Study on microstructure characteristics of material evidence in coal dust explosion and its significance in accident investigation

The weakness of material evidence analysis brings challenges and problems to the investigation of mine gas and coal dust explosion accidents. As an important material evidence, post-explosion coal dusts contain rich information about explosion process and reaction mechanisms and can play an important role in explosion accident investigation. The study uses image processing technology and fractal theory to make qualitative and quantitative characterization of microstructure of post-explosion coal dusts and discuss its significance in mine explosion accidents investigation. Regular spherical residues particles were unique for post-explosion coal dusts and various explosion residue particles could be broadly classified into four types. Quantitative analysis suggests that the particle size distribution of post-explosion coal dusts exhibits fractal property and has smaller fractal dimensions due to the increase of fine particles and coarse particles. The roundness of explosion residues is larger than that of original coal dusts and has a negative correlation with particle size. It is also found that the isothermal adsorption-desorption curves of post-explosion coal dusts could be classified into Type II and are characterised by hysteresis loops of Type H3. The change laws of D-1 and D-2, two fractal dimensions obtained by using FHH method, indicate that post-explosion coal dusts have more irregular pore surface and more homogeneous pore structure. In addition, the present research work demonstrates that post-explosion coal dusts have application value in justifying the participation of coal dusts in mine explosion accident and deducing the explosion source.