22 / 2023-05-14 12:40:22

Improvement of hardware and software-methodical means of express-assessment of burst-hazard during underground mining

burst hazard, safety risk identification, acoustic emission, geodynamic monitoring

Acoustic emission (AE) method of monitoring of mine workings is a promising geophysical method, which in recent years has received much attention.

This method has a number of advantages among which:

-operability of assessment of the geodynamic situation;

-possibility of developing and supplementing the complex criterion on the basis of the basic parameters of the AE pulses;

possibility of development of complex criterion on the base of main parameters of AE pulses; -localization of centers of increased rock pressure;

-possibility of reliable estimation in conditions of technological disturbances etc.

Local instrumental AE method is a part of the complex geodynamic monitoring and can act as a complement to the existing stationary control systems, as well as an independent method.

Acoustic method is based on registration and analysis of the main parameters of acoustic emission pulses that accompanies the process of loading and destruction of rocks.

The accumulated more than 10 years of experience in the development and operation of technical and methodological means of local control allowed to implement a layout of a new version of the device "Prognoz-L2". During the operation of the previous version of the device new solutions emerged aimed at expanding the technical capabilities to increase its potential.

For reliable assessment of mine workings condition the new version of the device includes: measuring the current noise level; dynamic thresholds of signal detection when measuring AE; visualization of the results and measurement process; viewing signalograms and signal parameters in real time; statistical parameters of the received AE signals; filter settings in manual and automatic modes; prompt change and addition of burst-hazard assessment criteria; user accounts; ability to play records and view results from In total more than 80 new working view screens and pop-up windows were developed.

Modernized version of the device "Prognoz-L2" is based on modern and advanced component base. Structurally the device consists of an in-house developed control board, wireless (Qi) charging unit and power organization with a built-in active barrier of intrinsically safe circuit, Raspberry Pi Zero W microcomputer board, IPS screen and Li-po rechargeable battery.

The device is used together with piezoceramic vibration transducers of AR2099-1000 series developed specially for Prognoz-L2 series and distinguished by high sensitivity, low self noise level, reliability, frequency response flatness in the range of 1-16 kHz.

The device housing is designed and manufactured from VG280 (polyurethane) with an increased resistance to mechanical and temperature influences. For mechanical protection, the housing construction contains elements in the elastic material VytaFlex60. The enclosure has a protection rating of IP 65.

The device uses a membrane keypad, which allows using the device in mining conditions, including in excavations with increased dustiness and humidity. The keyboard is resistant to mechanical impacts, sealed, resistant to petroleum products. The keyboard keys are made by membrane technology.

To display data and measurement process color IPS display with 800×480 pixels resolution and 4 inches diagonal is used. During the measurement process as well as at the end of the measurement the display of the device shows operational information and results in text and graphic form.

The most important and priority task was realization of new algorithms in the software shell under control of the open operating system Linux (UNIX).

At the software level, algorithms for reliable extraction of natural acoustic emission pulses in conditions of anthropogenic noise were developed, which are implemented by filters of four types of configuration:

-High-pass filter (HPF), allows to screen out pulses generated by heavy machinery, transport, drilling, as well as loading equipment.

Low-pass filter (LPF) allows to cut off impulses of both man-made and natural character, such as water dripping (including impulses generated by breakage of communication lines under pressure, as well as by operation of ventilation and other equipment generating high-frequency impulses.

-Bandpass filter (BF) allows parallel application of LPF and HPF with specified values.

-Band-eliminating filter (regressor filter), allows filtering of noise impulses with a certain value of frequency parameter, acting within the range of natural acoustic emission registration. These include pulses of mechanical origin during operation of conveyor, pump, compressor, etc. equipment.

Specificity of using the device assumes the presence of the operator in the burst-hazardous place for a long time (in the area of manifestation of mountain pressure). For safety in the device the remote listening of the audio stream by the operator through the wireless interface Bluetooth as well as the control and data exchange of the device with the external devices (headset, laptop, tablet PC) through the interface Wi-Fi is realized. This allows you to get the result and control the device during the measurement at a distance of up to 20 meters. Information about the results of measurements, as well as the history of the device is stored on the built-in memory card format micro-SD up to 128 GBytes. The device memory can hold up to 3000 measurements of 5 min each without unloading.

"Prognoz L2" passed industrial tests in the conditions of an underground mine, the patent of the new measuring instrument was received, as well as a certificate of compliance with the mine version (PH1 - mine normal).

Modernization of the local control device allows to realize more perfect algorithms of acoustic event parameters measurement, to increase reliability of their interpretation and analysis, to take into account complex technological conditions of monitoring, as well as to realize operatively additional criteria of burst-hazard assessment.