RU196545U1 - INSTALLATION FOR STUDYING THE DEPTH OF SENSITIVITY OF THE SPECTRAL-ACOUSTIC METHOD OF CONTROL OF THE STRESSED STATE - Google Patents

Abstract

The utility model relates to the field of non-destructive testing of the stress state of a rock mass, and in particular, to installations for studying the depth of sensitivity of the spectral-acoustic method for monitoring the stress state of a rock mass in front of a preparatory mine. The installation comprises a housing-container filled with a working medium, as well as an acoustic wave generator and a system for recording and analyzing acoustic signals. According to the proposed technical solution, the casing-container is made in such a way that it repeats the preparatory development on a given scale with its geometric shape, as well as the presence of an external frame, independent clamping elements, acoustic traps and sound-absorbing insulating material. 6 ill.

Description

The utility model relates to the field of non-destructive testing of the stress state of a mountain massif, and in particular, to installations for studying the depth of sensitivity of the spectral-acoustic method for monitoring the stress state of a mountain mass in front of a preparatory mine.

The spectral-acoustic method is based on the experimentally and analytically established fact of a stronger increase in the amplitudes of high-frequency harmonics in the noise spectrum of operating equipment compared to amplitudes of low-frequency harmonics when the bottom of the output approaches the zone of high voltage [1, 2].

In this method, the bottomhole space is probed by acoustic vibrations generated by the executive (cutting) body of the combine (or other working mechanisms: a plow, drilling rig, jackhammer or specially designed device). When using the method in the preparatory excavation, the acoustic oscillation receiver (geophone) is installed on the excavation board at a certain distance from the bottom.

It was experimentally established that, despite the fact that the geophone is behind the bottom of the face, the method allows you to fix the approach to the zone ahead of the face, which is dangerous in terms of the manifestation of dynamic phenomena. Moreover, the identified hazard, as shown by theoretical and experimental studies, when using this method is mainly due to increased stresses. However, there is currently no scientific justification for the depth of sensitivity of this method ahead of the preparatory development. Therefore, the proposed installation was developed and manufactured for modeling the stress state of the bottomhole space in front of the preparatory mine, sensing it with acoustic vibrations and receiving them with sensors installed behind the face.

According to the amplitude-frequency characteristic of the received acoustic signal, the relative stress coefficient is determined by the appropriate algorithms. The radius of sensitivity of the spectral-acoustic method will be determined by the number of the clamping element farthest from the bottom of the face, for which an increase in the coefficient of relative stresses will be recorded.

The closest technical solution for this purpose is a universal training and research stand studying the generation and propagation of acoustic waves in elements of industrial facilities from simulators of real sources of acoustic emission (Russian Patent No. 2608969. 2017. Bull. No. 4. / Rastegaev I.V., Danyuk A .V., Merson D.L., Vinogradov A.Yu.). The known technical solution consists of a model of a three-dimensional object, which is a container consisting of two elliptical or hemispherical bottoms and a cylindrical shell welded together and mounted on a support, as well as a manhole, a set of connecting fittings (fittings and valves), simulators of defects and their fasteners, loading device (compressor with receiver, accumulator, distributor, pressure sensors, valves, valves) and pipelines designed to fill the tank with liquid or gas a typical working environment, and systems for recording and analyzing acoustic signals.

For reasons that impede the achievement of the technical result indicated below, when using a known device adopted for the closest analogue, it includes:

- the model of the object is not a model of preparatory development;

- the model of the object does not provide for the presence of acoustic traps, so the sound, reflected from the walls of the model to complete attenuation, is superimposed on the main signal and distorts its amplitude-frequency characteristic;

- only liquid or gas can be used as a working medium;

- there is no possibility of a smooth change and movement of the stress field;

