RU1774303C - Recorder of electromagnetic radiation at fractures - Google Patents

Abstract

Usage: in the field of mining to control the destruction of sections of the rock mass when changing its stress-strain state, i.e. to provide a safe working environment for miners by registering electromagnetic radiation signals from the array to the antenna. The device includes a ferrite core with a winding evenly placed on it and a metal screen mounted on it. The ferrite core is made in the form of a torus, completely filled with a winding with its positioning and closing at an angle of 285-295 °; screen. At the same time, on the remaining open part of the winding, an additional visor is installed in the form of a horn with a bell outward. The side walls of the horn form an angle of not more than 65-75 °. 1 ill.

Description

The invention relates to mining and can be used to control the destruction of sections of a rock mass when changing their stress-strain state.

A sensor for electrical exploration equipment is known, including a solenoid with a core and an additional conductive rod located in the central part of the closed magnetic circuit. This sensor has the following disadvantages. In this design, the sensitivity of the sensor is enhanced by the concentration of the electromagnetic field between the solenoid and the shaft. This design of the sensor, firstly, does not allow registration of the signal outside the space of the solenoid, but

secondly, it does not register electromagnetic signals of small amplitudes with levels characteristic of signals coming from a rock mass. In addition, the sensor does not allow location of the place of occurrence of cracks and the direction of their propagation.

The closest analogue in technical essence and the achieved result is a device for detecting electromagnetic radiation arising from crack formation of rocks. The device includes a ferrite core with a winding wound on it, on which a metal screen is mounted.

The disadvantages of the latter device are as follows. EMP signals arising

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during formation of rocks, the rocks propagate in the direction of movement of the main crack. At the same time, the antenna pattern has two elongated lobes, which makes it possible to achieve high accuracy when locating the location and direction of propagation of cracks in a rock mass. Another disadvantage is the presence of two mutually perpendicular rods. This design is inconvenient to use especially in mine conditions.

The aim of the invention is to increase the focus of reception.

This goal is achieved in that the device for detecting electromagnetic (EMP) radiation arising from crack formation includes a ferrite toroidal core on which the winding is uniformly wound. A metal screen is installed on the winding, closing the latter at an angle of 285-295 °, while on the remaining open part the winding is surrounded by a metal stop, the axis of which is directed radially relative to the core, and the side walls are also located along the torus radii and form an angle within 65 .. , 75 °.

The physical prerequisites for carrying out the invention are as follows.

The presence of a metal screen on the winding of the toroidal core allows the magnetic flux lines to be pressed, concentrating them in the space between the signal winding and the screen. Outside the screen, the magnetic field lines are displaced into the surrounding space and the antenna pattern is formed in the form of narrow lobes. This effect significantly increases the sensitivity of the receiving device, which makes it possible to register signals of weak electromagnetic fields arising from germinating cracks. The installation of a visor in the form of a horn on the open part of the winding makes it possible to reduce the intensity of the internal (rear) antenna petals. This effect, while maintaining the high sensitivity of the receiving equipment, allows location of the place of occurrence and direction of propagation of cracks.

The drawing shows a device for detecting electromagnetic radiation during cracking, a general view, with a corresponding radiation pattern (dashed lines).

The device for detecting electromagnetic radiation during cracking consists of a ferrite toroidal core 1 with a winding 2 wound thereon and a metal shield 3 covering the winding 2 partially at an angle of 285-295 °. The remaining part of the winding 2 that is open is covered by a metal horn 4, the axis of which is directed radially with respect to the core 1, and the side walls 5 form an angle in the range of 65-75 °.

The operation of the device is illustrated by the example of crack control in

mass of rocks with the introduction of underground mining. Dynamic phenomena occur in the array, associated with high mechanical stresses, accompanied by intensive destruction of the rock, which, in turn, is a source of electromagnetic radiation. In this connection, an important question for mining practice is the question of the place of occurrence and the preferred direction of propagation of cracks arising in the array, which, generally speaking, can propagate in different directions from the source, and the amplitudes of such signals are quite small.

about 10 uV. To locate such small signals, it is necessary to ensure high sensitivity, as well as minimize the intensity of reception of EMP signals by the back (or internal) lobes

antenna patterns,

The installation of a metal screen 3 on a winding 2 covering it in FIG. 285-295 °, allows you to get maximum sensitivity at the reception, which ensures the location of small amplitude signals. Decreasing the sensitivity by increasing small or decreasing the angle of closure of the windings does not allow to locate signals of small amplitudes. The working interval on the graph should be selected so as to provide the necessary sensitivity. For this, it is convenient to take the points of transition of straight sections of the branches of the graph into curved ones beyond the boundaries of the working interval of the graph with almost straight branches. Point A corresponds to an angle of 285 °, and point B corresponds to an angle of 295 °, the maximum signal amplitude is reached at 290 °; a decrease in the sensitivity of the device within 285-295 ° does not exceed 3%.

In the area of the array threatened by dynamic development along the workings, the section is profiled, for example, after 15 m. In this case, the measuring device places the bells outward, each time measuring the signal level on the recording device (not shown in the drawing) at the starboard and port side generation, marking the signal level each time.

At the highest signal level, for example, on the starboard side, the source of cracks is located, moving the device from right to left and from top to bottom and maximizing the signal on the recording device.

An advantage of the claimed device in comparison with the known one is an increase in the accuracy of the location of EMR signals.

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Claims (1)

SUMMARY OF THE INVENTION A device for detecting electromagnetic radiation during crack formation, comprising a ferrite core with a winding wound uniformly and placed in a metal screen, characterized in that, in order to increase the directivity of reception, the ferrite core has a torus shape, and the screen partially covers the winding with the open part of the winding covered by a metal horn whose axis is directed radially with respect to the core, and the side walls are also located along the radii of the torus and form an angle within 65 ... 75 °.