JPH0224521A - Apparatus for predicting collapse of natural ground - Google Patents

Abstract

PURPOSE:To predict the collapse of natural ground by sensing the deformation of the natural ground with an AE sensor based on an acoustic emission (AE) phenomenon, and analyzing the output with a computer. CONSTITUTION:The deformation of natural ground E is sensed with an AE sensor 2 based on an AE phenomenon. Noises are removed through a filter 3. Thereafter, the signal is amplified in an amplifier 4. The signal is sent into an AE counter 5 and a waveform transmitting device 6. In the AE counter 5, only the AE signal having the amplitude of a preset value or more is counted. At the same time, the waveform data from the AE sensor 2 are digitalized in the AE sensor 2. The obtained counted data and waveform data are sent into a microcomputer 7, and recorded. At the same time, the characteristics of the signal, the occurring frequency of the signals, the waveform data and the like are analyzed in accordance with a program which is imparted beforehand, and the collapse of the natural ground is predicted.

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention is a rock collapse prediction device used for safe work while monitoring rock collapse in civil engineering work where rock collapse is expected. This is related to.

(Conventional technology) In civil engineering work where the collapse of the ground is expected, construction work is carried out while measuring the deformation of the ground to ensure safe work.

However, early prediction has been extremely difficult because the precursory phenomena when a rock collapses do not necessarily appear in the form of significant EJI displacements on the ground surface or underground. In particular, it was difficult to predict sudden collapses, making it impossible to take necessary disaster prevention measures.

In civil engineering work, where the stability of the ground is initially disrupted by excavation, etc., as the work progresses, it becomes impossible to maintain the balance of the ground at any stage. We need to predict what will happen.

Conventionally, the main method used to detect such changes in the ground has been to measure the deformation of the ground, but in the early stages when the balance of the ground begins to be disrupted, Early prediction has been extremely difficult because changes within the body do not appear in any noticeable way.

FIG. 4 shows a conventional rock collapse prediction device.

i) The ground surface displacement meter is connected with a piano wire (a) between the two points A and B of the ground.
) and measure the displacement of the interval between the two points with a displacement needle (x) to understand the movement status of the ground. At this time, the position where the displacement meter (X) is set needs to be a fixed point where the ground is not moving.

ii) The underground displacement meter has the same principle as the ground surface displacement meter described above, and a steel wire (b) is stretched between two underground points A' and B', and the displacement between the two points is measured underground. Measure with a displacement meter (■).

ii) Mainly to estimate the position of the slip surface C, an inclinometer (Z) that measures the inclination angle is inserted into a pipe (0) installed vertically underground, and from the measured value of the inclinometer Calculate the amount of underground deformation.

As described above, conventional methods have been used to measure ground surface displacement and underground displacement using ground surface displacement meters, underground displacement meters, and inclinometers.

(Problems to be Solved by the Invention) When a collapsing rock is considered to be a large mass, the amount of displacement measured by the conventional displacement meter is macroscopic. It is thought that such macroscopic deformation appears as a result of the accumulation of microscopic cracks and deformations that occur inside the rock.

Therefore, at the very early stage when the ground collapses,
It can be assumed that the degree of disturbance in the balance of forces is small, and that macroscopic changes such as the movement of the entire ground begin to appear only after microscopic changes have accumulated to a considerable extent.

Therefore, it has been difficult to detect ground collapse at an early stage using conventional monitoring systems based on displacement measurement. In particular, the current situation is that it is very difficult to make predictions based on displacement measurements, especially in rocks made of soft rock with many cracks, which show only very small displacements before collapse, and often collapse suddenly.

The present invention was proposed in view of the above-mentioned conventional problems, and
The purpose is to provide a rock collapse prediction device that can detect signs of rock collapse as early as possible and prevent disasters from occurring.

(Means for Solving the Problems) In order to achieve the above-mentioned object, the rock collapse prediction device according to the present invention uses an acoustic emission system in which sound energy is emitted as a result of cracks and displacements occurring inside the rock. It was proposed with a focus on the phenomenon (hereinafter referred to as AE), and is similar to an acoustic emission sensor that is installed inside the ground or on a member that penetrates the ground and detects the deformation of the ground and converts it into an electrical signal. It consists of a counting circuit for acoustic emission electrical signals connected to a sensor, and a computer that inputs and analyzes the count data from the counting circuit to predict rock collapse.

