Research progress of acoustic emission signal and its application prospect in coal temperature sensing field

Acoustic emission signals have been widely used in the prediction of dynamic disasters such as rock burst, coal and gas outburst and large area roof pressure, in situ stress testing, rock stability evaluation and other fields. By referring to the mature monitoring principles and effective testing methods of acoustic emission technology, it can also quickly detect the temperature and other characteristic parameters in coal and rock mass, and is expected to be applied in the field of accurate detection of mine coal spontaneous combustion disaster. Through literature investigation, the research progress and application of acoustic emission signal in heterogeneous media, porous media and coal and rock mass are analyzed, summarized and elaborated. Through numerical simulation, mathematical modeling, to carry out the relevant characteristic variables control test and combining with reliable acoustic wave propagation theory in the research of the inhomogeneous medium, within porous medium and the coal and rock acoustic emission signal propagation characteristics and response parameters, and the results of study are applied to the damage detection, storage of grain temperature monitoring, mine dynamic disaster forecasting and other fields. The propagation characteristics and influencing factors of acoustic emission signals in different coal and rock masses are mainly analyzed, including coal and rock masses under different gas content, water content and pressure load. The processing and analysis method of acoustic emission signal is studied and summarized, because the hidden danger of coal spontaneous combustion in the mine will heat the coal and rock mass and the surrounding air to produce “burning sound”, and it will also be accompanied by certain environmental noise, to promote the acoustic emission signal processing and analysis technology to further perfect and systematic, the processing and analysis of AE signal characteristic parameters are organically combined with wavelet analysis and acoustic filtering algorithm, the technical idea of constructing acoustic emission signal characteristic parameter analysis and extraction algorithm is proposed to process acoustic signals. During the transmission process of acoustic emission signal in coal and rock mass, it is affected by many factors, such as physical properties of coal and rock mass, coal type, gas content, water content, etc., especially in the transmission process of loose coal mass, it is also affected by factors such as non-uniform temperature field formed by coal spontaneous combustion, coal block size, gas component concentration of coal spontaneous combustion, and porosity characteristics of loose coal mass. Combined with the theory of acoustics and coal spontaneous combustion, the application prospect of acoustic emission signal in monitoring coal temperature and warning coal spontaneous combustion disaster is prospected, experimental simulation and numerical simulation, as well as theoretical analysis and modeling, can be carried out according to the propagation and attenuation characteristics of acoustic emission signals in coal and rock for temperature inversion and reconstruction of uneven temperature field, which provides a new idea for solving the problem of accurate detection of fire sources in hidden space such as goaf. 