The objective of this utility model is to model the preparatory workings on a given scale while ensuring a smooth change in the stress field in the simulated bottom hole in front of the simulated preparatory workings from 0 to 5 MPa, with the possibility of adjusting the ratio between the maximum and minimum stresses in the range from 1 to 1.5; ensuring the displacement of the position of the zone of maximum of the generated voltage relative to the simulated breast of the working face to a distance of 0.2 to 1.4 of the width of the working discretely with a step equal to 0.2 of the width of the working; with the implementation of isolating the emitter of acoustic vibrations from the model body; suppressing reflected acoustic vibrations from the walls of the model due to the presence of acoustic traps around the entire perimeter of the model and covering the surface with sound-absorbing material; modeling by a source of acoustic vibrations of acoustic radiation (“noise”) of working mining equipment, in particular, a roadheader, which probes the bottomhole space; studying with the help of a system for recording and analyzing acoustic signals the influence of the removal of the simulated maximum of the reference pressure from the bottom of the output on the spectral composition of the “noise” of the working equipment, which will determine the sensitivity depth of the spectral-acoustic method for controlling the stress state.

The technical result of the proposed technical solution: modeling the stress state of the bottom hole in front of the preparatory mine and the acoustic radiation of the working tunneling machine in front and along the side of the preparatory mine for sensing the bottom hole by acoustic vibrations and their reception by sensors installed behind the bottom, as well as assessing the influence of the distance of the simulated reference maximum pressure from the bottom of the working on the spectral composition of the "noise" of the working borudovaniya by which it determines the sensitivity of the depth of the spectral-acoustic method of monitoring the state of stress.

The specified technical result is achieved by the fact that in the installation for studying the depth of sensitivity of the spectral-acoustic method for controlling the stress state, comprising a container body filled with a working medium, as well as an acoustic wave generator and a system for recording and analyzing acoustic signals, according to the proposed technical solution, the housing -Capacity is made in such a way that, with its geometric shape, it repeats the preparatory development on a given scale, as well as the presence of an external frame, without isimyh apart clamping elements, acoustic traps, and a sound-absorbing insulating material.

The claimed technical solution is illustrated by drawings, where in FIG. 1 shows an assembly in isometric view; in FIG. 2 - housing-capacity of the installation without a frame in isometry; in FIG. 3 - casing capacity of the installation without a frame on the side; in FIG. 4 - casing-installation capacity without a frame from the side in front; in FIG. 5 - sectional body; in FIG. 6 is a location diagram of transducers of acoustic vibrations into electric ones, from the outputs of which the signals are fed to the input of the system for recording and analyzing acoustic signals (not shown in the drawing).

The inventive device includes: an external frame 1, which supports and reinforces the functions of the installation housing 2. Clamping screws 3 are installed in the guide holes in the upper part of the frame. The installation housing is shown in more detail in FIG. 2-6. It consists of a bottom 4, covers 5-7, a cover of the pressure zone 8 and pressure elements 9. In the openings of the covers 6 and pressure elements 9, depending on the experimental conditions, either pressure sensors 10 or plugs 11 are installed. The bottom 4 may be both integral and collapsible, consisting of several parts. In this case, when assembled, the components must completely repeat the geometry of the whole variant. The bottom 4 and the covers 5 and 7, due to their special geometry, form acoustic traps 12 and 13 on the ends of the casing of the installation 2, which suppress reflected acoustic vibrations; and the bottom 4, the covers 6 and the covers of the zone of creating the necessary pressure 8 - form acoustic traps 14 and 15. In the wall 16 of the bottom 4, which simulates the chest of the bottom of the mine, there are two holes. Depending on the experimental conditions, either an acoustic oscillation generator 17 or a plug 18 are installed in them. The acoustic oscillation generator must not touch the unit body 2, therefore it is isolated from it by a gasket 19. Acoustic vibration transducers 21 are installed on board the production model 20 of the bottom 4 the signals from the outputs of which are fed to the input of the system for registration and analysis (not shown in the drawing). A pipe 22 is installed at the bottom of the bottom 4, with the irrigation system elements 23 mounted therein. The entire inner perimeter of the installation 2 body is covered with sound-absorbing material 24.

As a model material (the position in the drawings is not shown), for modeling the rock mass in the claimed technical solution, it is proposed to use sand. The acoustic properties (longitudinal and shear wave velocities, attenuation coefficient) of coals of various deposits are very different from each other [3]. Therefore, modeling material should allow these changes to be taken into account (implemented). This is achieved through the use of sand as a material simulating a coal seam, since the speed of acoustic waves of sand strongly (more than an order of magnitude) depends on humidity [4]. In addition, with increasing humidity, the bond between the sand particles increases, and the attenuation coefficient decreases.