Further, in the present invention, in order to remove ambient noise from the electrical signal of the AE sensor, a filter for removing ambient noise from the electrical signal is interposed between the acoustic emission sensor and the acoustic emission electrical signal counting circuit. It is composed of

(Function) Since the present invention is configured as described above, the AE sensor detects the deformation of the ground by the AE phenomenon, and the AE sensor converts the weak vibrations propagating through the solid body into an electrical signal. A claim in which the frequency of occurrence of the AE multiplied signal is counted by an AE multiplied signal counting circuit connected to the A sensor and inputted to a computer, and the computer analyzes this input signal to characterize the collapse of the ground. In the second invention, ambient noise is removed from the electrical signal from the AE sensor by a filter interposed between the AE sensor and the AE multiplied signal counting circuit, and the AE multiplied signal is sent to the counting circuit.

(Example) The present invention will be described below with reference to the illustrated embodiments.

When the ground remains stable, a polling hole (1) is dug and an AE sensor (2) is installed at a predetermined position within the polling hole (1).

The AE sensor (2) includes a filter (3) and an amplifier (
4) is connected, the amplifier (4) is connected to an AE counter (5) and a waveform transmission device (6), and the waveform transmission device (6) and the counter (5) are connected to a computer (7).
It is connected to the.

The AE sensor (2) is connected by a cable (8) to the filter (3), amplifier (4), AE counter (5), and waveform transmission device (5) installed in the observation hut (9). There is.

The installation location of the AE sensor (2) can be determined depending on the condition of the ground (E).

Since the illustrated embodiment is configured as described above, the deformation of the ground is detected by the AE sensor (2) using the AE phenomenon.
The AE sensor (2) converts the weak vibrations propagating through the solid into an electrical signal, which is then sent to the filter (3).
This eliminates noise from heavy machinery during construction work, etc., from the AE multiplied signal from this AE sensor (2).

The filter (3) is configured to remove signals of 1KH2 or less through a bypass filter, since most of the noise from heavy machinery OI during construction has a frequency of 1KH2 or less.

The AE signal from the AE sensor (2) from which noise has been removed by the filter (3) is amplified by the AE multiplier signal amplifier (4) and sent to the AE counter (5) and the waveform transmission device (6),
A with an amplitude greater than the set value in the AE counter (5)
It is counted only when the E-fold signal passes, and thus the AE counter (5) counts the frequency of occurrence of the AE-fold signal.

At the same time, using the waveform transmission device (6), the amplifier (4)
The amplified waveform data from the AE sensor (2) is digitized.

In this way, the AE counter (5) and the waveform transmission device (6)
) The amplified AE multiplied signal count data and waveform data obtained by the microcomputer (7)
At the same time as the signal is sent to and recorded, a program given in advance analyzes the characteristics of the signal, its frequency of occurrence, waveform data, etc. to predict the collapse of the ground.

In the figure, (F) is the slip surface.

Note that the AE sensor (2) may be attached to the above-ground portion of the reinforcing steel rod (11) that has penetrated the ground.

(See Figure 2) (Effects of the Invention) According to the present invention, as described above, the AE sensor installed in the ground or on the ground penetrating member can be
It is connected to the E signal counting circuit, calculates the frequency of occurrence of the AE multiplied signal, and transmits the count data to a microcomputer, which detects and analyzes the characteristics and frequency of occurrence of the AE multiplied signal. In addition to detecting collapse at its very early stage, it is possible to determine the extent of the collapse of the ground and the position of the slip surface, using data such as conventionally used displacement meter measurements and the device of the present invention. By comprehensively evaluating the obtained data, it is possible to predict rock failure with higher accuracy, and construction work can be carried out safely.

The invention as claimed in claim 2 provides for more accurate rock collapse prediction by interposing a filter between the AE sensor and the A-min signal counting circuit to remove ambient noise from the AE multiplied signal. This is what makes it possible.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of one embodiment of the rock collapse prediction device according to the present invention, FIG. 2 is a block diagram of another embodiment of the present invention,
FIG. 3 is a perspective view showing the practical state of the present invention, and FIG. 4 is a reduced sectional view showing a conventional rock failure prediction device. (2)-A E sensor (3)-Filter (4)
・-Amplifier (5)...-AE counter (6)-
Waveform transmission device (7) - Microcomputer - (E) - Jiyama agent Patent attorney Shige Okamoto 2 outsiders Figure 3

Claims (1)

[Scope of Claims] 1. An acoustic emission sensor disposed within the ground or on a member penetrating the ground, which detects deformation of the ground and converts it into an electrical signal, and an acoustic emission sensor connected to the sensor. A rock collapse prediction device characterized by comprising a counting circuit for a query electric signal and a computer that inputs and analyzes the count data of the counting circuit to predict a rock collapse. 2. The rock collapse prediction device according to claim 1, further comprising a filter interposed between the acoustic emission sensor and the acoustic emission electric signal counting circuit for removing ambient noise from the electric signal. .