes through a large number of disk-shaped supports arranged at approximately equal pitches in its length direction into an outer tube that has approximately the same length as the U-shaped waveguide. One half of the U-shaped waveguide is inserted so that AE sound caused by deformation of the ground is directly transmitted to the waveguide via the support, and the other half is used to transmit AE sound caused by deformation of the ground. A detection device with a configuration in which a signal processing device for the detection signal is connected to the AE sensor at both ends is buried in the target ground, and the AE sound caused by ground deformation is waveguided. A method for detecting ground deformation using an AE sensor, characterized in that the AE sensor detects ground deformation at both ends of the AE sensor, and calculates and evaluates the position where the AE sound is generated based on the difference in arrival time of the AE sound received by the AE sensor.