и модели

(коэффициент подобия К_п) должно быть таким же, как соотношение длин волн в выработке λ_в и модели λ_м.In order to obtain data on the influence of the stress state in the bottomhole zone on the amplitude-frequency characteristic of the acoustic "noise" of the operating equipment, similar to those that would be obtained in a real mine, the frequency range for Models must be produced in accordance with the principle of similarity. In accordance with this principle, in order to maintain the conditions of sound propagation along the sides of the mine from the emitter to the receiver, similar to the real mine, the ratio of the width of the mine

and models

(similarity coefficient To _p ) should be the same as the ratio of wavelengths in the development of λ _in and model λ _m

To determine the similarity coefficient and the operating frequencies of the installation, we define the following initial data:

. Ширина модели горной выработки в заявляемом техническом решении задается в соответствии с выбранным масштабным коэффициентом. Для примера, возьмем соотношение размеров ширины моделируемой и реальной подготовительной выработки 1:20. Тогда ширина модели горной выработки в заявляемом техническом решении будет равна

1. The width of the real mine in the middle part: 3-5 m. Therefore, we accept

. The width of the model of mining in the claimed technical solution is set in accordance with the selected scale factor. For an example, we will take a ratio of the sizes of width of the modeled and real preparatory development 1:20. Then the width of the model of mining in the claimed technical solution will be equal to

2. The range of recorded frequencies ƒ _{in the} apparatus for predicting dynamic phenomena by the spectral-acoustic method, for example, SAKSM: 20-3500 Hz.

3. The velocity of longitudinal sound in the angle С _у ≈ 3000 m / s [1].

4. The speed of longitudinal sound in sand, C _m, strongly depends on its humidity [2] and for a non-saturated state varies between 200-700 m / s.

For the adopted conditions, the similarity coefficient To _n will be equal to:

where λ _m and λ _in - respectively, the wavelength in the model and in the development, m

The wavelength in the development of λ _in equal to:

where C _y is the speed of sound in the corner.

Then from (1) we have:

The radiation frequency in the model ƒ _m is equal to:

Taking into account possible changes in the speed of sound, we believe that the possible frequency range in the model is in the range of 20-20000 Hz. The inventive device operates as follows:

1. make the installation of the housing-capacity 2 in the outer frame 1;

2. with the covers 5-7 open, and the covers of the pressure injection zone 8, model material imitating a rock mass is loaded into the bottom 4 of the housing 2 (sand; the position in the drawings is not shown conventionally);

3. close the lids 5-8 and install the clamping elements 9;

4. install pressure sensors 10 and make their connection to power sources and recording equipment (not shown in the drawing) and plugs 11;

5. the clamping screws 3 are installed in the outer frame 1 and they are screwed in alternately until they are in contact with the covers 6 or with the clamping elements 9, after which they are tightened by one revolution of the clamping screw 3 to create resistance to opening during the experiment;

6. install the generator of acoustic vibrations 17 in one of the holes on the wall simulating the chest of the face, put a plug in the second hole of this wall, and install transducers of acoustic vibrations 21;

7. check the safety, conduct a performance assessment and configure all electrical systems;

8. pipeline 22 through a pump is connected to a water supply system (tank);

9. pre-tighten the clamping screws 3 and make sure that the pressure sensors 10 installed under the covers 6 and clamping elements 9, record the pressure change;

10. under the covers 6 set the pressure to 2-3 MPa and keep it constant during the experiment;

11. when the generator of acoustic vibrations is turned off, the amplitude of the signals recorded from the transducers of acoustic vibrations 21 is recorded in time;

12. The maximum value of the measured amplitude is taken as the level of acoustic noise; in order to reduce it, choose such a place for installation, next to which there are no working mechanisms emitting acoustic vibrations;

13. turn on the acoustic oscillation generator 17 and produce an increase in pressure in front of the simulated mine for all clamping elements 9 by tightening the clamping screws 3 to create an uneven stress state in front of the bottom face of the mine; while the sand with which the casing of installation 3 is filled must be dry, with a relative humidity of 1-2%;

