# Statistical Analysis of Acoustic Emission in Uniaxial Compression of Tectonic and Non-Tectonic Coal
)1 State Key Laboratory of Coal Mine Disaster Dynamics and Control, Chongqing University, Chongqing 4000044, China; [EMAIL_ADDRESS] (Y.Z. )1 State Key Laboratory of Coal Mine Disaster Dynamics and Control, Chongqing University, Chongqing 400044, China; [EMAIL_ADDRESS] (Y.Z. )1 State Key Laboratory of Coal Mine Disaster Dynamics and Control, Chongqing University, Chongqing 400044, China; [EMAIL_ADDRESS] (Y.Z. )1 State Key Laboratory of Coal Mine Disaster Dynamics and Control, Chongqing University, Chongqing 400044, China; yoyaheyi@cqu. extreme fragmentation of particles can block micro-fractures in the coal and cause low permeability. In addition, this interval broken structure causes a lower mechanical stability in tectonic coal relative to non-tectonic coal. The tectonic coal layer is more prone to breaking under the impact of external factors, such as crustal stress, gas pressure, and explosion. This breakage causes internal coal and gas outburst and other coal mine disasters [9; 10]. The presence of tectonic coal complicates the occurrence of gas and leads to considerable deviation in traditional gas forecasting methods. The existing data indicate that essentially all coal and gas outburst seams have developed tectonic coal with a certain thickness. In addition, the majority of initial outburst points occur near tectonic coal. Many studies have focused on the genesis, evolution, physical structure, and storage properties of tectonic coal [11; 12]. Due to the need for coal-bed exploration and development, the storage properties of tectonic coal are often studied. These storage properties include the porosity, permeability, absorption, and desorption properties of tectonic coal [13; 14]. However, the effective disaster prediction method for tectonic coal collapse is rare. Although some geophysical seismological methods have been introduced into mine safety prevention, the related coal and gas outburst disaster still appears. The most common field monitoring method is acoustic solution, such as acoustic emission (AE). The AE technique is based on monitoring the elastic waves generated by propagating and expanding micro cracks. Due to stress and other factors, a certain point in the material will break and release the elastic wave. The surface of the material will be captured by an AE probe as the elastic wave propagates. There are some standard parameters that contain plentiful information regarding the microstructure, and the physics background of AE techniques which have been described [15]. Recently, sudden disasters have been investigated by statistical physics, especially for earthquake and avalanche [16; 17]. From the perspective of statistical physics, the catastrophic events share a similar dynamic evolution and without characteristic scale, which means that statistical rules work in different scales, like earthquake and rock sample failure in the laboratory [18]. Indeed, this robust similarity has been confirmed by earthquake catalog and silica glass failure [19]. In laboratory research, AE was usually adopted to investigate the statistical physical behaviors of porous material collapse [20]. Previous results showed that the probability distribution is related to the porous material's damage situation [21; 22]. Sandstone uniaxial collapse shows that the distribution exponents change from a non-critical steady state to an all-important precursor regime, which means that the prediction of the collapse is possible in principle [23]. This agrees well with discrete element computer simulations [24; 25]. The tectonic coal could be seen as one kind of mechanical and thermal-damaged coal, and the probability distribution of AE should reflect the structural difference between tectonic and non-tectonic coal. Therefore, in this study, we introduce the probability density distribution of AE, and the multifractal of AE location points to investigate the deformation and failure process of tectonic and non-tectonic coal under uniaxial compression.