Geophysical Criterion of Pre-Outburst Crack Propagation in Coal Beds

The process of crack propagation in the coal face area is considered as an informative sign of coal and gas outburst hazard. In the known condition of crack growth at a certain distance from a coal face, it is suggested to replace mechanical parameters by geophysical data through application of different evaluation approaches: actual stresses-by spectral-acoustic method relative to amplitudes of high-frequency and low-frequency components of acoustic signal generated by mining machines in coal face area; pore pressure-by analysis of methane concentration in mine air in coal face area; strength of the most folded coal bed-by measuring strength based on penetration depth of a steel cone. The author analyzes the influence of acoustic, strength and permeability and porosity properties of coal face area on limit value of geophysical pre-outburst crack propagation criterion.