14. from the transducers of acoustic vibrations 21 remove the amplitude-frequency characteristic (AFC) of the acoustic signal;

15. an increase in pressure under the clamping elements 9 is performed discretely in increments of 1 MPa up to a maximum pressure of 5 MPa; at each stage of the pressure rise carry out exposure for 5 minutes and analyze the amplitude-frequency characteristic of the acoustic signal; then the pressure is raised to the next stage and the amplitude-frequency characteristic of the acoustic signal is analyzed again;

16. the pressure under each of the clamping elements 9 is set so that as you move away from the bottom of the bottom of the working model, the pressure increases by 0.7 MPa, starting from 0.8 MPa under the first clamping element 9 and up to 5.0 MPa under the seventh clamping element 9;

17. The measurement and control of pressure throughout the entire process of loading the installation is carried out using pressure sensors 10;

18. in the event that on some sensors-transducers of acoustic vibrations 21 the signal amplitude is too small (close to the noise level), the sand is moistened by 1-2%, by supplying water to the pipe 22, and the frequency response is removed again;

19. The sand is humidified until a signal is detected whose amplitude exceeds at least 3 times the interference amplitude;

20. by tightening and loosening the clamping screws 3, the necessary stress diagrams are created in the model of the bottomhole space, in accordance with the experimental conditions and repeat paragraphs. 15-20;

21. to study the effect of sound diffraction in the area adjacent to the bottom of the mine with its side on the sensitivity depth of the spectral-acoustic method, the acoustic oscillator 17 and the plug 18 are interchanged.

The claimed technical solution allows:

- simulate preparatory development on a given scale;

- create acoustic radiation in it, the parameters of which are set in accordance with the principle of similarity to the similar parameters of the acoustic radiation of a working tunneling machine in a real output;

- register acoustic radiation with sensors behind the simulated working face;

- to provide a smooth change in the stress field in the simulated bottomhole space in front of the simulated preparatory mine from 0 to 5 MPa, with the ability to adjust the relationship between the maximum and minimum stresses in the range from 1 to 1.5;

- to ensure the displacement of the position of the zone of maximum of the generated voltage relative to the simulated breast of the working face at a distance of 0.2 to 1.4 of the working width discretely with a step equal to 0.2 of the working width.

- minimize the influence of external factors on the studied acoustic signal;

- the amplitude-frequency characteristic of the received acoustic signal according to the appropriate algorithms to determine the relative stress coefficient;

- determine the radius of sensitivity of the spectral-acoustic method by the distance from the bottom of the mine to the most distant clamping element, for which an increase in the coefficient of relative stresses with growth will be recorded.

List of sources

1. Mirer S.V. Spectral-acoustic forecast of outburst hazard of coal seams / S.V. Mirer, O.I. Khmara, A.V. Shadrin. - M. - Kemerovo: Kuzbassvuzizdat, 1999 .-- 92 p.

2. Shadrin A.V. A comparative analysis of the spectral-acoustic method for predicting dynamic phenomena / A.V. Shadrin, A.A. Kontrimas, A.S. Teleguz // High-tech technologies for the development and use of mineral resources: scientific. Journal / Sib. state industry un-t; under the general ed. V.N. Fryanova. - Novokuznetsk, 2018. - No. 4. C 370-375.

3. Azarov N.Ya. Seismoacoustic method for predicting mining and geological conditions for the exploitation of coal deposits / N.Ya. Azarov, D.V. Yakovlev. - M: Nedra, 1988 .-- 199 p.

4. Lyakhovitsky F.M. Engineering Geophysics / F.M. Lyakhovitsky, V.K. Khmelevsky, Z.G. Yashchenko. - M .: Nedra, 1989 .-- 251 p.

Claims (1)

Installation for studying the depth of sensitivity of the spectral-acoustic method for monitoring the stress state, comprising a housing-container filled with a working medium, as well as an acoustic wave generator and a system for recording and analyzing acoustic signals, characterized in that the housing-container is made in such a way that its geometric in form, it repeats the preparatory development on a given scale, as well as the presence of an external frame, independent clamping elements, acoustic traps and sound absorbing insulating material.

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